Program
 
Mon Mar 08 2021
17:00 - 18:30
Science for Energy Policy Invited Speaker
 
Tue Mar 09 2021
10:30 - 10:35
CHEMNC Opening nanoGe
10:30 - 10:35
DSSC Opening nanoGe
10:30 - 10:35
NanoLight Opening nanoGe
10:30 - 10:35
PERIMPED Opening nanoGe
10:30 - 10:35
SOLFUL Opening nanoGe
10:30 - 10:35
TINPERO Opening nanoGe
10:35 - 10:45
CHEMNC Session Introduction 1.1
10:35 - 10:45
DSSC Session Introduction 1.1
10:35 - 10:45
NanoLight Session 1.1 Introduction by Sascha Feldmann
10:35 - 10:45
PERIMPED Session Introduction 1.1
10:35 - 10:45
SOLFUL Session Introduction 1.1
10:35 - 10:45
TINPERO Session Introduction 1.1
CHEMNC 1.1
Chair: Loredana Protesescu
10:45 - 11:05
1.1-I1
Scheele, Marcus
University of Tuebingen, Germany
Passivation and Functionality – the Dual Purpose of Organic Fluorophores as Ligands for Inorganic Semiconductor Nanocrystals
Scheele, Marcus
University of Tuebingen, Germany, DE
Authors
Marcus Scheele a
Affiliations
a, University of Tuebingen, Germany, Auf der Morgenstelle, 18, Tübingen, DE
Abstract

Coupled organic-inorganic nanostructures are hybrid nanocomposites consisting of inorganic quantum dots and organic fluorophores, which exchange significant electron density or energy across their mutual interface. As charge carriers or energy are exchanged, fundamental questions arise as to the direction, the efficiency and the speed of this transfer. Since exchanged charges carry magnetic momentum, another important question is the nature and fate of their spin in the process. The lifetime, dipole strength and degeneracy of excitons with different spin configurations are so distinct in inorganic vs. organic matter that the hybrid interface becomes a unique feature in any nanocomposite where emergent optoelectronic properties can occur.[1]

This presentation will detail how advances in the chemistry of nanocomposites, particularly the ability to graft organic fluorophores directly to the surface of inorganic nanostructures, enable the rational design of such hybrid materials.[2] Several examples will be presented where this has led to the emergence of novel optoelectronic behavior.[3-5] To name just one study, we have recently assembled CdSe nanocrystals with an aryleneethynylene derivative into a hybrid nanocomposite and studied energy transfer between both fluorophores. Many aryleneethynylenes exhibit aggregation-induced emission and a strongly structure-dependent fluorescence behavior.[6] We found that utilizing aryleneethynylenes as surface ligands for CdSe nanocrystals leads to periodic fluorescence oscillations with tunable resonance frequencies on a time scale of tens of seconds. The presentation will highlight the pivotal role of structure-dependent energy transfer within the nanocomposite in this respect.

11:05 - 11:25
1.1-I2
Bodnarchuk, Maryna
EMPA - Swiss Federal Laboratories for Materials Science and Technology
Surface Chemistry of Colloidal Cesium Lead Halides Perovskite Nanocrystals
Bodnarchuk, Maryna
EMPA - Swiss Federal Laboratories for Materials Science and Technology, CH
Authors
Maryna Bodnarchuk a, b
Affiliations
a, Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Überlandstrasse 129, CH-8600, Switzerland
b, ETH – Swiss Federal Institute of Technology Zürich, Department of Chemistry and Applied Biosciences, Laboratory of Inorganic Chemistry, Zürich, Switzerland
Abstract

Colloidal organic/inorganic lead halide perovskite nanocrystals (NCs) have become a popular class of light emitters for applications in the next-generation LEDs and LCD displays. High photoluminescence (PL) of these materials is achieved without the necessity for electronic surface passivation with epitaxial shells. The major practical bottleneck of these materials relates to their labile surface chemistry. In particular, typically used long-chain capping ligands such as oleic acid and oleylamine are problematic due to their dynamic and loose binding, leading to reduced chemical and structural integrity of NCs and hampering isolation, purification and applications of these NCs. Ligand loss also causes damage to the surface region of the perovskite NCs, seen as reduced PL quantum yield. We will discuss various alternative surface chemistry approaches, allowing to preserve or restore the surface structure. Healing of the surface trap states requires rebuilding of all damaged PbX6 octahedra and establishing a stable outer ligand shell. The efficiency of such an approach, seen as an increase in the luminescence quantum efficiency and improvement in the overall robustness of CsPbBr3 NCs, was attained using a facile post-synthetic treatment with a PbBr2+DDAB (didodecyldimethylammonium bromimde) mixture [1]. DDAB can be also used as a sole ligand directly in the synthesis of perovskite NCs that leads to the improved performance of LEDs [2]. We have also recently shown that long-chain zwitterionic ligands such as sulfobetaine or natural lecithin bind tightly to the surface of perovskite NCs and hence improved colloidal stability, which is retained also after multiple steps of isolation and purification [3,4]. Monodisperse NCs readily form diverse long-range ordered NC superlattices, exhibiting superfluorescent emission at cryogenic temperatures.

11:25 - 11:45
1.1-I3
Infante, Ivan
Istituto Italiano di Tecnologia (IIT)
Ligand Engineering in Colloidal Semiconductor Nanocrystals
Infante, Ivan
Istituto Italiano di Tecnologia (IIT), IT
Authors
Ivan Infante a
Affiliations
a, Istituto Italiano di Tecnologia (IIT), IT
Abstract

Next-generation colloidal semiconductor nanocrystals that features enhanced opto-electronic properties and processability are expected to arise from the complete mastering of the nanocrystals surface characteristics, attained by a rational engineering of the passivating ligands. The aspect is highly challenging as it underlies a detailed understanding of the critical chemical processes that occur at the nanocrystal/ligands/solvent interface, a task that is prohibitive due to the limited number of nanocrystals syntheses that could be tried in the lab. This challenging goal can however be addressed nowadays by combining experiments with atomistic calculations and machine learning algorithms. In the last decades we indeed witnessed major advances in the development and application of computational software dedicated to the solution of the electronic structure problem as well as the expansion of tools to improve the sampling and analysis of classical molecular dynamics simulations. More recently, this progress embraced also the integration of machine learning in computational chemistry . We expect that soon this plethora of computational tools will have a formidable impact also in the field of colloidal semiconductor nanocrystals.

In this talk I will discuss how to fully capture the power of these computational tools in the chemistry of colloidal nanocrystals, we decided to embed the thermodynamics behind the dissolution/precipitation of nanocrystal-ligands complexes in organic solvents and the crucial process of ligands binding/detachment at the nanocrystal surface into a unique chemical framework. We show that by formalizing this mechanism with a computational bird’s eyes view, helps in deducing the critical factors that govern the stabilization of colloidal dispersions of nanocrystals in an organic solvent as well as the definition of those key parameters that need to be calculated to manipulate surface ligands. This approach has the ultimate goal of engineering surface ligands in-silico anticipating and driving the experiments in the lab.

 

11:45 - 12:05
Discussion
DSSC 1.1
Chair: Marina Freitag
10:45 - 11:05
Abstract not programmed
11:05 - 11:25
1.1-I1
Soman, Suraj
CSIR-NIIST
Serendipity to Breakthroughs: Resurgence of Dye Cells
Soman, Suraj
CSIR-NIIST, IN

Suraj Soman received his PhD in Chemistry from Dublin City University, Ireland in 2012 followed by post-doctoral tenure at Michigan State University, USA. He joined CSIR-NIIST in 2014 and is currently working as Scientist at Chemical Science & Technology Division. His prime research focus is to address basic science issues related to Dye-sensitized Solar Cells (DSCs) for indoor photovoltaics (IPV) & BIPV applications using new generation copper electrolytes. His interdisciplinary research group focuses on establishing structure-function relationships by understanding and advancing the fundamental knowledge through systematic variations of components and interrogating the performance limiting parameters. He played the lead role in setting up India’s first truly indigenous DSC module fabrication line for IPV partnering with industry and was licensed for commercialization in 2019. He is a recipient of CSIR Young Scientist Award (2020), INSA Medal for Young Scientist (2020), Best Emerging Young Scientist Award (2019), BRICS Young Scientist Award (2017), International Strategic Cooperation Award (2015).

Authors
Suraj Soman a
Affiliations
a, Scientist CSIR-National Institute for Interdisciplinary Science & Technology
Abstract

Although extensive research was carried out in the past three decades in almost all aspects of dye-sensitized solar cells/dye cells (DSCs), it failed to penetrate the market, mostly with finding the right applications. In the past 2-3 years, we see a resurgence of dye cells to realize that this is the cheapest known technology best suitable for indoor photovoltaics (IPV). Many factors contributed to this like introducing LEDs and CFL as primary lighting sources replacing conventional incandescent lamps, the emergence of IoT and applications, majority of which sits in closed spaces and require power in µW-mW range. Dye cell research has evolved from traditional molecules, materials, and architectures to address these end-user requirements. Deploying earth-abundant copper as a redox mediator/hole conductor in DSCs is a very promising strategy to achieve higher photovoltage and power conversion efficiencies in full sun and indoor/artificial light conditions. Copper electrolyte offers the flexibility to undertake innovative device engineering concepts in DSCs. I will discuss the benefits of copper electrolyte over the conventional electrolytes (cobalt and iodine) realizing higher PCEs and probe the various deleterious processes taking place in copper devices that provide opportunities to further improve its performance in future.[1][2] Recent updates from our laboratory in the commercialization of dye cell technology for IPVs will also be discussed in short.

11:25 - 11:45
1.1-I2
Deepa, Melepurath
Indian Institute of Technology Hyderabad
Efficient Cost-Effective Designs for High Performance Solar Cells and Photo-supercapacitors
Deepa, Melepurath
Indian Institute of Technology Hyderabad

Melepurath Deepa received her PhD in Applied Chemistry from Delhi University, India in 2004. Thereafter, she worked as a Scientist in the Electronic Materials Division at CSIR-National Physical Laboratory. In November 2009, she joined the Department of Chemistry at the Indian Institute of Technology Hyderabad, and she is currently an Associate Professor and the Head of the Department. Her present research is focused on designing and developing new photoanode and counter electrode architectures for quantum dot solar cells, conducting polymer composites for electrochromic devices and pseudocapacitors, and novel electrode materials for Li-based batteries. She has been a recipient of the CSIR Young Scientist Award in Chemical Sciences (2008), NASI - Young Scientist Platinum Jubilee Award in Chemical Sciences (2010), and the B. M. Birla Science Prize in Chemical Sciences (2013). She has published 125 research articles in peer reviewed SCI journals, contributed to 3 book chapters and filed 4 patents, and has an h-index of 35.

Authors
Melepurath Deepa a, Aparajita Das a, Debanjan Maity a, Ankita Kolay a
Affiliations
a, Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502285, India, IN
Abstract

In recent times, dual function devices capable of performing functions of energy conversion and storage concurrently, over a single platform have captured tremendous scientific interest primarily because they do away with the need to have multiple devices. Co-assembling the two devices into a single one, requires a strategy that allows for efficient charge transfer and transport across the photovoltaic (PV) and the supercapacitor layers while allowing maximum light absorption by the PV part. The application of low cost and easily available natural dyes (like Rose Bengal or Hibiscus etc) for high solar conversion in titania based co-sensitized cells, and the use of novel counter electrode materials like semiconducting metal oxides/chalcogenides like CoTe or MnO2 and their composites with conducting polymers like poly(1-aminoanthraquinone), poly(3,4-ethylenedioxypyrrole) etc, which also double up as the energy storage electrodes, result in highly efficient photo-supercapacitors. Minimizing the transport losses by careful design and implementation of such devices will be discussed. Besides, this, the use of dyes like Zn-porphyrin as sensitizers anchored to imperfect electrodes of silicon nanowires for efficient solar conversion will also demonstrated. 

11:45 - 12:05
Discussion
NanoLight 1.1
Chair: Sascha Feldmann
10:45 - 11:05
1.1-I1
Bakr, Osman
King Abdullah University of Science and Technology (KAUST) - Saudi Arabia
Lead-Free Metal Halide Nanocrystals Combining High Photoluminescence Quantum Yield with Picosecond Radiative Lifetime
Bakr, Osman
King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, SA
Authors
Osman Bakr a
Affiliations
a, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), SA, SA
Abstract

Lead halide compounds, including lead halide perovskite nanocrystals (NCs), have attracted the interest of researchers in optoelectronics and photonics due to their high photoluminescence quantum yields (PLQYs) coupled with relatively short PL lifetimes (on the order of a few nanoseconds). However, lead-free metal halides of high PLQY, including double perovskites and their doped NCs, typically possess  long PL lifetimes (up to microseconds), due to the nature of their excitons, which limits their application space. Here I introduce CsMnBr3 NCs, which are lead-free and combine a high PLQY with an exceptionally short radiative lifetime (on the order of picoseconds). We find that the octahedral coordination of Mn2+ in CsMnBr3 induces a red emission centered at ~643 nm with a PLQY of ~54% and a fast radiative decay rate. Femtosecond transient absorption and transient PL spectroscopies reveal the existence of a low-lying excited state of Mn2+ that relaxes to the ground state within ~600 ps by emitting light at ~643 nm. At greater excitation energies,  higher excited states of Mn2+ relax in the sub-nanosecond timescale to this low-lying excited state. A similarly positioned PL peak with a short picosecond-scale PL lifetime and a PLQY of ~ 6.7% was also detected in bulk CsMnBr3 single crystals – a relatively high quantum yield for a bulk material. Our experimental results and density functional theory modelling show that the crystal structure and the strong coupling among Mn2+ ions govern those luminescence properties of CsMnBr3 NCs and single crystals. These findings pave the way for new lead-free materials that combine high PLQY and ultrafast luminescence.

11:05 - 11:25
1.1-I2
Giovanni, David
Nanyang Technological University (NTU), Singapore
Photophysics of exciton trapping and transport in perovskite quantum dots
Giovanni, David
Nanyang Technological University (NTU), Singapore, SG
Authors
David Giovanni a, Marcello Righetto a, Tze Chien Sum a
Affiliations
a, Nanyang Technological University
Abstract

The outstanding optoelectronic performance of lead halide perovskites leverages their exceptional defect-tolerant and transport properties. As the field starts exploring quantum-confined perovskite systems, the question arises to what extent these traits are still relevant. In this talk, I will discuss the photophysics of these defect-tolerant and transport properties in the case of perovskite nanocrystals (NCs) at two different timescales. At early timescale, we observed the competition between hot-carrier cooling and trapping in MAPbI3 and MAPbBr3 NCs, which were elucidated through optical spectroscopy and phenomenological modeling based on Marcus' theory [1]. Higher excess energies induce faster carrier trapping rates, ascribed to interactions with shallow traps and ligands, turning these into potent defects. Passivating these traps with the introduction of phosphine oxide ligands can help mitigate hot carrier trapping. At the later timescale, we reported long-range exciton diffusion lengths (>1 μm) in MAPbBr3 NCs, corresponding to exciton mobilities up to 10 ± 2 cm2V−1s−1, which is counterintuitively several times higher than the carrier mobility in 3D perovskite films [2]. We discussed the origins of these ultralong exciton diffusions to come from both efficient inter-NC exciton hopping (via Förster energy transfer) and the photon recycling process. The study holds important implications in designing exciton-based perovskite optoelectronic devices.

 

References:

M. Righetto, S. S. Lim, D. Giovanni, J. W. M. Lim, Q. Zhang, S. Ramesh, Y. K. E. Tay & T. C. Sum, Nat. Comm. 11, 2712 (2020).

D. Giovanni, M. Righetto, Q. Zhang, J. W. M. Lim, S. Ramesh & T. C. Sum, Light Sci. Appl. 10, 2 (2021).

11:25 - 11:45
1.1-I3
Ithurria, Sandrine
Ecole Superieure de Physique et de Chimie Industrielles
Halides ligands in II-VI semiconductor nanoplatelets: a new tool for stress release and design of thick nanoplatelets.
Ithurria, Sandrine
Ecole Superieure de Physique et de Chimie Industrielles, FR

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Authors
Sandrine Ithurria a
Affiliations
a, LPEM, Laboratoire de Physique et d’Etude des Matériaux, ESPCI-ParisTech, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS
Abstract

Two-dimensional II-VI semiconductor nanoplatelets (NPLs) present exceptionally narrow optical features due to their thickness defined at the atomic scale. Since thickness drives the band-edge energy, its control is of paramount importance. The native carboxylate ligands can be replaced by halides ligands co-stabilized by amines. This exchange induced a red shift of the optical features. And, the improved surface passivation leads to an increase in the fluorescence quantum efficiency of up to 70% in the case of bromide[1]. These halides ligands can also partially dissolve cadmium chalcogenide NPLs at the edges. The released monomers then recrystallize on the wide top and bottom facets, leading to an increase in NPL thickness. This dissolution/recrystallization method is used to increase NPL thickness to 9 MLs while using 3 ML NPLs as the starting material. When the metal halide precursor is introduced with a chalcogenide precursor on the NPLs, core/shell homo- and heterostructures are achieved. Finally, when an incomplete layer is grown, NPLs with steps are synthesized. These stress-free homostructures are comparable to type I heterostructures, leading to recombination of the exciton in the thicker area of the NPLs. Following the growth of core/crown and core/shell NPLs, it affords a new degree of freedom for the growth of structured NPLs with designed band engineering, which has so far been only achievable for heteromaterial nanostructures[2].

11:45 - 12:05
Discussion
PERIMPED 1.1
Chair: Juan Bisquert
10:45 - 11:05
1.1-I1
Koper, Marc
Leiden University
Stability analysis of electrochemical systems by impedance spectroscopy
Koper, Marc
Leiden University, NL

Marc T.M. Koper is Professor of Surface Chemistry and Catalysis at Leiden University, The Netherlands. He received his PhD degree (1994) from Utrecht University (The Netherlands) in the field of electrochemistry. He was an EU Marie Curie postdoctoral fellow at the University of Ulm (Germany) and a Fellow of Royal Netherlands Academy of Arts and Sciences (KNAW) at Eindhoven University of Technology, before moving to Leiden University in 2005. His main research interests are in fundamental aspects of electrocatalysis, proton-coupled electron transfer, theoretical electrochemistry, and electrochemical surface science.

Authors
Marc Koper a
Affiliations
a, Leiden Institute of Chemistry, Leiden University, Leiden 2300, The Netherlands
Abstract

In this talk, I will summarize the theory of linear stability analysis and show how it relates to impedance spectroscopy data. I will then demonstrate the application of this analysis to a variety of electrochemical systems, ranging from electrocatalysis, corrosion to semiconductor electrochemistry. I will show how the appearance of stationary and oscillatory instabilities (“saddle-node” and “Hopf” bifurcation) can be predicted from impedance spectra. The talk will survey the different electrochemical characteristics that give rise to instabilities. Finally, I will discuss how these instabilities can give rise to further non-linear instabilities such as homoclinic bifurcations and transitions to deterministic chaos. Such behavior cannot be predicted from impedance data.

11:05 - 11:25
1.1-I2
Klotz, Dino
Kyushu University
Towards a General Recipe for the Use of Impedance Spectroscopy to Characterise Perovskite Solar Cells
Klotz, Dino
Kyushu University, JP
Authors
Dino Klotz a, Elizabeth von Hauff b
Affiliations
a, Kyushu University, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Japan, 744 Motooka, Nishi, Fukuoka, JP
b, Vrije Universiteit Amsterdam, Department of Physics and Astronomy, Faculty of Science, NL
Abstract

In essence, impedance spectroscopy (IS) could turn out to be the most suitable technique for in operando characterisation of full perovskite solar cell (PSC) devices under light operation. IS can serve for a range of purposes: to identify reaction steps and losses, to compare different cells and configurations, and to find the performance and efficiency limiting factors.

However, there is no established standard recipe yet. In part, that is because PSC have long struggled with stability issues such that it was not possible to conduct the often lengthy IS measurements in a consistent manner. As this has been changing rapidly in the last couple of years, it is now time to have a look at those recent results and to establish standardized testing procedures and models.

In this talk, we will be introducing some basic principles of IS and point out how they are particularly relevant for PSC. Further, we will present some pitfalls and particularities and practical guidelines for the consistent use of IS.

One particularity that will receive special attention will be the low frequency hooks frequently encountered in IS measurements on PSC in the mid- and low-frequency regions. This feature has been called: (low-frequency) inductive loop, curl-back or negative loop and is found for example in Lithium Ion batteries, proton exchange fuel cells (PEFC), organic light emitting diodes (OLED), perovskite solar cells (PSC), thin film model electrodes, and in the field of corrosion. In this talk, measurement examples will be presented that exhibit such hooks, caused by both measurement artifacts and as consistent feature of the PSC. On that basis, it will be discussed how to distinguish features from artifacts and why such hooks may occur.

In sum, this talk presents an update of the recent perception of IS and is intended to pave the way towards a unified theory on measurement, analysis and interpretation of IS on PSC in order to work towards a consistent and conclusive in operando analysis and diagnosis of PSC.

11:25 - 11:45
1.1-I3
Knapp, Evelyne
ZHAW
Modeling Perovskite Solar Cells from Lab-to-Fab
Knapp, Evelyne
ZHAW, CH

Dr. Evelyne Knapp is a research associate at the Institute of Computational Physics at the Zurich University of Applied Sciences in Winterthur, Switzerland. She holds a Diploma and Ph.D. degree in Computational Science and Engineering from ETH Zurich.

Authors
Evelyne Knapp a, Martin Neukom b, Ennio Comi a, Mattia Battaglia a, Christoph Kirsch a, Beat Ruhstaller a, b
Affiliations
a, Institute of Computational Physics, Zurich University of Applied Sciences (ZHAW), 8401 Winterthur (Switzerland)
b, Fluxim AG, CH, Katharina-Sulzer-Platz, 2, Winterthur, CH
Abstract

Modelling of perovskite solar cells and related semiconductor devices is key for a thorough understanding of the underlying physical processes. In the first part of this contribution, a comprehensive one-dimensional drift-diffusion model is presented. The coupled opto-electrical model for a multi-layer methylammonium lead iodide (MAPI) perovskite device including mobile ionic charge carriers, charge trapping, Shockley-Read-Hall (SRH) recombination and doped transport layers is validated with multiple different experiments. We therefore find a material and device parameter set that optimally describes the DC, AC and transient measurements [1]. Exploring the parameter space for an optimal parameter set for device description is a challenging task [1,2] that we recently tackled with the aid of machine learning.

In the second part of the talk, we discuss the modelling of large-area devices and present a 1D+2D approach [3] that is extended to the frequency domain for the impedance simulation of perovskite devices. To validate the assumption of the underlying cell and material parameters we compare the impedance and the steady-state simulations with impedance spectroscopy measurements and electroluminescence (EL) images. The impedance spectra exhibit distinct features related to the sheet resistance, homogeniety and size of the large-area solar cell. Further, we also solve the heat transport equation and compare the results with a small-signal DLIT (dark lock-in thermography) technique.

The simulation of large-area devices is helpful in the cell upscaling and optimization process. Furthermore, EL and DLIT images provide us with valuable spatial information that complements signals acquired in traditional 2-terminal electrical measurements.

 

 

11:45 - 12:05
Discussion
SOLFUL 1.1
Chair not set
10:45 - 11:05
1.1-I1
Pazke, Greta Ricarda
University of Zurich
3d Transition Metal Centers for Single Atom- and Ultra-Thin Coordination Polymer-Based Electrocatalysts
Pazke, Greta Ricarda
University of Zurich, CH
Authors
Greta Ricarda Pazke a, Yonggui Zhao a, Wenchao Wan a, Carlos A. Triana a, Jingguo Li a, Marcella Iannuzzi a, Rolf Erni b, Christopher S. Allen c
Affiliations
a, University of Zurich, Department of Chemistry, Winterthurerstrasse, 190, Zürich, CH
b, EMPA - Swiss Federal Laboratories for Materials Science and Technology, Überland Strasse, 129, Dübendorf, CH
c, Diamond Light Source, Didcot OX11 0DE, UK.
Abstract

The development of economic and efficient catalysts for the oxygen evolution reaction (OER) is a crucial bottleneck for generating clean hydrogen fuel through water splitting. The targeted development of OER catalysts has become a "melting pot" for diverse strategies in catalysis.[1] Elucidating the reaction mechanisms and structure-function correlations of low-cost 3d transition metal centers in various matrices is crucial to enhance their performance and robustness. To this end, single atom catalysts (SACs) keep attracting intense research interest as model systems, and we recently introduced a soft-landing molecular strategy to tailor metal phthalocyanines (MPc, M = Ni, Co, Fe) on graphene oxide (GO) layers.[2] This facile access to highly defined SACs enabled us to elucidate key performance parameters of their promising dual OER and oxygen reduction reaction (ORR) activity. Both processes benefited considerably from pi-pi conjugation of MPc-SACs with the GO sheets via electronic channels. Their ORR activity trend (FePc-GO > CoPc-GO > NiPc-GO) was mainly related to the strongest bonding affinity of Fe(III) centers to O2, as evident from DFT results and operando XAS monitoring. Interestingly, the opposite OER trend with NiPc-GO exhibiting the highest activity was clearly linked to a wider range of alternative N/C-based reaction pathways. Our XAS studies offered unprecedented experimental insight into SACs under operational OER conditions as a basis for their informed performance enhancement. We then proceeded to investigate the high-performance interplay of Ni and Fe centers in OER catalysts based on ultra-thin coordination polymers (CPs).[3] The manifold advantages of CP assemblies, e.g. enhanced dispersion of metal sites and surface areas, remain to be fully explored for heterogeneous electrocatalysis. To this end, we designed a series of ultra-thin Ni10-xFex-CPs with a facile coprecipitation-reduction protocol that gave access to significant extents of structural deficiencies. The resulting reduced, sub-2 nm R-NiFe-CP nanosheets displayed competitive and durable OER performance at a low overpotential of 225 mV (at 10 mA cm-2) over 120 h (best for R-Ni8Fe2-CPs). Based on comprehensive analyses including XAS measurements, DFT results and mass diffusion theory, we linked the high OER activity to the strong influence of synergistic effects from structural deficiencies. Furthermore, our mechanistic investigations pointed to a favorable decoupled proton-electron transfer pathway taking place in the R-NiFe-CP nanosheets. The dual bridging Ni-O-Fe units were identified as catalytically active sites with the RDS depending on their asdorption of HO-. This work opened up convenient options for the tuning and scale-up of economic CP-based electrocatalysts.

11:05 - 11:25
1.1-I2
Rossmeisl, Jan
University of Copenhagen
Electro-Catalysis on High Entropy Alloys
Rossmeisl, Jan
University of Copenhagen, DK
Jan Rossmeisl is Professor of theoretical chemistry at Department of Chemistry and the Nano-Science center at Copenhagen University. Before joining University of Copenhagen in April 2015, Jan was an Associate Professor and group leader for the theoretical catalysis group at Department of Physics at the Technical University of Denmark Jan holds master’s (2000) and Ph.D (2004) degrees in physics from the Technical University of Denmark. Since 2007 supervisor of more than 20 Ph.D and Post docs. Coauthor of more than 110 publications in peer reviewed journals, co-inventor of 4 patents and co-founder of two startup Companies. Research interests includes: electrocatalysis, energy conversion, atomic scale simulations, rational interface design for catalysis.
Authors
Jan Rossmeisl a
Affiliations
a, University of Copenhagen, Department of Chemistry
Abstract

The chemical industry should in the future be based on renewable energy. Therefore, material development for environmentally friendly, electrocatalytic production of valuable chemicals is needed.

Chemicals could be produced using safe, cheap, more environmentally friendly and more abundant reactants than today. The products could be provided on demand at the place where they are needed, reducing expensive and hazardous transport of chemicals. However, stable, efficient and selective catalysts have to be discovered. This requires insight into the surface chemistry at the atomic scale.

The challenge of discovering new catalyst materials is twofold: Firstly, the properties or descriptors of the wanted catalyst have to be identified. Secondly, real materials with the wanted properties should be found.

I will give examples of determining descriptors for different reactions and a method for identify promising catalyst materials based on high entropy alloy, which is a new class of materials with the promise to change the way we discover interesting catalyst materials.

11:25 - 11:45
1.1-I3
Roldan Cuenya, Beatriz
Fritz Haber Institute of the Max Planck Society
Dynamic CO2 electroreduction catalysts
Roldan Cuenya, Beatriz
Fritz Haber Institute of the Max Planck Society, DE

Since 2017 Beatriz Roldan Cuenya has been a Director at the Fritz Haber Institute of the Max Planck Society in Berlin (Germany). There she heads the Department of Interface Science. She moved from the Ruhr-University Bochum (Germany), where she became a professor of Physics in 2013. Prior to that, Beatriz Roldan Cuenya was a professor of Physics at University of Central Florida (USA).

She carried out her postdoctoral research in the Department of Chemical Engineering at the University of California Santa Barbara (2001-2003). Prof. Roldan obtained her PhD in Physics from the University of Duisburg-Essen (Germany) summa cum laude in 2001. She completed her M.S./B.S. in Physics with a minor in Materials Science at the University of Oviedo, Spain in 1998. During her academic career Prof. Roldan received an Early CAREER Award from the US National Science Foundation (2005) and the international Peter Mark Memorial award from the American Vacuum Society (2009). She is the author of more than 110 peer-reviewed publications and 3 book chapters and has given over 100 invited talks. She presently serves as Associate Editor of ACS Catalysis, in the editorial advisory board of the Surface Science journal and in the Advisory Committee of the Office of Basic Energy Sciences of the US Department of Energy.

Prof. Roldan’s research program explores the novel physical and chemical properties of size and shape-selected nanostructured materials, with emphasis on advancing the field of nanocatalysis through in situ and operando characterization of catalysts at work.

Authors
Beatriz Roldan Cuenya a
Affiliations
a, Department of Interface Science, Fritz-Haber-Institute of the Max Planck Society, Berlin
Abstract

In the quest for developing a sustainable energy economy, the electrochemical reduction of carbon dioxide (CO2RR) into value-added chemicals and fuels offers the potential to close the anthropogenic carbon cycle and store renewable energy (wind, solar, hydro) into chemical bonds. It is therefore of particular interest to develop efficient and selective electrocatalysts, which reduce the reaction overpotential and steer the reaction toward hydrocarbons and multicarbon oxygenates (C2+ products). Nonetheless, in order to tailor the chemical reactivity of CO2RR nanocatalysts at the atomic level, fundamental understanding of their physical and chemical properties under reaction conditions must be obtained. To fulfill this challenging aim, a synergistic experimental approach taking advantage of a variety of cutting-edge methods (EC-AFM, EC-TEM, TPD, XPS, XAFS, MS/GC) has been undertaken.

This talk will provide new insights into the CO2RR, with special focus on: (i) the design of size-and shape-controlled catalytically active NPs (Cu, Cu-Zn, Cu-Ag), and (ii) the correlations between the dynamically evolving structure and composition of the electrocatalysts under operando reaction conditions, including pulse electrolysis treatments. The results are expected to open up new routes for the reutilization of CO2 through its direct conversion into valuable chemicals and fuels such as ethylene and ethanol.

 

11:45 - 12:05
Discussion
TINPERO 1.1
Chair not set
10:45 - 11:05
1.1-I1
Hayase, Shuzi
Solar cells consisting of tin perovskite as light harvesting layer
Hayase, Shuzi
Authors
Shuzi Hayase a
Affiliations
a, The University of Electro-Communications
Abstract

Recently, Sn perovskite solar cells (Sn PVK PV) are attracting attention because this is one of Pb free perovskites and has best band gap from the view point of Shockley-Queisser limit. However, the efficiency was still lower than that of Pb perovskite solar cells. Recently, the Sn PVK PVs with efficiency higher than 10% have been reported from several research groups. Pb perovskite has defect tolerance properties because these lattice defects do not create deep carrier traps. Filippo and his coworkers have reported that some of defects in Sn perovskite solar cells make deep traps[1,2]. The crystal defects include the presence of Sn4+, Sn2+ defect, I- defect, the presence of Sn0, the interstitial I- and so on. The presence of Sn4+ increases carrier densities and causes charge recombination. Many reports for enhancing these efficiencies are on adding reducing agencies in the perovskite precursor solutions. One of our trials is to add Ge2+ ion in the precursor solution. After 5 % of Ge ion doping, the efficiency was enhanced from about 5 % to 7.9 %. Ge ion passivates the grain boundary and hetero-interfaces, and decreases the carrier concentrations associated with Sn2+ defect and Sn4+. The Ge ion in the hereto-interface was partially oxidized to give GexOy protecting the perovskite layer from air and moisture. Partial displacement of A site with ethyl ammonium cation with optimized bulkiness makes the band energy level deeper and gives less lattice disordering. It has been reported that the former makes the energy level of Sn2+ defect shallower[1,2]. In addition, the latter gave carrier lifetime longer and decreased the Sn4+ carrier concentration. The third item is the surface passivation with diaminoethane solution. After the passivation, the efficiency was enhanced from 7.3% to 10.05%, accompanied by Voc enhancement from 0.49 V to 0.63 V. The diaminoethane passivation decreased the Sn4+ concentration, and probably passivates uncoordinated Sn2+ site (defect of I- ion). Finally, Sn-perovskite solar cells were fabricated by doping Ge2+ ion, passivating the grain boundary with diaminoethane, and replacing A site with ethyl ammonium cation. 13 % efficiency with high Voc of 0.84 V was observed[3]. In addition, SnPb PVK PV with 23.3 % efficiency will be reported.

11:05 - 11:25
1.1-I2
Wakamiya, Atsushi
Kyoto University, Japan
Highly Purified Tin Perovskite Materials for Efficient Solar Cells
Wakamiya, Atsushi
Kyoto University, Japan, JP
2010- Associate Professor (Kyoto University) 2003–2010 Assistant Professor (Nagoya University) 2003 Ph D. Kyoto Univeristy 2000 Visiting Student (Boston College, USA) 1998 B Kyoto Univeristy
Authors
Atsushi Wakamiya a
Affiliations
a, Institute for Cemical Research, Kyoto University
Abstract

  The toxicity of lead perovskite hampers the commercialization of perovskite-based photovoltaics. While tin perovskite has attracted attention as a promising alternative, the improvement of the solar cell performance of tin-based perovskite still remains as challenging issue. Among several factors responsible for the poor efficiency, we will focus on the facile oxidation of tin(II) to tin(IV), as well the difficulties in suppressing structural defects in the perovskite film.

  Based on highly-purified precursor materials and improved fabrication methods, we have improved the performance of tin-based perovskite solar cells [1]. In this presentation, we will introduce highly purified precursor materials for tin perovskite [2], fabrication methods for uniform tin-perovskite films [3], and scavenging techniques for suppressing tin(IV) contamination in the films [4].

11:25 - 11:45
1.1-I3
Ning, Zhijun
ShanghaiTech University
Low dimensional tin perovskite solar cells
Ning, Zhijun
ShanghaiTech University, CN
Authors
Zhijun Ning a
Affiliations
a, ShanghaiTech University, 100 Haike Road, Shanghai, 201210, CN
Abstract

The development of high performance lead free perovskite solar cells (PSCs) is important to address the environmental concern. In recent years, tin perovskite solar cell (TPSCs) is developing quickly and emerging as a promising candidate for high efficiency lead free PSCs. In this presentation, I will summarize our recent work about low dimensional tin perovskite solar cells, such as regulating crystal growth kinetic to build nanostructure, as well as device structural engineering to reduce interface carriers recombination. In the end, the challenges for TPSCs and potential strategies toward high efficiency TPSCs will be discussed. The unique properties of tin perovskites that distinguish them from lead perovskites, including electronic structure, band structure, chemical properties will be highlighted.

 

[1] Nat. Commun.,2020, 11, 1245.

[2] Joule, 2018. 2, 2732-2743.

[3] J. Am. Chem. Soc., 2017, 139, 6693–6699.

[4] Energy Environ. Mater., 2020, doi:10.1002/eem2.12075.

[5] J. Phys. D: Appl. Phys., 2020, 53, 41400.

[6] Appl. Phys. Lett. 2020, 117, 060502.

[7] Acta Phys. -Chim. Sin. 2021, 37 (X), 2007090.

11:45 - 12:05
Discussion
12:05 - 14:00
CHEMNC Break
12:05 - 15:15
DSSC Break
NanoLight 1.2
Chair: Sascha Feldmann
12:05 - 12:15
1.2-T1
Schröder, Vincent
Helmholtz-Zentrum Berlin, HySPRINT Innovation Lab, Young Investigator Group Hybrid Materials Formation and Scaling, Germany
Inkjet-Printed Perovskite LEDs Using 'Salty' PEDOT:PSS
Schröder, Vincent
Helmholtz-Zentrum Berlin, HySPRINT Innovation Lab, Young Investigator Group Hybrid Materials Formation and Scaling, Germany, DE
Authors
Vincent Schröder a, d, Felix Hermerschmidt a, Florian Mathies b, Carolin Rehermann b, Nicolas Zorn Morales a, Eva Unger b, c, Emil List-Kratochvil a, d
Affiliations
a, Humboldt‐Universität zu Berlin, Institut für Physik, Institut für Chemie, IRIS Adlershof, Germany, DE
b, Helmholtz-Zentrum Berlin, HySPRINT Innovation Lab, Young Investigator Group Hybrid Materials Formation and Scaling, Germany, Kekulestraße, 5, Berlin, DE
c, Lund University, Department of Chemical Physics and NanoLund, Sweden, Lund, SE
d, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, Berlin, DE
Abstract

Metal halide perovskites are not only a high performing solar cell material but are also under investigation as emitter material for light emitting diodes. A major advantage over established inorganic materials is the solution processability of perovskites, which would enable fast and cheap large-area and high-throughput production. But while metal halide perovskite solar cells are already moving towards commercialisation, the fabrication of perovskite-based light emitting diodes has not yet moved beyond laboratory-based methods, such as spin coating. 
We present the first perovskite-based light emitting diodes with an inkjet-printed perovskite layer. We use a composite of methylammonium lead bromide (MAPbBr3) and polyethylene glycol (PEG) to achieve a suitable morphology for device application without spin-coating based techniques such as the anti-solvent drip.
Furthermore, we investigated the effect of potassium chloride (KCl) added during deposition of the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) contact layer underneath the perovskite. Agglomeration of KCl at the layer surface provided a template for the crystallization of perovskite while having only a minor effect on the electrical properties of PEDOT:PSS. Devices with an inkjet-printed MAPbBr3:PEG composite layer exhibit a 30-fold increase in brightness to a maximum of 4.000 cd/m², at the same operating voltage as the reference device with pure PEDOT:PSS.[1]

12:15 - 12:25
1.2-T2
Sandberg, Oskar J.
The Effect of Radiative Mid-Gap Trap States in Organic Photovoltaic Devices
Sandberg, Oskar J.
Authors
Oskar J. Sandberg a, Nasim Zarrabi a, Stefan Zeiske a, Wei Li a, Drew B. Riley a, Paul Meredith a, Ardalan Armin a
Affiliations
a, Sustainable Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, UK, Singleton Park, Swansea, SA2 8PP Wales, GB
Abstract

The photocurrent and open-circuit voltage (VOC) generated by a solar cell is predominantly defined by the bandgap of the used semiconductor. For donor-acceptor organic solar cells it has been shown that intermolecular charge transfer (CT) states define the effective bandgap energy and, thereby, determine the radiative limit of the VOC via detailed balance and the principle of reciprocity between emission and absorption [1]. In this work, we employ ultrasensitive photocurrent measurements and detect sub-gap states with energies below the CT states in a significant number of donor-acceptor blends [2]. However, taking these sub-gap states into account and using the principle of reciprocity resulted in non-physical radiative limits for the VOC. We explain this deviation by providing evidence that the observed low-energy sub-gap states are associated with radiative mid-gap trap states, generating photocurrent via an optical release process which up-converts these states to CT states. To account for the radiative mid-gap states, we implement a two-diode model which accurately describes the dark current and the VOC, but also explains the long-debated ideality factor in organic solar cells. These findings provide important insights for our current understanding of next-generation photovoltaic devices such as organic solar cells and photodiodes.

12:25 - 12:35
1.2-T3
Kaiser, Christina
Department of Physics, Swansea University, UK
A Universal Urbach Rule for Disordered Organic Semiconductors
Kaiser, Christina
Department of Physics, Swansea University, UK, GB
Authors
Christina Kaiser a, Oskar J. Sandberg a, Nasim Zarrabi a, Wei Li a, Paul Meredith a, Ardalan Armin a
Affiliations
a, Sustainable Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, UK, Singleton Park, Swansea, SA2 8PP Wales, GB
Abstract

In crystalline semiconductors, the sharpness of the absorption spectrum onset is characterized by temperature-dependent Urbach energies.1 These energies quantify the static, structural disorder2 causing localized exponential tail states, and the dynamic disorder due to electron-phonon scattering3. The applicability of this exponential-tail model to molecular and amorphous solids has long been debated.4 Nonetheless, exponential fittings are routinely applied to the analysis of the sub-gap absorption of organic semiconductors and their blends alongside Gaussian-like spectral line-shapes predicted by non-adiabatic Marcus theory. Herein, we elucidate the sub-gap spectral line-shapes of organic semiconductors and their blends by temperature-dependent quantum efficiency measurements.5 We show that the Urbach energy associated with singlet excitons universally equals the thermal energy regardless of static disorder.6 We show that these observations are consistent with absorption spectra obtained from convolution of Gaussian density of excitonic states weighted by a Boltzmann factor taking into account optical interference effects7. A generalized Marcus transfer model is presented that explains the absorption spectral line-shape of disordered molecular matrices and simple approach given to determine excitonic disorder energy. Our findings elaborate the true meaning of dynamic Urbach energy in molecular solids and provide means for relating photophysics to static disorder, crucial for optimizing molecular electronic devices.

12:35 - 13:05
Discussion
PERIMPED 1.2
Chair: Dino Klotz
12:05 - 12:15
1.2-T1
Guerrero, Antonio
Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain
Negative capacitance effects in perovskite memristor dynamics
Guerrero, Antonio
Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, ES

Antonio Guerrero is a materials science chemist currently contracted as a Ramón y Cajal Fellow at the Institute of Advanced Materials (Jaume I University, Spain).  Antonio completed a Ph.D. in Organometallic Chemistry (University of East Anglia, UK) industrially funded by Bayer CA focused on the design of new catalysts for the production of butyl rubber. Subsequently, Antonio worked during 4 years at the company Cambridge Display Technology where he developed some of the state of the art semiconducting materials for Organic Light Emitting Diodes (OLEDs). In 2010 Antonio Guerrero joined the group of Prof. Juan Bisquert at the University Jaume I where he learnt the insights of impedance spectroscopy to understand the operation mechanism of several electronic devices. Over the last few years, his work has been focused in three different lines of research: 1-Perovskite Materials for photovoltaic applications, 2-Organic Photovoltaics and 3- Photoelectrochemical Cells.

Authors
Antonio Guerrero a, Cedric Gonzales a, Juan Bisquert a
Affiliations
a, Institute of Advanced Materials (INAM), Universitat Jaume I, 12006 Castelló, Spain
Abstract

Negative capacitance and loops have been observed during the analysis of Impedance Spectroscopy results in perovskite solar cells.1-4 The origin of these features seems to be related to the dynamic interaction of migrating ions with external interfaces and play a role in memristor switching between high and low resistance states. Here we present the dynamic state transition in a 2D Ruddlesden-Popper perovskite-based memristor device, measured via impedance spectroscopy.5 The spectral evolution of the transition exhibits a significant transformation of the low frequency arc to a negative capacitance arc, further decreasing the device resistance. The capacitance-frequency evolution of the device indicates that the appearance of the negative capacitance is intimately related to a slow kinetic phenomenon due to ionic migration and redistribution occurring at the perovskite/metal contact interface. In contrast, no negative capacitance arc is observed during the state transition of a memristor device where the contact is passivated by an undoped Spiro-OMeTAD interfacial layer. The switching mechanisms are entirely different, one due to interface transformation and the other one to filamentary formation.

12:15 - 12:25
1.2-T2
Pockett, Adam
SPECIFIC, Swansea University
The High Frequency IMPS/IMVS Response of Perovskite Solar Cells
Pockett, Adam
SPECIFIC, Swansea University, GB
Authors
Adam Pockett a, Matthew Carnie a
Affiliations
a, SPECIFIC – Swansea University, Materials Research Centre, College of Engineering, UK, Bay Campus, Swansea, SA1 8EN,, SWANSEA, GB
Abstract

The complete interpretation of small perturbation frequency domain measurements on perovskite solar cells has proven to be challenging. This is particularly true in the case of intensity modulated photocurrent/photovoltage (IMPS/IMVS) measurements, in which the high frequency response is obscured by instrument limitations. In this work, we demonstrate the use of a custom-built system capable of accurately resolving the high frequency response of a range of perovskite devices. We are able to construct the time dependent IMPS/IMVS response of these devices during their initial response to illumination. This reveals significant negative photocurrent/photovoltage signals at high frequency during the rise to steady state, in keeping with observations made from comparable transient measurements. These techniques allow the underlying interfacial recombination and ion migration processes to be assessed, which are not always evident using steady-state measurements. The ability to study and mitigate against these processes will be vital in optimizing the real-world operation of devices.

12:25 - 12:35
1.2-T3
Bag, Monojit
Indian Institute of Technology Roorkee, India
Photo-electrochemical Impedance Spectroscopy in Hybrid Perovskites: Unveiling the Curious Case of Ion Migration
Bag, Monojit
Indian Institute of Technology Roorkee, India, IN

Dr. Bag is currently an assistant professor of Department of Physics and an adjunct faculty of Centre of Nanotechnology at Indian Institute of Technology Roorkee, India. He got his Bachelor degree in Electrical Engineering from Jadavpur University and Master degree in Physics from University of Pune in 2003 and 2006 respectively. After completing PhD from Jawaharlal Nehru Centre for Advanced Scientific Research, India in the field of Material Science in 2011 he did few years of postdoctoral work at University of Massachusetts Amherst, USA and at Lund University, Sweden before joining to IIT Roorkee in 2016.

Dr. Bag has worked on multi-disciplinary projects during PhD and postdoctoral works with multiple research groups. His expertise varies from device fabrication to various characterization including theoretical modelling and simulations. He has been working in the field of organic electronics for last fourteen years and hybrid perovskite-based materials for energy harvesting for last six years. His current research laboratory known as Advanced Research in Electrochemical Impedance Spectroscopy (AREIS) at IIT Roorkee is focusing on the impedance spectroscopy measurement of various kinds of optoelectronic materials along with the fabrication and optimization of large area thin film based solar cells and LEDs.

Authors
Monojit Bag a, Ramesh Kumar a, Priya Srivastava a
Affiliations
a, Department of Physics, Indian Institute of Technology Roorkee, IN
Abstract

Ion migration in hybrid perovskite materials is one of the most debated topics of research in recent years. Despite tremendous progress in optoelectronic device application, perovskites are lacking in terms of their environmental stability. One of the major causes of degradation is ion migration under operating condition. It is to be believed that the A-site cation migration is photo as well as thermally activated while the X-site halide ions can migrate even in dark as well as at low/room temperature. The interaction between A-site cations to that of X-site halide ion are important parameters for determining the ac ionic conductivity in perovskite-based devices. In this talk I will also deliberate on the fact that the device geometry plays a crucial role on the ac ionic conductivity. Photo-electrochemical Impedance Spectroscopy (PEIS) has been used to study the ac ionic conductivity in solid state device and perovskite/electrolyte-based device to understand the electronic-ionic coupling in ac ionic conductivity. A super-linear power law in ac ionic conductivity can also be observed in mixed cation mixed halide devices at room temperature.

12:35 - 13:05
Discussion
SOLFUL 1.2
Chair not set
12:05 - 12:15
1.2-T1
Andrei, Virgil
University of Cambridge - UK
Rational Design of Photoelectrochemical Perovskite-BiVO4 Tandem Devices for Selective Syngas Production
Andrei, Virgil
University of Cambridge - UK, GB
Authors
Virgil Andrei a, b, Geani M. Ucoski a, Motiar Rahaman a, Chanon Pornrungroj a, Esther Edwardes Moore a, Bertrand Reuillard a, Qian Wang a, Demetra S. Achilleos a, Robert A. Jagt c, Chawit Uswachoke d, Hannah J. Joyce d, Robert L. Z. Hoye b, c, Judith L. MacManus-Driscoll c, Richard H. Friend b, Erwin Reisner a
Affiliations
a, Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
b, Optoelectronics Group, University of Cambridge, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
c, Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Rd, Cambridge CB3 0FS, United Kingdom.
d, Electronic and Photonic Nanodevices, Department of Engineering, University of Cambridge, Electrical Engineering Building, 9 J J Thomson Avenue, Cambridge CB3 0FA, United Kingdom.
Abstract

Metal halide perovskites have recently emerged as promising alternatives to commonly employed light absorbers for solar fuel synthesis.[1,2] These semiconductors enabled photoelectrochemical (PEC) perovskite-BiVO4 tandem devices which can perform unassisted water splitting,[3,4,6] as well as the more challenging CO2 reduction to syngas.[5,7] While the bare perovskite light absorber is rapidly degraded by moisture, recent developments in the device structure have led to substantial advances in the device stability, from seconds to days.

In this contribution, we give an overview of the latest progress from the field of perovskite PEC devices, introducing design principles to improve their performance and reliability. For this purpose, we will discuss the role of charge selective layers in increasing the device photocurrent and photovoltage, by fine-tuning the band alignment and enabling efficient charge separation. A further beneficial effect of hydrophobicity is revealed by comparing devices with different hole transport layers (HTLs). A threefold increase in the lifetime of perovskite photocathodes is obtained by replacing a hydrophilic PEDOT:PSS HTL with an inorganic NiOx HTL.[3] A further leap in stability up to 96 h can be demonstrated by introducing a hydrophobic PTAA HTL, which acts as an additional barrier to lateral moisture infiltration while further increasing the onset potential for H2 evolution to approximately 1.0 V vs. RHE.[6]

On the manufacturing side, we will provide new insights into how appropriate encapsulation techniques can extend the device lifetime to a few days under operation in aqueous media.[3,5] Many prototypes rely on low melting alloys as encapsulants, however the demand on rare elements can be detrimental for the overall cost and scalability of the tandems, whereas metals can suffer from chemical corrosion. To avoid these drawbacks, we introduce graphite epoxy paste as a conductive, hydrophobic encapsulant.[6,8] This abundant, metal-free composite can reduce the device cost[6] while enabling a more facile integration of perovskite devices with inorganic,[6,7] molecular[5] and bio-catalysts.[4] The combined advantages of these approaches are demonstrated in a perovskite-BiVO4 tandem configuration, leading to selective unassisted CO2 reduction to syngas.[7]

12:15 - 12:25
1.2-T2
Holmes-Gentle, Isaac
Ecole Polytechnique Federale de Lausanne (EPFL)
Developing a unifying device classification system for a solar fuel database
Holmes-Gentle, Isaac
Ecole Polytechnique Federale de Lausanne (EPFL), CH
Authors
Isaac Holmes-Gentle a, Franky Bedoya-Lora b, Fatwa Abdi c, Anna Hankin d, Roel van de Krol c, Sophia Haussener a
Affiliations
a, Laboratory of Renewable Energy Science and Engineering, Institute of Mechanical Engineering, École Polytechnique Fédérale de Lausanne, Switzerland
b, Universidad de Antioquia, Medellín, Colombia
c, Institute for Solar Fuels, Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH, Berlin, Germany
d, Electrochemical Systems Laboratory, Imperial College London, United Kingdom
Abstract

The challenge of any classification system is it must possess the ability to capture complexity whilst remaining comprehensible and useful. In the field of solar fuels, there have been a number of classification systems and taxonomies proposed [1,2] which whilst are undeniably useful to the community, lack the complexity required for a structured database of solar fuel devices. We therefore propose a new abstraction of the solar fuel device into its constituent subcomponents. Attributes, such as material, area or bandgap etc., can then assigned to each subcomponent, and performance metrics assigned to the device (e.g. efficiency, stability etc.). The key insight is that a versatile classification system must record the path of the photons and charge through the subcomponents. Therefore, the relationship between subcomponents are specified with two directed graphs (representing the optical and electronic configuration). This permits the facile creation of multiple classification systems, including those already used in the field, from the structured data framework.

The structured data framework developed here will facilitate the ultimate goal of this project, the systematic creation of a database of solar fuel with sufficient detail to allow high quality meta-studies. This will uncover new insights, identify knowledge gaps and highlight relevant challenges whilst assisting in avoiding research duplication. We will present our preliminary review of photo-electrochemical water splitting devices demonstrating the utility of the proposed device classification system. Finally, the most commonly absent critical data/parameters from the reviewed literature will be quantified (e.g. photo-active areas, stability measurements etc.) and consequently reporting guidelines will be discussed.

12:25 - 12:35
1.2-T3
Peugeot, Adèle
College de France
Benchmarking of Oxygen Evolution Catalysts on Porous Nickel Supports
Peugeot, Adèle
College de France, FR
Authors
Adèle Peugeot a, Charles Creissen a, Moritz Schreiber b, Dilan Karapinar a, Ngoc Huan Tran a, Marc Fontecave a
Affiliations
a, Laboratoire de Chimie des Processus Biologiques, UMR CNRS 8229, Collège de France-CNRS-Sorbonne Université, PSL Research University, FR
b, Total Research & Technology, Refining and Chemical, Division CO2 conversion, Feluy, 7181 Seneffe, Belgium
Abstract

Active and inexpensive oxygen evolution reaction (OER) electrocatalysts are required for energy efficient electrolysis applications. Objective comparison between OER catalysts has been blurred by the use of different supports and methods to evaluate performance. We selected nine highly active transition-metal-based catalysts and describe their synthesis using a porous nickel foam and a new Ni-based dendritic material as the supports. We designed a standardised protocol to characterise and compare the catalysts in terms of structure, activity, and stability. We highlight the most active anode materials and provide an easy way to increase the geometric current density of a catalyst by tuning the porosity of its support.

12:35 - 13:05
Discussion
TINPERO 1.2
Chair not set
12:05 - 12:15
1.2-T1
Xi, Jun
University of Groningen, The Netherlands
Highly Crystalline and Stable 3D Lead-Tin Perovskites from Scalable Ruddlesden-Popper Perovskites Templates Driven Growth
Xi, Jun
University of Groningen, The Netherlands, NL
Authors
Jun Xi a, Maria Loi a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Abstract

3D lead-tin halide perovskites with narrow bandgaps are expected to approach the theoretical maximum efficiency of single junction solar cells and to have an important role in tandem solar cells. However, most of the related fabrication methods are limited to laboratory scale and not easily scalable methods, contradicting the hope towards a future scalable industrial production.

To this end, here I will show a scalable method for the deposition of narrow bandgap metal halide perovskites. The method is based on the deposition by doctor-blade coating of a Ruddlesden-Popper (RP) 2D lead-tin perovskites as template, which is subsequently dipped into a halide salt solution to in-situ grow a 3D perovskites. The ordered template driven growth of the 3D lead-tin perovskite has a stoichiometric composition and a preferred out-of-plane orientation, in stark contrast with the disordered low crystalline features of spin-coated films. Importantly, the low surface/volume ratio of the fabricated single-crystal-like domains contributes to the improved stability of the films. We further demonstrate that these highly crystalline lead-tin films hold a great potential for device application.

12:15 - 12:25
1.2-T2
Aldamasy, Mahmoud
Solvents for processing stable tin halide perovskites
Aldamasy, Mahmoud
Authors
Mahmoud Aldamasy a, c, Diego Di Girolamo b, Jorge Pascual a, Zafar Iqbal a, Guixiang Li a, Eros Radicchi d, e, Meng Li a, Silver-Hamill Turren-Cruz a, Giuseppe Nasti b, André Dallmann f, Filippo De Angelis d, e, g, Antonio Abate a, b
Affiliations
a, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
b, Department of Chemical, Materials and Production Engineering. University of Naples Federico II. Naples, pzz.le Vincenzo Tecchio 80, 80125, Naples Italy
c, Egyptian Petroleum Research Institute, Nasr City, P.O. 11727, Cairo, Egypt
d, Department of Chemistry, Biology and Biotechnology, University of Perugia, via Elce di Sotto 8, I-06123 Perugia, Italy
e, Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Istituto CNR di Scienze
f, Humboldt Universität zu Berlin, Institut für Chemie, AG NMR, Germany, Brook-Taylor-Straße, 2, Berlin, DE
g, CompuNet, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
Abstract

Solvents for processing stable tin halide perovskites

 

Perovskite solar cells are the most promising PV technology in recent years. Efficiency rocketed from 3.1% to 25.5% in 10 years of intensive research. The highest performing PSCs are lead-based, which increases concerns about the environmental impact of this type of solar cell. PSCs community started to direct their interest towards tin-based perovskites as an efficient alternative to the lead counterpart. However, tin perovskites are hindered by the tin (II) oxidation to tin (IV), which leads to self-doping and devastating cell performance. The highest performing tin perovskites are based on dimethylsulfoxide (DMSO) as a solvent. Recently, many reports proved that DMSO is a primary source of tin oxidation. The quest for a novel solvent could be the gamechanger in the stability of tin-based perovskites. Starting from a database of over 2000 solvents, we identified a series of 12 new solvents suitable for the processing of formamidinium tin iodide perovskite (FASnI3) experimentally by investigating 1) the solubility of the precursor chemicals FAI and SnI2, 2) the thermal stability of the precursor solution and 3) the possibility to form perovskite. Finally, we demonstrate a novel solvent system to produce solar cells outperforming those based on DMSO. Our work provides guidelines for further identification of new solvents or solvent mixtures for preparing stable tin-based perovskites.

12:25 - 12:35
Abstract not programmed
12:35 - 12:45
Abstract not programmed
12:45 - 13:15
Discussion
13:05 - 14:00
NanoLight Break
13:05 - 15:15
PERIMPED Break
13:05 - 14:05
SOLFUL Break
13:15 - 15:15
TINPERO Break
14:00 - 14:10
NanoLight Session 1.3 Introduction by Alexander Urban
14:05 - 14:10
Opening nanoGe SOLFUL
14:10 - 14:15
CHEMNC nanoGe Introduction
NanoLight 1.3
Chair: Alexander Urban
14:10 - 14:30
1.3-I1
Moreels, Iwan
Gent University - BE
Diving into the blue: synthesis and opto-electronic properties of thin CdSe nanoplatelets
Moreels, Iwan
Gent University - BE, BE

I obtained my PhD degree in applied physics at Ghent University in 2009, studying near-infrared lead salt quantum dots. This was followed by a postdoc on quantum dot emission dynamics at Ghent University in collaboration with the IBM Zurich research lab. In 2012 I joined the Istituto Italiano di Tecnologia, where I led the Nanocrystal Photonics Lab in the Nanochemistry Department. In 2017 I returned to Ghent University as associate professor, focusing mostly on 2D and strained nanocrystals. The research in our group ranges from the synthesis of novel fluorescent nanocrystals to optical spectroscopy and photonic applications.

Authors
Iwan Moreels a
Affiliations
a, Department of Chemistry, Ghent University, Belgium, Krijgslaan 281-S3, Ghent, BE
Abstract

Two-dimensional fluorescent colloidal nanocrystals combine the flexibility of solution-processed nanomaterials with the advantages of a (quasi-)2D band structure that offers enhanced optical properties compared to 0D quantum dots. CdSe is at present the most established 2D nanoplatelet material, yet, while several procedures are available for highly luminescent 4.5 monolayer and thicker NPLs with emission spanning the green and red spectral region, typical synthesis protocols to prepare blue-emitting CdSe NPLs (λ ≈ 460 nm) yields NPLs with large surface areas and poor fluorescence quantum efficiencies, often accompanied by strong emission from intragap trap states.

Here we present our work on the development of a synthesis protocol that achieves improved control over the lateral size, by exploiting a series of long-chained carboxylate precursors. The length of the metallic precursor is key to tune the width and aspect ratio of the NPLs (from 3:1 to 15:1), as well as the overall reaction yield, which increases for shorter chain length. The reduced NPL lateral dimensions lead to enhanced photoluminescence quantum efficiencies, reaching up to 30%, and good colloidal stability. Combined with a reduced contribution from Rayleigh scattering, we were able to further investigate the opto-electronic properties, and demonstrate that the blue-emitting NPLs are characterized by faster emission lifetimes, a higher absorption coefficient, yet do not show a significant increase in exciton binding energy compared to thicker nanoplatelets.

Via a slight adjustment, we also obtained 2.5 monolayers NPLs, with near-UV emission (λ ≈ 400 nm), and a quantum efficiency up to 11%. Our results thus contribute to achieving stable and efficient sources for applications such as blue and UV light emitting devices or lasers, or fast quantum light sources.

14:30 - 14:50
1.3-I2
Buonsanti, Raffaella
Ecole Polytechnique Federale de Lausanne (EPFL)
Metal oxide shells for quantum dots by colloidal atomic layer deposition
Buonsanti, Raffaella
Ecole Polytechnique Federale de Lausanne (EPFL), CH

Raffaella Buonsanti obtained her PhD in Nanochemistry in 2010 at the National Nanotechnology Laboratory, University of Salento. Then, she moved to the US where she spent over five years at the Lawrence Berkeley National Laboratory, first as a postdoc and project scientist at the Molecular Foundry and after as a tenure-track staff scientist in the Joint Center for Artificial Photosynthesis. In October 2015 she started as a tenure-track Assistant Professor in the Institute of Chemical Sciences and Engineering at EPFL. She is passionate about materials chemistry, nanocrystals, understanding nucleation and growth mechanisms, energy, chemical transformations.

Authors
Raffaella Buonsanti a
Affiliations
a, EPFL École Polytechnique Fédérale de Lausanne, Laboratory of Nanochemistry for Energy, Department of Chemical Science and Engineering, Switzerland, Sion, CH
Abstract

Because of their tunable optical properties, quantum dots have emerged as technologically relevant materials for efficient optoelectronic devices, as a matter of fact they are now even integrated in LED televisions, and biological applications. However, they are often unstable in the environment or during their processing. Oxide shells can aid to overcome this issue, yet method to synthesize them in a controlled manner, with tunable composition and thickness, are still scarce.

In this talk, I will focus on our recently developed colloidal atomic layer deposition approach to grow tunable oxide shells around nanocrystals, including quantum dots. I will discuss the formation mechanism of the shell by sharing our recent insights into the surface chemistry. Then I will show that these oxide shells, because of their tunability, enable fundamental studies of energy transfer and can improve our understanding of ion exchange reactions. Finally, I will also demonstrate some of the enabled applications, such as the improved stability of the colloidal ink in addition to the enhanced resistance against harsh environment (i.e. water and heat).

14:50 - 15:10
1.3-I3
Norris, David
Swiss Federal Institute of Technology ETH Zurich
The Fluorescence Linewidth of CdSe-Based Nanoplatelets
Norris, David
Swiss Federal Institute of Technology ETH Zurich, CH

David J. Norris is currently the Director of the Optical Materials Engineering Laboratory and Professor of Materials Engineering at ETH Zurich. He received his B.S. and Ph.D. degrees in Chemistry from the University of Chicago (1990) and MIT (1995), respectively. After an NSF postdoctoral fellowship at the University of California, San Diego, he joined the NEC Research Institute in Princeton in 1997 where he led a photonics research group. He then became an Associate Professor (2001-2006) and Professor (2006-2010) of Chemical Engineering and Materials Science at the University of Minnesota. In 2010, he moved to his current position at ETH Zurich. Prof. Norris is a Fellow of the American Physical Society and the American Association for the Advancement of Science. He received the Golden Owl award at ETH in 2012 for excellence in teaching. He was awarded an Advanced Grant from the European Research Council (2014-2019). In 2015, he was the recipient of the Max R�ssler Prize.

Authors
David Norris a
Affiliations
a, Optical Materials Engineering Laboratory, ETH Zürich, Switzerland, Leonhardstrasse, 21, Zürich, CH
Abstract

Colloidal nanoplatelets (NPLs) are atomically flat, quasi-two-dimensional particles of semiconductor. Despite intense interest in their optical properties, several observations concerning their emission remain puzzling. In particular, while ensembles of CdSe NPLs show remarkably narrow photoluminescence linewidths at room temperature, adding a CdS shell to increase their fluorescence efficiency and photostability causes significant linewidth broadening. In this talk, we will discuss recent experiments where we have been working to understand the NPL linewidth. We examine the emission of both core-only and core/shell NPLs as a function of temperature and time. Further, emission from core/shell particles is collected at the individual NPL level. At cryogenic temperatures, we observe surprisingly complex emission spectra that contain multiple spectrally narrow emission features that change during the experiment. Our results indicate that additional charges play a critical role in the observed emission behavior. Specifically, we find that the linewidth complexity is consistent with negatively charged excitons (trions) and the appearance of electron “shakeup lines”.

15:10 - 15:30
Discussion
SOLFUL 1.3
Chair not set
14:10 - 14:20
1.3-T1
Driencourt, Luc
CSEM Muttenz, Swiss Center for Electronics and Microtechnology
Modelling enhanced performances by optical nanostructures in water splitting photoelectrodes
Driencourt, Luc
CSEM Muttenz, Swiss Center for Electronics and Microtechnology
Authors
Luc Driencourt a, b, c, Benjamin Gallinet b, Catherine Housecroft a, Sören Fricke b, Edwin Constable a
Affiliations
a, Department of Chemistry, University of Basel, Spitalstrasse, 51, Basel, CH
b, CSEM Muttenz, Swiss Center for Electronics and Microtechnology, Tramstrasse 99, Muttenz, 4132
c, Swiss Nanoscience Institute, University of Basel, Switzerland, CH
Abstract

Material nanostructuring and optical phenomena at the nanoscale such as plasmonic effects and light scattering have been widely studied for improving the solar-to-hydrogen conversion efficiency of photoelectrochemical water splitting electrodes [1, 2]. In this presentation, we report a method for studying optical enhancement from nanostructures and its contribution to the photocatalytic performances. It involves precise optical modelling, computation of the light distribution in the photoelectrode and a simplified treatment of the separation, transport and transfer of the charge carrier. This enables an accurate description of the optical effects while limiting the computational cost. The method is validated on several experimentally fabricated photoelectrodes. For each case, the optical model and the optical properties of the materials are first validated by comparison with measurements. The studied geometries involve several semiconductor materials (hematite and bismuth vanadate) different types of optical elements (periodically distributed host scaffolds, randomly distributed nanoparticles) and different electromagnetic simulation methods (rigorous coupled wave analysis and surface integral equations). A very good qualitative and quantitative agreement between the calculated and measured optical enhancement of the photoelectrochemical performances is obtained for both periodic and random structures. The developed method is applicable to a wide variety of systems and optical simulation methods. In particular, we demonstrate the contribution of resonant plasmonic and non-resonant scattering to the optical enhancement.

14:20 - 14:30
1.3-T2
Mesa, Camilo A.
Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain
Spectroelectrochemical analysis of the water oxidation mechanisms on metal oxide electrocatalysts
Mesa, Camilo A.
Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, ES
Authors
Camilo A. Mesa a, Laia Francàs b, Sacha Corby c, Miguel Garcia-Tecedor a, James R. Durrant c, Sixto Gimenez a
Affiliations
a, Institute of Advanced Materials (INAM), University Jaume I, Castellon, Spain
b, Departament de Química, Universitat Autònoma de Barcelona, Barcelona, Spain
c, Molecular Sciences Research Hub (MSRH), Imperial College London, London, U.K.
Abstract

Electrocatalytic water splitting is considered a promising technology to store renewable energy into chemical bonds (e.g., hydrogen). In this process, the oxygen evolution reaction (OER) water acts as electron donor and it is considered to be the bottleneck of the process when using metal-oxide (photo)anodes. The efficiency of these catalysts does not only depend on the nature of the metal oxide, but also on their physical characteristics such as thickness and porosity and doping variations, amongst others. However, the mechanism of the OER on metal oxides as well as the nature of the efficiency loses and the role of charge accumulation in electrocatalysts is yet to be well understood [1].

In this talk, I will present recent advances on the understanding of the kinetics of OER on different metal-oxide electrocatalysts, focusing particularly on Ni-based anodes. A mechanistic analysis of the OER on Ni-based electrocatalysts will be presented by the study of the water oxidation rate law under different physicochemical conditions, Fe incorporation [2,3] and when combined with a photoelectrode for solar-driven fuel synthesis.

14:30 - 14:40
1.3-T3
Caspary Toroker, Maytal
Breakdown of the polaron model in ternary spinel oxides
Caspary Toroker, Maytal
Authors
Maytal Caspary Toroker a
Affiliations
a, Department of Materials Science and Engineering, Technion – Israel Institute of Technology, Haifa, 3200003, Israel
Abstract

The small-polaron hopping model has been used for several decades for modeling electronic charge transport in oxides. Despite its significance, the model was developed for binary oxides, and its accuracy has not been rigorously tested for higher-order oxides. To investigate this issue, we chose the MnxFe3-xO4 spinel system, which has exciting electrochemical and catalytic properties, and mixed cation oxidation states that enable us to examine the mechanisms of small-polaron transport. Using a combination of experimental results and DFT+U calculations, we find that the charge transport occurs only between like-cations (Fe/Fe or Mn/Mn). And due to asymmetric hopping barriers and formation energies, we find that the MnOh2+ polaron is energetically preferred to the FeOh2+ polaron, resulting in an asymmetric contribution of the Mn/Mn pathways.

 

Reference:

A. Bhargava, R. Eppstein, J. Sun, M. A. Smeaton, H. Paik, L. F. Kourkoutis, D. G. Scholm, M. Caspary Toroker*, R. D. Robinson*, “Breakdown of the small-polaron hopping model in higher-order spinels”, Adv. Mat., 2004490 (2020).

14:40 - 14:50
1.3-T4
Vinogradov, Ilya
Characterizing the First Oxygen Evolution Reaction Intermediate with Picosecond Transient Optical and Acoustic Spectroscopies
Vinogradov, Ilya
Authors
Ilya Vinogradov a, Suryansh Singh a, Hanna Lyle a, Aritra Mandal a, Jan Rossmeisl b, Tanja Cuk a
Affiliations
a, Renewable and Sustainable Energy Institute (RASEI), University of Colorado, Boulder
b, University of Copenhagen, Department of Chemistry
Abstract

For the oxygen evolution reaction (OER), reaction intermediates are theoretically defined by reactive oxygen species separated by electron-proton transfer steps. These catalytic steps are characterized by their thermodynamic free energy differences, a quantity not easy to access experimentally. In this talk, I will describe recent results that demonstrate a route toward accessing this thermodynamic quantity. These results were acquired for a model titania system (Nb-doped SrTiO3) using our in situ photoelectrochemical picosecond visible transient reflectance spectrometer. We have discovered that varying the OER’s electrolyte pH modulates the population of the first reactive oxygen intermediate, formed within 2 ps.  By fitting the population’s dependance on pH to a Langmuir isotherm model, we found that we could assign an effective equilibrium constant relatable to the free energy change of the first OER charge transfer step. In addition, I will present experimental data that characterizes the first intermediate in terms of its GHz acoustic signature. In this work, we used picosecond acoustic interferometry to find that hole trapping, which creates the first OER intermediate, is concomitant with the generation of a subsurface strain. The timescale of strain generation and hole trapping at the surface is independently well characterized to be 1.3 ps. These results will help provide a physical model for the transient conditions under which OER intermediates exist and will help bridge the gap between theoretical descriptors of OER intermediates and experimentally accessible quantities.

14:50 - 15:20
Discussion
CHEMNC 1.2
Chair: Marcus Scheele
14:15 - 14:25
1.2-T1
De Roo, Jonathan
Department of Chemistry, University of Basel
Anthracene Diphosphate Ligands for CdSe Quantum Dots; Molecular Design for Efficient Upconversion
De Roo, Jonathan
Department of Chemistry, University of Basel, CH
Authors
Jonathan De Roo a, Zhiyuan Hang c, Nathaniel Schuster b, Dan Congreve d, Zihao Xu e, Dmitry Fishman f, Tianquan Lian e, Jonathan Owen b, Ming Lee Tang f
Affiliations
a, Department of Chemistry, University of Basel, Spitalstrasse, 51, Basel, CH
b, Department of Chemistry, Columbia University, US, Broadway, 3000, New York, US
c, Department of Chemistry, University of California Riverside, United States., US
d, Rowland Institute at Harvard, Massachusetts, US, Edwin H Land Boulevard, 100, Cambridge, US
e, Department of Chemistry, Emory University, 1515 Dickey Drive NE, Atlanta, Georgia 30322, USA
f, Department of Chemistry, University of California, Irvine, Irvine, California 92617, EE. UU., Irvine, US
Abstract

Nanocrystal surface chemistry, i.e., the understanding of and control over the ligand shell, has become one of the central themes in nanocrystal research. For example, in quantum dot sensitized photon upconversion, a multi-step process takes place where energy is transferred from the quantum dot to a surface-bound ligand (the transmitter) and finally to a soluble annihilator. Typically, 9-anthracene carboxylic acid is used as the transmitter ligand, reaching 14 % upconversion efficiency with CdSe quantum dots.

Here,[1] in an effort to design a high-affinity ligand, we developed the five-step synthesis of anthracene 10-R-anthracene-1,8-diphosphoric acid (R = octyl, 2-hexyldecyl, phenyl). Using 1H NMR spectroscopy we demonstrate that these bidentate diphosphate ligands rapidly and irreversibly displace two carboxylate ligands, showcasing their high binding affinity. Subsequently, using CdSe as nanocrystal sensitizer and 1,10-diphenylanthracene as a triplet annihilator, we demonstrate a photon upconversion process that is limited by the transmitter to annihilator transfer efficiency. Our custom designed transmitter ligands mediate energy transfer from the photoexcited QDs to the triplet annihilator, producing overall photon upconversion quantum efficiencies as high as 17%, the highest for quantum dots without shells. Transient absorption spectroscopy suggests that our transmitter ligand supports a long triplet state lifetime, increasing the probability of energy transfer.

In conclusion, we have developed a novel bidentate ligand with a designed high binding affinity for nanocrystal surfaces. We also showed that transmitter ligand structure is critical to boosting the photon upconversion quantum yields. Finally, we are currently developing the next generation of high-affinity ligands, including tetradentate macrocycles.

 [1] De Roo, J.; Huang, Z.; Schuster, N. J.; Hamachi, L. S.; Congreve, D. N.; Xu, Z.; Xia, P.; Fishman, D. A.; Lian, T.; Owen, J. S.; Tang, M. L., Anthracene Diphosphate Ligands for CdSe Quantum Dots; Molecular Design for Efficient Upconversion. Chem. Mat. 2020, 32 (4), 1461-1466.

14:25 - 14:35
1.2-T2
Calcabrini, Mariano
IST Austria
Exploiting the Lability of Metal Halide Perovskites for Doping Semiconductor Nanocomposites
Calcabrini, Mariano
IST Austria, AT
Authors
Mariano Calcabrini a, Aziz Genç b, c, Yu Liu a, Tobias Kleinhanns a, Seungho Lee a, Dmitry N. Dirin d, e, Quinten A. Akkerman d, e, Maksym V. Kovalenko d, e, Jordi Arbiol b, f, Maria Ibáñez a
Affiliations
a, Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
b, Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Catalonia, Spain
c, Materials Science and Engineering Department, Izmir Institute of Technology, İzmir, Turkey
d, Department of Chemistry and Applied Biosciences, ETH Zürich, Zurich CH-8093, Switzerland
e, Empa-Swiss Federal Laboratories for Materials Science and Technology, Zurich CH-8600, Switzerland
f, ICREA, Pg. Lluís Companys 23, Barcelona 08010, Catalonia, Spain
Abstract

Cesium lead halides exhibit diverse bonding nature with covalent PbX64- anions and Cs+ cations. These ions' low charge density renders the crystals unstable, enabling the conversion between related perovskites and non-perovskites phases. [1] Such instability can be problematic for some applications like photovoltaics and detectors where the perovskites are exposed to high energy densities, but is this always a disadvantage?

Our most recent work shows how CsPbBr3 converts to Cs4PbBr6 upon heating up with PbS producing PbS-Cs4PbBr6 nanocomposites. [2] The byproduct of the transformation, PbBr2, dissolves in the PbS matrix, increasing the carrier concentration and inducing grain growth. In this presentation, we provide evidence of the chemical transformation using temperature-dependent in-situ X-ray diffraction and high resolution transmission electron microscopy. Additionally, by controlling the amount of CsPbBr3, we tune the charge carrier density between 1019 and 1020 cm-3. Such heavily doped nanocomposites have potential applications in thermoelectrics and optoelectronic devices. Furthermore, this doping strategy is not limited to cesium lead halides and could be applied to other unstable crystal phases.

14:35 - 14:45
1.2-T3
Paritmongkol, Watcharaphol
Massachusetts Institute of Technology (MIT)
Tunable Morphology and Electronic Properties of Hybrid Organic-Inorganic 2D Semiconducting AgSePh
Paritmongkol, Watcharaphol
Massachusetts Institute of Technology (MIT), US

PhD student in the Tisdale lab at Massachusetts Institute of Technology

Authors
Watcharaphol Paritmongkol a, b, Woo Seok Lee b, c, Wenbi Shcherbakov-Wu a, b, Seung Khun Ha b, Tomoaki Sakurada b, Soong Ju Oh d, William Tisdale b
Affiliations
a, Department of Chemistry, Massachusetts Institute of Technology
b, Department of Chemical Engineering, Massachusetts Institute of Technology
c, Department of Materials Science and Engineering, Massachusetts Institute of Technology
d, Department of Materials Science and Engineering, Korea University
Abstract

Silver phenylselenolate (AgSePh) is an emerging two-dimensional semiconducting member of a hybrid metal-organic chalcogenolate family. In addition to its narrow blue photoluminescence, in-plane anisotropy, and high exciton binding energy, the synthesis of AgSePh thin films is potentially scalable by a vapor-phase chemical transformation. Because the properties of polycrystalline thin-film semiconductors are influenced by their crystal orientation and size, controlling these two attributes is important for electronic applications as well as fundamental studies. Herein, we show by testing 24 solvent vapors – with different polarities, boiling points, and functional groups – that the addition of solvent vapor during the synthesis influences crystal orientation with respect to a substrate surface. Using solvent vapor molecules that are known to form complexes with silver ions, such as dimethyl sulfoxide, can also lead to an increase in the polycrystalline size from ~200 nm to >1 µm without altering the chemistry of the final film products. Moreover, we find that introducing dimethyl sulfoxide vapor results in a AgSePh thin film with a lower dark current and higher photoconductivity, suggesting an improved intrinsic property of a semiconductor with fewer mid-gap states. The existence of these mid-gap states is confirmed by 1) subgap-excitation photo-responses in photoconductivity measurements and 2) mid-gap emission in low-temperature photoluminescence spectroscopy. The improved synthesis of AgSePh thin films by solvent vapor addition with controllable morphology, increased crystal size, and suppressed mid-gap states, reported in this work, can serve as a model system that may lead to the development of thin-film technology of other hybrid metal-organic chalcogenolate semiconductors and the syntheses of other materials by chemical vapor transformation.

14:45 - 15:15
Discussion
15:15 - 15:20
CHEMNC Break
15:15 - 15:20
DSSC Opening nanoGe
15:15 - 15:20
PERIMPED Opening nanoGe
15:15 - 15:20
TINPERO Opening nanoGe
15:20 - 15:30
CHEMNC Session Introduction 1.3
15:20 - 15:30
DSSC Session Introduction 1.2
15:20 - 15:30
PERIMPED Session Introduction 1.3
15:20 - 15:30
SOLFUL Session Introduction 1.4
15:20 - 15:30
TINPERO Session Introduction 1.3
CHEMNC 1.3
Chair: Maksym Yarema
15:30 - 15:50
1.3-I1
Gogotsi, Yury
Drexel University
Chemical and Structural Diversity of 2D Carbides and Nitrides (MXenes)
Gogotsi, Yury
Drexel University, US
Authors
Yury Gogotsi a
Affiliations
a, Yury Gogotsi, Drexel University, Philadelphia, PA 19104, USA
Abstract

2D carbides and nitrides, known as MXenes, are among the most recent, but quickly expanding material families. The field is experiencing very fast growth with more than 30 stoichiometric MXenes and at least 20 solid solutions reported. Major breakthroughs have been achieved in the past 2-3 years, including new methods of synthesis, improved control of surface terminations, the discovery of 2D M5C4 carbides with twinned layers and CVD synthesis of MoSi2N4, representing a new family of 2D nitrides. Synthesis of dozens of predicted MXenes having metallic conductivity combined with hydrophilicity and redox activity led to numerous applications. Reversible redox activity of transition metal atoms in the outer layers of MXene flakes combined with high electronic conductivity led to applications in batteries and electrochemical capacitors. MXenes are promising candidates for energy storage and related electrochemical applications, but applications in optoelectronics, plasmonics, electromagnetic interference shielding, electrocatalysis, medicine, sensors, or water purification are equally exciting. This presentation will focus on synthesis of MXenes with diverse chemical compositions and structures, as well as the effect of material chemistry on properties. Particular attention will be paid to solid solutions and fine tuning of MXene properties by varying the ratio of transition metals in the solid solution.

 

15:50 - 16:10
1.3-I2
Reiss, Peter
CEA Grenoble INAC
Highly fluorescent silver indium sulfide quantum dots: batch vs. continuous flow aqueous synthesis
Reiss, Peter
CEA Grenoble INAC, FR

Peter Reiss is researcher at the Institute of Nanoscience & Cryogenics, CEA Grenoble, and Head of Laboratory of Molecular, Organic and Hybrid Electronics (LEMOH). He graduated (1997) from University of Karlsruhe, Germany, and earned his PhD in inorganic chemistry under the supervision of Prof. Dieter Fenske (2000). His research activities focus on the development of synthesis methods for different kinds of colloidal nanocrystals and semiconductor nanowires, the surface functionalization of nanocrystals by “tailor-made” ligands resulting in novel nanoscale building blocks and the assembly of these building blocks into structurally controlled functional materials for optoelectronics. The studied applications range from fluorescent markers for biological labelling and detection over the development of efficient emitters for LEDs and displays to new strategies for nanocrystal based energy conversion and storage. Dr. Reiss acts as Associate Editor for Nanoscale Research Letters and Journal of Nanomaterials and co-organizes the international conference series « NaNaX – Nanoscience with Nanocrystals ».

Authors
Peter Reiss a, Annette Delices a, Davina Moodelly a, Yanxia Hou a, Kuntheak Keng a, Céline Rivaux a
Affiliations
a, Univ. Grenoble Alpes, CEA, CNRS, IRIG, SyMMES, FR
Abstract

Research on novel types of fluorescent colloidal quantum dots (QDs) free of toxic heavy metals has led to the discovery of emission properties strongly differing from those of classical II-VI or III-V semiconductor nanocrystals. One example is the case of chalcopyrite-type I-III-VI2 quantum dots, whose broad fluorescence band and large Stokes shift have been attributed to optical transitions implying localized intra-bandgap states.[1] In this family of materials, silver indium sulfide (AIS) nanocrystals have attracted particular attention due to their elevated PLQY and long PL lifetime. It is also one of the scarce examples of strongly emissive QDs directly synthesized in aqueous medium. Our study aims at the reduction of the emission line width, the increase of PLQY and the in situ biofunctionalization of AIS QDs synthesized in water.

            The generally applied heat-up approach leads to a broad size distribution necessitating post-synthetic size fractionation procedures. To achieve better size control, we explored fast and slow injection of the Ag and S precursors into a hot solution of the In precursor. Both methods surprisingly led to a completely different behavior in terms of size, stoichiometry and crystal structure of the obtained AIS QDs and gave direct access to size distributions on the order of 10%. After capping with a ZnS shell, near infrared PL with a QY of 55-70% and a long decay time of 900 ns was obtained. Bioconjugation with thiol-modified DNA was realized in situ during ZnS shell growth, and confirmed by surface plasmon resonance (SPR) imaging using complementary DNA strands.[2]

            To further investigate the influence of the different synthetic parameters, we developed the continuous flow synthesis of AIS and AIS/ZnS QDs. This approach enables a much better heat and mass transfer than batch syntheses, steeper temperature profiles, the use of increased pressure, and assures excellent reproducibility. The best combinations of parameters gave access to AIS/ZnS QDs with PLQYs exceeding 80%.

            Finally, the synthetic scheme was translated to Ag2S nanocrystals, exhibiting near infrared emission in the 800-1200 nm range, which is of particular interest for in vivo biological imaging.

16:10 - 16:30
1.3-I3
Talapin, Dmitri
University of Chicago
Molten Inorganic Salts as Solvents for Colloidal Synthesis of Low-Dimensional Materials
Talapin, Dmitri
University of Chicago, US
Dmitri Talapin is a Professor of Chemistry at University of Chicago. His research interests revolve around inorganic nanomaterials, spanning from synthetic methodology to device fabrication, with the desire of turning colloidal nanostructures into competitive materials for electronics and optoelectronics. He received his doctorate degree from University of Hamburg, Germany in 2002 under supervision of Horst Weller. In 2003 he joined IBM Research Division at T. J. Watson Research Center as a postdoctoral fellow to work with Chris Murray on synthesis and self-assembly of semiconductor nanostructures. In 2005 he moved to Lawrence Berkeley National Laboratory as a staff scientist at the Molecular Foundry and finally joined faculty at the University of Chicago in 2007. His recent recognitions include MRS Outstanding Young Investigator Award (2011); Camille Dreyfus Teacher Scholar Award (2010); David and Lucile Packard Fellowship in Science and Engineering (2009); NSF CAREER Award (2009) and Alfred P. Sloan Research Fellowship (2009).
Authors
Wooje Cho a, Aritrajit Gupta a, Vladislav Kamysbayev a, Dmitri Talapin a
Affiliations
a, Department of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
Abstract

Many functional materials are synthesized by solution-phase chemical reactions. The scope of chemical transformations that can be performed in a solution environment is determined by the stability of solvents and surfactants used as a reaction medium. For example, very few traditional solvents can handle temperatures above 400 C, while many inorganic phases require even higher temperatures to form. A novel class of colloidal systems, colloids in molten inorganic salts, bring new opportunities to the field of solution synthesis because of unmatched thermal stability and chemical inertness. We are developing molten inorganic salts as versatile media for unprecedented colloidal and solid-state chemistry of low-dimensional materials.

The phenomenon of colloidal stability in molten salts cannot be explained by traditional electrostatic and steric stabilization mechanisms [1]. Colloids in molten salts likely form through a novel mechanism responsible for repulsive interparticle potentials. The experimental studies and simulations point to the importance of the long-range ion correlations in the molten salt induced by the crystal surface [2]. Unique properties of molten inorganic salts allowed us to synthesize previously inaccessible colloidal III-V gallium-indium phosphide and arsenide quantum dots [3]. The molten salts also enable unprecedented surface chemistry for two-dimensional transition metal carbides (MXenes), with a potential for improved energy storage characteristics and superconductivity [4]. The developed methods are expected to be applicable to other hard-to-crystallize nanomaterials that have been out of reach for colloidal chemists.

16:30 - 16:50
1.3-I4
Schimpf, Alina
University of California San Diego
Aminophosphine-Based Synthesis of Colloidal Copper Phosphide Nanocrystals
Schimpf, Alina
University of California San Diego, US
Authors
Alina Schimpf a, Alexander Rachkov a
Affiliations
a, University of California San Diego, Gilman Drive, 9500, San Diego, US
Abstract

Colloidal copper phosphide (Cu3−xP) nanocrystals are attractive materials due to their ability to support excess delocalized holes, leading to localized surface plasmon resonance (LSPR) absorption in the near-IR. This talk will present a one-pot, colloidal synthesis of Cu3−xP nanoplatelets from copper halide salts and tris(diethylamino)phosphine (P(NEt2)3) in the presence of oleylamine (OAm) and trioctylamine. An in-situ copper−phosphorus precursor is identified by mass spectrometry, providing insight into the pre-nucleation chemistry that leads to metal–phosphide bond formation. The final nanocrystal ensemble can be tuned by varying the precursor ratios and identities or by changing the temperature. With this synthesis, nanocrystals with lateral sizes of 6.1–23 nm with LSPR energies of 709–861 meV can be accessed. Overall, this synthesis presents a platform for systematic mechanistic investigations of the chemical processes underlying Cu3−xP nanocrystal formation. The low polydispersity, size- and LSPR-tunability and colloidal stability make these nanocrystals promising candidates for further investigations into factors governing the LSPR energy in Cu3−xP nanomaterials.

16:50 - 17:10
Discussion
DSSC 1.2
Chair: Jared Delcamp
15:30 - 15:50
1.2-I1
Galoppini, Elena
Rutgers University Chemistry Department
Dual-Linker Sensitizers: Conformational and Binding Effects on Interfacial Electron Transfer
Galoppini, Elena
Rutgers University Chemistry Department, US

Elena Galoppini was born in Pisa, Italy. She received a Laurea in Chimica from the Università di Pisa, and a Ph.D. from the University of Chicago (synthesis and reactivity of ethynylcubanes, strained cage molecules). She was then a Postdoctoral Fellow at the University of Texas at Austin, where she synthesized and studied the effect of the helix dipole on electron transfer processes in donor-spacer-acceptor systems made from peptides. She joined as Assistant Professor the Chemistry Department at Rutgers University-Newark, where she is Distingushed Professor since 2017. She a the recipent  of  the 2019 Rutgers Board of Trustees Award for Excellence in Research and has authored over 100 papers and review articles. The research interests of her group are centered on the design and synthesis of model chromophoric compounds to study electronic processes on nanostructured semiconductor materials. This research finds application in the development of functional nanomaterials, including new types of solar cells, electrochromic windows and biosensors.

Authors
Elena Galoppini a, Luis Rego b, Lars Gundlach c
Affiliations
a, Rutgers University Chemistry Department, Warren Street, 73, Newark, US
b, Universidade Federal de Santa Catarina - UFSC, Brazil, R. Eng. Agronômico Andrei Cristian Ferreira, s/n - Trindade, Florianópolis, BR
c, University of Delaware, 127 The Green, RM 201, Newark, US
Abstract

The quest to control chromophore/semiconductor properties to enable new technologies in the energy and information science requires detailed understanding of interfacial charge carrier dynamics at the atomistic level, which can be often attained through the use of chromophore-bridge-anchor model systems. These models have been employed for decades, but there are emerging concepts in the use of the bridge-anchor groups.  The talk will focus on this area, particularly the use of functionally active linkers, focusing on our recent work on dual linkers.   We will discuss perylene-bridge-anchor compounds with one or two linker units in both the peri and ortho positions. A combination of photophysical characterization and computational analysis in solution and on semiconductor surfaces were used to probe the influence of the number of linkers (one vs. two), their structure (conjugated, saturated) and their substitution position (ortho vs. peri). This study shows that small conformational changes and vibrational coupling differ between each linker and can have significant influence on interfacial charge transfer, even on the femtosecond time scale, suggesting that the molecular design of multiple linkers that differ in bonding strength, and serve different functions, opens up new avenues for controlling charge transfer dynamics.

15:50 - 16:10
1.2-I2
meyer, gerald
UNC-Chapel Hill
TRANSPARENT CONDUCTIVE OXIDES FOR FUNDAMENTAL ANALYSIS OF DYE-SENSITIZATION
meyer, gerald
UNC-Chapel Hill, US
Authors
gerald meyer a
Affiliations
a, University of North Carolina at Chapel Hill, Department of Chemistry, Chapel Hill, Carolina del Norte 27599, EE. UU., Chapel Hill, US
Abstract

Transparent conductive oxides (TCOs) are commercially available and versatile photoelectrode materials with some distinct advantages over semi-conducting oxides. The high doping level of TCOs such as In2O3:Sn (ITO) (ND > 1020 cm−3) exhibit metallic properties that include high electron mobility and conductivity while retaining high transparency in the visible region for dye-sensitization applications. Regenerative solar cell applications are generally precluded as dye-sensitized electron transfer does not significantly impact the TCO quasi-Fermi levels and negligibly small open circuit photovoltages and power conversion efficiencies result. Nevertheless, the TCO materials allow potentiostatic control of the Fermi level that enables experimental determination of the free energy dependence for dye-sensitized electron transfer kinetics. Marcus-Gerischer analysis of such kinetics provides quantitative measure of the fundamental electronic couplings and reorganization energies and valuable insights into interfacial electron transfer mechanisms.

Mesoporous thin films of ITO nanocrystallites electrodes have been shown to support remarkably long-lived (~ 1 s) charge separation after dye-sensitized electron transfer with first-order kinetics that are competent of water oxidation.[1,2] The key to success was to spatially position a molecular sensitizer and redox or catalytic molecules distant from the conductive surface. Specific focus on an unwanted interfacial electron transfer reaction with a molecular water oxidation catalyst revealed a 0.4 eV smaller reorganization energy for electron transfer λET than for proton-coupled electron transfer λPCET.[3] Systematic analysis of distance dependent interfacial electron transfer, utilizing a layer-by-layer approach to spatially position redox active molecules within the electric double layer, provided a startling result: The barrier for electron transfer was near zero for molecules located within the Helmholtz planes. [4,5] The kinetic data could not be modelled with dielectric continuum models and indicated a substantially decreased solvent dielectric constant at the dye-sensitized ITO interface. [6]

This presentation will describe Marcus-Gerischer theory as context for new and recently published dye-sensitized electron transfer reactions.

16:10 - 16:30
1.2-I3
Houle, Frances
Lawrence Berkeley National Laboratory
Connecting Molecular Processes to System Characteristics in Dye-Sensitized Photoanodes
Houle, Frances
Lawrence Berkeley National Laboratory, US
Authors
Frances Houle a
Affiliations
a, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA, Berkeley, US
Abstract

Photocurrent generation and transport in dye-sensitized photoelectrodes involve molecular-level physical and chemical processes whose interconnections determine the efficiency of the system. Important aspects of how local, molecular-level events influence operations at the scale of many microns are revealed using multiscale reaction-diffusion simulations. In this talk, the basic kinetic framework used for the calculations will be introduced, with a focus on molecular transport and charge cycling within the photoanode as a function of electrolyte composition and dye excitation frequency. Based on known chemistry and diffusion characteristics, the simulations show that neither transport within the pores nor electron-electrolyte recombination processes directly control photocurrent under all conditions. Processes at the cathode are much more important. Current work on understanding how the details of dye photophysics under diffuse, broadband solar irradiation influence the system will be described.

16:30 - 16:50
Discussion
NanoLight 1.4
Chair: Alexander Urban
15:30 - 15:40
1.4-T1
Hinterding, Stijn O.M.
Utrecht University
Single Trap States in Single CdSe Nanoplatelets
Hinterding, Stijn O.M.
Utrecht University, NL
Authors
Stijn O.M. Hinterding a, b, Bastiaan B.V. Salzmann c, Sander J.W. Vonk a, b, Daniël Vanmaekelbergh c, Bert M. Weckhuysen b, Eline M. Hutter b, Freddy T. Rabouw a, b
Affiliations
a, Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584CC Utrecht, The Netherlands
b, Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584CG Utrecht, The Netherlands
c, Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584CC Utrecht, The Netherlands
Abstract

Trap states can strongly affect semiconductor nanocrystals, by quenching, delaying, and spectrally shifting the photoluminescence (PL). Trap states have proven elusive and difficult to study in detail at the ensemble level, let alone in the single-trap regime. CdSe nanoplatelets (NPLs) exhibit significant fractions of long-lived “delayed emission” and near-infrared “trap emission”. We use these two spectroscopic handles to study trap states at the ensemble and the single-particle level. We find that reversible hole trapping leads to both delayed and trap PL, involving the same trap states. At the single-particle level, reversible trapping induces exponential delayed PL and trap PL, with lifetimes ranging from 40 to 1300 ns. In contrast with exciton PL, single-trap PL is broad, shows spectral diffusion, and strictly single-photon emission. Our results highlight the large inhomogeneity of trap states, even at the single-particle level.

15:40 - 15:50
1.4-T2
Ha, Seung Kyun
Massachusetts Institute of Technology (MIT)
Exciton Dynamics in Colloidal 2D Manganese-Doped Hybrid Perovskite Nanoplatelets
Ha, Seung Kyun
Massachusetts Institute of Technology (MIT), US
Authors
Seung Kyun Ha a, Wenbi Shcherbakov-Wu a, b, Eric Powers a, Watcharaphol Paritmongkol a, b, William Tisdale a
Affiliations
a, Department of Chemical Engineering, Massachusetts Institute of Technology
b, Department of Chemistry, Massachusetts Institute of Technology
Abstract

Colloidal lead halide perovskite nanocrystals have emerged as a new class of semiconductors for next-generation technologies. Especially, two-dimensional nanoplatelets exhibit anisotropic dipole moment orientation, strong confinement, and bright emission with high color purity and are considered as one of the leading candidates for a wide range of applications. However, more in-depth studies on metal-doping in those materials are needed for further expansion of the material functionalities and complete understanding of material properties.

In this work, we demonstrate the synthesis of colloidal manganese(Mn2+)-doped organic-inorganic hybrid perovskite nanoplatelets (Chemical formula: L2[ABX3]n-1BX4, L: butylammonium, A: methylammonium or formamidinium, B: lead and manganese, X: bromide, n(=1 or 2): number of PbBr64- octahedral layers in out-of-plane direction) via ligand-assisted reprecipitation method. Substitutional doping of manganese for lead introduces Mn2+ atomic state into the system and the doped nanoplatelets exhibit dual emission coming from the band edge and the dopant state. Interestingly, photoluminescence quantum yield as well as the dual emission intensity of Mn2+-doped perovskite nanoplatelets exhibit strong excitation intensity-dependence. Based on the experimental observations, we propose a kinetic model that describes the dynamics between free excitons and dopant-bound excitons. And by combining the proposed model with time-resolved spectroscopy, we show that exciton-exciton annihilation, not the saturation of Mn2+ atomic states, is responsible for the observed excitation intensity-dependence. Lastly we compare the seemingly distinct band edge-to-dopant exciton transfer rate of methylammonium-based nanopaltelets and formamidinium-based nanoplatelets, and discuss the implications.

15:50 - 16:00
1.4-T3
Marino, Emanuele
University of Pennsylvania
Simultaneous Photonic and Excitonic Coupling in Spherical Quantum Dot Supercrystals
Marino, Emanuele
University of Pennsylvania, US
Authors
Emanuele Marino a, b, Alice Sciortino e, Annemarie Berkhout c, Katherine E. MacArthur d, Marc Heggen d, Tom Gregorkiewicz a, Thomas E. Kodger f, a, Antonio Capretti a, Christopher B. Murray a, A. Femius Koenderink c, Fabrizio Messina e, Peter Schall a
Affiliations
a, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104–6323, USA
b, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands, NL
c, Center for Nanophotonics, AMOLF, The Netherlands, Science Park, 104, Amsterdam, NL
d, Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
e, Dipartimento di Fisica e Chimica−Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
f, Physical Chemistry and Soft Matter, Wageningen University and Research, Stippeneng 4, 6708WE Wageningen, The Netherlands
Abstract

Semiconductor nanocrystals, or quantum dots (QDs), simultaneously benefit from inexpensive low-temperature solution processing and exciting photophysics, making them the ideal candidates for next-generation solar cells and photodetectors. While the working principles of these devices rely on light absorption, QDs intrinsically belong to the Rayleigh regime and display optical behavior limited to electric dipole resonances, resulting in low absorption efficiencies. Increasing the
absorption efficiency of QDs, together with their electronic and excitonic coupling to enhance charge carrier mobility, is therefore of critical importance to enable practical applications. In this talk, I will illustrate a general and scalable approach to increase both light absorption and excitonic coupling of QDs by fabricating hierarchical metamaterials. We assemble QDs into crystalline supraparticles using an emulsion template and demonstrate that these colloidal supercrystals (SCs) exhibit extended resonant optical behavior resulting in an enhancement in absorption efficiency in the visible range of more than 2 orders of magnitude with respect to the case of dispersed QDs. This successful light trapping strategy is complemented by the enhanced excitonic coupling observed in ligand-exchanged SCs, experimentally demonstrated through ultrafast transient absorption spectroscopy and leading to the formation of a free biexciton system on sub-picosecond time scales.[1] These results introduce a colloidal metamaterial designed by self-assembly from the bottom up, simultaneously featuring a combination of nanoscale and mesoscale properties leading to simultaneous photonic and excitonic coupling, therefore presenting the nanocrystal analogue of supramolecular structures.

16:00 - 16:30
Discussion
PERIMPED 1.3
Chair: Beatriz Romero
15:30 - 15:50
1.3-I1
Tilley, David
University of Zurich
Operando Study of Multilayer Water Splitting Photocathodes by Impedance Spectroscopy
Tilley, David
University of Zurich, CH
Authors
Wooseok Yang a, Thomas Moehl a, Erin Service a, David Tilley a
Affiliations
a, University of Zurich, Department of Chemistry, Winterthurerstrasse, 190, Zürich, CH
Abstract

Detailed impedance analysis in photoelectrochemical (PEC) water splitting systems has thus far mainly only been carried out with simple semiconductor-liquid junctions. In this talk, I will discuss our development and evaluation of an impedance model for the more advanced system of a multilayer water splitting photocathode. The initial study comprised an Sb2Se3 photoabsorber coated with a TiO2 layer as a charge-selective contact and finally a RuOx layer as hydrogen evolution catalyst. The different semiconducting layers could be matched to specific elements in the Nyquist plots via the capacitances (e.g. Mott–Schottky plots) and also by the potential dependent behavior of the related resistances. The model was shown to be generalizable for different classes of photoabsorber (Si- and Cu2O-based) under operando conditions. The method we outline can be generally applied to other PEC systems.

15:50 - 16:10
1.3-I2
Ehrler, Bruno
Dependence of Ion Migration on Structural Factors in Metal Halide Perovskites
Ehrler, Bruno
Authors
Bruno Ehrler a
Affiliations
a, Center for Nanophotonics, AMOLF, The Netherlands, Science Park, 104, Amsterdam, NL
Abstract

Ion migration can be harmful to the long-term stability of perovskite solar cells and LEDs. Understanding the properties of mobile ions is the first step in controling them. Here we show how both capacitance-based techniques as well as optical measurements can be used to understand how ion migration depends on composition, grain size and strain.

MAPbBr3 is more stable than MAPbI3 despite very similar structure. We find that MA migration is suppressed in MAPbBr3 and that the halide migration has a higher activation energy.[1] We further find that the Br- migration depends on the grain size, with larger grains showing a larger activation energy.

Halide migration of both I- and Br- is also important for phase segregation in mixed-halide perovskites. We study this phase segregation under hydrostatic pressure and find that the pressure affects both the thermodynamics[2] and kinetics[3] of this phase segregation and hence the halide migration. Phase segregation proceeds more slowly under pressure, and the final phase is more mixed. Finally, we show that the same can be achieved by replacing MA with Cs as the A-site cation. Cs is smaller and hence applies “chemical pressure”.

16:10 - 16:30
1.3-I3
Leite, Marina
University of California, Davis
Functional Imaging of Perovskites' Optical and Electrical Behavior
Leite, Marina
University of California, Davis, US

Marina Leite is an Associate Professor in Materials Science and Engineering at UC Davis. Her group is engaged in fundamental and applied research in hybrid perovskites for optoelectronics, functional imaging of devices through advanced scanning probe microscopy methods, and optical materials. She has delivered >130 invited talks at conferences and research institutions around the globe. Leite is the awardee of the 2016 APS Ovshinsky Sustainable Energy Fellowship from the American Physical Society (APS) and of the 2014 Maryland Academy of Sciences Outstanding Young Scientist Award. Before joining UC Davis, Leite was an Associate Professor at the University of Maryland. She also worked for two years at NIST and was a postdoctoral scholar at Caltech.

Authors
Marina Leite a
Affiliations
a, UC Davis
Abstract

A comprehensive understanding of the effect of the individual and combined effects of extrinsic (humidity and oxygen) and intrinsic (light, bias, and temperature) stressors on halide perovskites is crucial for the ultimate development of stable optoelectronic devices. Here, we present a suite of optical and electrical complementary tools that provide a detailed description of the dynamic responses within these materials. We unfold the 
impact of distinct humidity levels on charge carrier radiative recombination in CsxFA1−xPb(IyBr1−y)3
perovskites through in situ PL, where we temporally and spectrally measure light emission within loops of critical relative humidity (rH) levels. Our results demonstrate that the Cs/Br
 ratio strongly affects the spectral stability of light emission hysteresis, as well as its extent. The photo-emission dynamics in metal halide perovskites with both I and Br is also interrogated by environmental PL, where we find that the presence of Br suppresses hysteresis. We realize a machine learning (ML) approach based on supervised learning combined with environmental PL measurements and determine the (ir)reversible changes that takes place in MAPbBr3 and MAPbI3 model systems, and in state-of-the-art multication compositions such as Cs0.05FA0.79MA0.16Pb(I0.83Br0.17)3 and (Cs0.07Rb0.03FA0.76MA0.14Pb(I0.85Br0.15)3. We further resolve transient processes such as ion motion by spatially resolving the local photovoltage and photocurrent at the nanoscale. Here, we quantify how the addition of Rb reduces the inactivity of the perovskites’ grains. Combined, the macro- and nanoscale environmental measurements performed provide a comprehensive platform for tracking, in real-time, the relevant changes that can lead to degradation. Moreover, they represent a reliable diagnosis tool that can be expanded to any perovskite chemical composition.      

16:30 - 16:50
Discussion
SOLFUL 1.4
Chair not set
15:30 - 15:50
1.4-I1
Mallouk, Thomas
University of Pennsylvania
Managing proton gradients with bipolar membranes in CO2 electrolysis, fuel cells, and redox flow batteries
Mallouk, Thomas
University of Pennsylvania, US

Thomas E. Mallouk received his bachelor’s degree from Brown University and was a Ph.D. student with Neil Bartlett at the University of California, Berkeley. Following postdoctoral work with Mark Wrighton at MIT he held faculty positions at the University of Texas at Austin and at Penn State University.  He is currently Vagelos Professor in Energy Research in the Department of Chemistry at the University of Pennsylvania.  His research focuses on the synthesis of inorganic materials and their application to solar energy conversion, energy storage, catalysis and electrocatalysis, nano- and microscale motors, low dimensional physical phenomena, and environmental remediation.  He is the author of 450+ publications, including a few good ones.  He is a member of the U.S. National Academy of Sciences and the American Academy of Arts and Sciences, and a Fellow of the American Chemical Society.

Authors
Zhifei Yan a, Jeremy Hitt a, Zichen Zeng a, Langqiu Xiao a, Yein Yoon a, Ryszard Wycisk b, Peter Pintauro b, Thomas Mallouk a
Affiliations
a, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104–6323, USA
b, Department of Chemical and Biomolecular Engineering, Vanderbilt University
Abstract

In studying water splitting with dye-sensitized solar cells, we discovered a system-level problem that arises when the cells are operated near neutral pH. In buffer-based water splitting cells, losses from solution resistance and electrochemically generated pH gradients become substantial over a timescale of hours.  This problem can be addressed by using bipolar membrane-based cells in which the cathode and anode operate at low and high pH, respectively.  Bipolar membranes enable efficient water splitting and CO2 electrolysis, and are also interesting for other membrane-based electrochemical energy conversion devices such as fuel cells and redox flow batteries.  The  reaction enabling these applications is water association/dissociation at the bipolar polymer interface, for which catalysis is essential but still not fully understood.

15:50 - 16:10
1.4-I2
Atwater, Harry
California Institute of Technology
The Direct Solar Liquid Fuels Challenge
Atwater, Harry
California Institute of Technology, US

Harry Atwater is the Howard Hughes Professor of Applied Physics and Materials Science at the California Institute of Technology. Atwater’s scientific interests span light-matter interactions from quantum nanophotonics, two-dimensional materials and metasurfaces to solar photovoltaics and artificial photosynthesis. Atwater is an early pioneer in nanophotonics and plasmonics; he gave the name to the field of plasmonics in 2001. He currently serves as Director of the Liquid Sunlight Alliance, a DOE Solar Fuels Hub project, and was the founding Director of the Resnick Sustainability Institute at Caltech. He also chairs the Breakthrough Starshot Lightsail Committee and is a PI of the Caltech Space Solar Power Project.

Atwater has laid the foundations for plasmonic and negative index metamaterials, as well as tunable nanophotonic materials and metasurfaces. He has pioneered principles for light management and high efficiency solar cell design.  He was the co-founder of Alta Devices, a solar photovoltaics company in Santa Clara, CA that holds the current world records for 1 Sun single and dual junction solar cell efficiency as well as solar module efficiency.

As of October 2020, he has authored or co-authored more than 500 publications and 60 patents cited in aggregate > 70,000 times and marked by citation metrics: h index = 95 (Web of Science) and h = 118 (Google Scholar), and he is an ISI Highly Cited Researcher (2014-2019). His group’s advances in the solar energy and plasmonics field have been reported in Scientific American, Science, Nature Materials, Nature Photonics and Advanced Materials.

Harry Atwater is a Member of US National Academy of Engineering and is also a Fellow of the American Physical Society, the Materials Research Society, SPIE and the National Academy of Inventors.  Atwater has been honored by awards including: Kavli Innovations in Chemistry Lecture Award, American Chemical Society (2018); APS David Adler Lectureship for Advances in Materials Physics (2016); Julius Springer Prize in Applied Physics (2014); Fellowship from the Royal Netherlands Academy of Arts and Sciences (2013); ENI Prize for Renewable and Nonconventional Energy (2012); SPIE Green Photonics Award (2012); MRS Kavli Lecturer in Nanoscience (2010); and the Popular Mechanics Breakthrough Award (2010). He also received the Joop Los Fellowship from the Dutch Society for Fundamental Research on Matter (2005), the A.T.&T. Foundation Award (1990), the NSF Presidential Young Investigator Award (1989) and the IBM Faculty Development Award in 1989-1990.

He is the founding Editor in Chief for the journal ACS Photonics, and is Associate Editor for the IEEE Journal of Photovoltaics. In 2006 he founded the Gordon Research Conference on Plasmonics, for which he served as chair in 2008.  Professor Atwater has worked extensively as a consultant for industry and government and has actively served the materials community in a variety of roles, including President of the Materials Research Society in 2000, MRS Meeting Chair in 1997, and a member of the Board of Trustees of the Gordon Research Conferences. He also teaches graduate level Applied Physics classes at Caltech in nanophotonics, solid-state physics and device physics.

Professor Atwater received his B. S., M. S. and Ph.D. degrees from the Massachusetts Institute of Technology in 1981, 1983 and 1987, respectively. He held the IBM Postdoctoral Fellowship at Harvard University from 1987-88 and has been a member of the Caltech faculty since 1988.

Authors
Harry Atwater a, b
Affiliations
a, Liquid Sunlight Alliance, California Institute of Technology
b, Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, CA, USA, US
Abstract

The Liquid Sunlight Alliance (LiSA) is embracing the challenge of direct synthesis of solar liquid fuels, and the new science of co-design of solar fuels systems as assemblies of chemical microenvironments. This powerful approach enables the coupling of microenvironments to achieve more complex products via gradients in temperature and pH, as well as fluxes of protons, electrons, reactants, and intermediates, thereby setting up sequential catalytic steps and tailoring the chemical landscape for each step.

Until now, science advances in solar fuels have largely centered on answering mechanistic questions related to unit processes, such as reactions in the thermodynamic and kinetic landscape around a catalytic center, or charge carrier generation and transport. Previously, the science has also largely concentrated on processes occurring in a single sunlight-driven microenvironment such as a photoabsorber-catalyst interface. Such approaches have sufficed to establish the science for generation of gaseous fuel products such as molecular hydrogen or carbon monoxide, where small numbers of electron and proton transfers are needed. Moreover, most solar fuels science has addressed conditions where pure feedstocks are present, such as liquid water as a source for hydrogen generation, or carbon dioxide as a source for generation of reduced products of CO2. However, the ultimate goal of direct solar generation of liquid fuels, such as multicarbon reduced products of carbon dioxide, using impure sources is a far greater challenge that requires a conceptually different approach. To control the complex interplay of sequential or coupled transfers of multiple electrons, protons, and photons needed for liquid solar fuels, requires a re-thinking of the microenvironments that bring reactants to the reaction center. We expect that assemblies of chemical microenvironments for artificial photosynthesis will exhibit characteristics similar to natural photosynthetic systems, where different environments within the an integrated system perform separate functions (light harvesting, photosynthetic reactions to generate reductants, and dark reactions for fixation of carbon dioxide) and regulatory mechanisms that govern the coupling among them. Unlike natural photosynthesis, artificial photosynthesis also allows us to explore uses of light beyond charge carrier generation. Accordingly, LiSA is investigating use of light-driven phenomena to induce catalytic selectivity, to control local pH, to activate molecular transport, and to drive solar thermal catalytic processes.   I will describe several of LiSA's directions for direct solar-driven synthesis of liquid fuels that address challenges of selectivity, efficinecy and durability for solar fuels systems.

16:10 - 16:30
1.4-I3
Frei, Heinz
Optimizing Electron and Proton Transport across Ultrathin Separation Membrane for Artificial Photosynthesis
Frei, Heinz
Authors
Heinz Frei a
Affiliations
a, Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
Abstract

Inspired by the design of natural photosynthesis, which is the only existing system to make chemical compounds on the terawatt scale, we are developing an artificial photosystem in which the most demanding charge transfer and catalytic transformations are accomplished on the shortest possible length scale - nanometers - under membrane separation. Implemented as Co3O4-SiO2 core-shell nanotubes arranged in the form of square inch-sized arrays, the design affords extension of the favorable properties of the nanotubes, each constituting an independently operating complete photosynthetic unit, to the macroscale. An essential part of the nanotube is a 3 nm thick amorphous silica membrane with embedded molecular wires that chemically separates the incompatible CO2 reduction and H2O oxidation environments while providing electronic and protonic communication between them. The ultrathin membrane minimizes large resistance losses caused by ion transport across macroscale distances and avoids efficiency-degrading back and side reactions.

Electron transfer from light absorber across the SiO2 nanomembrane to Co3O4 water oxidation catalyst was evaluated by photocurrent measurements using planar analogues of the core-shell nanotube wall assembled by ALD. For efficient directional charge transfer, the density of embedded molecular wires (oligo(p-phenylenevinylene), 3 aryl units) is quantitatively assessed by polarized FT-IRRAS and found to affect the photocurrent in linear fashion. Most critical is the energy level alignment of the wires with the visible light absorber on one side and the Co3O4 catalyst on the opposite side of the membrane. A steep dependence of the charge flux on the HOMO potential of the wire is uncovered by photocurrent measurements for wires whose potential was varied by using electron donating or withdrawing substituents. While the amorphous SiO2 membrane accomplishes directionally controlled charge transfer and blocks crossover of O2 and other small molecules, EIS uncovered far higher proton flux through the stacked multi-oxide nanowall than required even at highest solar intensity. This is due to a large H+ flux boosting effect of the ultrathin SiO2 layer sandwiched between metal oxide nanolayers, which is enabled by interfacial covalent O bridges identified by FT-IRRAS that provide fast H+ hopping pathways across the solid-solid interfaces.

The work demonstrates that inert silica nanolayers with embedded molecular wires offer a conducting ultrathin separation membrane with unprecedented ability to fine-tune charge transfer directionality and rates, high proton permeability, and chemical separation of small molecules. These properties enable artificial photosynthetic units that accomplish the complete cycle on the nanoscale.

 

16:30 - 16:50
Discussion
TINPERO 1.3
Chair not set
15:30 - 15:50
1.3-I1
Loi, Maria Antonietta
University of Groningen, The Netherlands
Field effect transistors as a tool to understand FASnI3
Loi, Maria Antonietta
University of Groningen, The Netherlands, NL

Maria Antonietta Loi studied physics at the University of Cagliari in Italy where she received the PhD in 2001. In the same year she joined the Linz Institute for Organic Solar cells, of the University of Linz, Austria as a post doctoral fellow. Later she worked as researcher at the Institute for Nanostructured Materials of the Italian National Research Council in Bologna Italy. In 2006 she became assistant professor and Rosalind Franklin Fellow at the Zernike Institute for Advanced Materials of the University of Groningen, The Netherlands. She is now full professor in the same institution and chair of the Photophysics and OptoElectronics group. She has published more than 130 peer review articles in photophysics and optoelectronics of nanomaterials. In 2012 she has received an ERC starting grant.

Authors
Maria Antonietta Loi a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Abstract

In one of our recent works, we successfully reduced the p‐doping level (hole density) in 3D formamidinium tin triiodide (FASnI3) perovskite of more than one order of magnitude by incorporating a small amount of the 2D Ruddlesden-Popper (R-P) tin perovskite. The addition of the R–P phase enhances enormously the crystallinity and the orientation of the 3D phase. The highly ordered 3D phase is potentially very interesting for its application as an active layer in FETs. This gives us the motivation to investigate its charge‐transport properties. We fabricated reference FETs, which use pure 3D tin perovskite film as the semiconducting channel, in bottom‐gate bottom‐electrode configuration, with SiO2 as the dielectric material. These devices, as expected, failed to show field‐modulated charge transport due to high density of holes (5.8 × 1017 cm−3) in the channel. Conversely, the FETs using the 2D/3D perovskite semiconducting channel show field‐induced p‐type conduction in the same device geometry due to the reduced hole carrier density (1016 cm−3). The FET using a 48 nm thick 2D/3D layer shows a hole mobility extracted from the linear region of 0.12 cm2 V−1 s−1 and a threshold voltage (VTH) of 28 V. Compared to the FET based on 2D/3D, the FET based on pure 2D R–P layer shows an inferior hole mobility in the order of 10−3 cm2 V−1 s−1 due to the combined quantum‐ and dielectric‐confinement effects and larger injection barrier at the perovskite/bottom‐electrode interface. An improved device structure, using Al2O3 as the top‐gate dielectric, allows us to reduce significantly the VTH to 2.8 V as a direct consequence of the oxide high capacitance. Moreover, in this optimized device geometry, the hole mobility is increased up to 0.21 cm2 V−1 s−1 with an ION/OFF ratio of 104. Interestingly, these devices show mostly improved performances after 20 months of storage in N2 atmosphere.

15:50 - 16:10
1.3-I2
Petrozza, Annamaria
CompuNet, Istituto Italiano di Tecnologia (IIT), Genova
Defects in Tin-Halide Perovskite Semiconductors
Petrozza, Annamaria
CompuNet, Istituto Italiano di Tecnologia (IIT), Genova, IT

Annamaria Petrozza received her PhD in Physics from the University of Cambridge (UK) in 2008 with a thesis on the study of optoelectronic processes at organic and hybrid semiconductors interfaces under the supervision of Dr. J.S. Kim and Prof Sir R.H. Friend. From July 2008 to December 2009 she worked as research scientist at the Sharp Laboratories of Europe, Ltd on the development of new market competitive solar cell technologies (Dye Sensitized Solar cells/Colloidal Quantum Dots Sensitized Solar cells). Since January 2010 she has a Team Leader position at the Center for Nano Science and Technology -IIT@POLIMI. She is in charge of the development of photovoltaic devices and their characterization by time-resolved and cw Photoinduced Absorption Spectroscopy, Time-resolved Photoluminescence and electrical measurements. Her research work mainly aims to shed light on interfacial optoelectronic mechanisms, which are fundamental for the optimization of operational processes, with the goal of improving device efficiency and stability.

Authors
Annamaria Petrozza a
Affiliations
a, Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, via Giovanni Pascoli 70/3, 20133, Milan, Italy
Abstract

I will summarize our understanding of the nature of defects and their photo-chemistry in tin-halide perovskites thin films. We show that, in inert conditions, tin, p-doped, and lead (intrinsic) based perovskite thin film show comparable photoluminescence quantum yield, at comparable morphology. The thin film is also extremely stable under light soaking.  On the other hand, photovoltaic devices, showing comparable device architecture show a dramatic reduction in power conversion efficiency for tin based devices. While so far, most of the community effort has been focused on the optimization of the perovskite thin film, very little work has been done on the design of the solar cell architecture. Here we will show new architectures for making tin based solar cells a competitive solution.

16:10 - 16:30
1.3-I3
Mundt, Laura E.
SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, USA
Surface Degradation Chemistry in Mixed Tin-Lead Halide Perovskite Solar Cells
Mundt, Laura E.
SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, USA, US
Authors
Laura E. Mundt a, Jinhui Tong b, Axel F. Palmstrom b, Sean P. Dunfield b, Kai Zhu b, Joseph J. Berry b, Laura S. Schelhas b, Erin L. Ratcliff c
Affiliations
a, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, USA, US
b, National Renewable Energy Laboratory, Golden, Colorado, 1617 Cole Boulevard, Golden, Colorado, 80401, US
c, University of Arizona, 1133 E. James E Rogers Way, Tucson, US
Abstract

Driven by the desire to manufacture low-cost, high-efficient, flexible and light weight solar cells, all-metal halide perovskite tandem solar cells are a strong competitor in the race for next-generation photovoltaics. To achieve a suitable low band gap for bottom cells in an all-perovskite tandem device, the metal cation in the ABX3 perovskite can be partially substituted by tin. While these mixed tin−lead halide perovskite solar cells have promising power conversion efficiencies, long-term stability remains a challenge on the way to commercialization [1]. Recently, several approaches have been reported to mitigate the degradation in low band gap tin – lead devices either by mitigating the detrimental oxidation of Sn2+ to Sn4+ via limiting the tin content [2] or using multifunctional solvent additives [3], or by optimizing the adjacent charge transport layers [4]. While these results are very encouraging and demonstrate pathways to engineer around potential instabilities, additional fundamental insights into degradation pathways in these material systems are crucial to inform the design of stable, high-efficiency low band gap perovskite solar cells. Here, we present a study on tin−lead perovskite devices, with 60:40 tin to lead ratio, to better understand diminished device performance upon thermal treatment, both in ambient and inert atmosphere [5]. Probing the crystal structure under operational conditions shows a stable bulk structure of the perovskite absorber, suggesting that the degradation mechanism is dominated by the surface chemistry. X-ray photoelectron spectroscopy supports this hypothesis and reveals new observations: first, we find that even pristine samples show an oxygen-rich surface, suggesting that surface-adsorbed oxygen is likely present at the numerous interfaces in a metal halide perovskite solar cell. Further, in addition to the previously reported Sn4+ evolution, we observe the formation of I3- intermediates preceding I2 loss at the surface and) evidence of under-coordinated tin and lead surface sites (Snδ<2+ and Pb δ<2+, respectively) in inert and ambient conditions. The evidence of both oxidized and reduced species indicates an activated corrosion mechanism at the surface as a possible chemical degradation pathway. Though we expect that these processes cannot be fully circumvented, we find that the understanding of the fundamental redox chemistry is crucial to inform the rational design of interfaces in these devices to mitigate this degradation pathway.

16:30 - 16:55
Discussion
16:55 - 17:00
TINPERO Closing
17:00 - 18:30
ePoster Session
 
Wed Mar 10 2021
10:30 - 10:35
NanoLight Opening nanoGe
10:30 - 10:35
PERIMPED Opening nanoGe
10:35 - 10:45
NanoLight Session Introduction 2.1 Alexander Urban
10:35 - 10:45
PERIMPED Session Introduction 2.1
NanoLigh 2.1
Chair: Alexander Urban
10:45 - 11:05
2.1-I1
Uller Rothmann, Mathias
University of Oxford
The atomic-scale microstructure of metal halide perovskite elucidated via low-dose electron microscopy
Uller Rothmann, Mathias
University of Oxford, GB
Authors
Mathias Uller Rothmann a, b, Judy Kim b, c, d, Juliane Borchert a, Kilian Lohmann a, Alex Sheader b, Colum O'Leary b, Laura Clark b, Michael Johnston a, Henry Snaith a, Peter Nellist b, Laura Herz a
Affiliations
a, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, GB
b, Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH
c, ePSIC, Diamond Light Source
d, Rosalind Franklin Institute
Abstract

Studying the crystallographic properties of these photoactive hybrid perovskites by transmission electron microscopy (TEM) has proved particularly challenging due to the large electron energies typically employed in these studies.[1] In particular, the very close structural relationship between a number of crystallographic orientations of the pristine perovskite and lead iodide has resulted in severe ambiguity in the interpretation of EM-derived information, severely impeding the advance of atomic resolution understanding of the materials.

Here, we successfully image the archetypal CH(NH2)2PbI3 (FAPbI3) and CH3NH3PbI3 (MAPbI3­) hybrid perovskites in their thin-film form with atomic resolution using a carefully developed protocol of low-dose STEM.[2] Our images enable a wide range previously undescribed phenomena to be observed, including a remarkably highly ordered atomic arrangement of sharp grain boundaries and coherent perovskite/PbI2 interfaces, with a striking absence of long-range disorder in the crystal. These findings explain why inter-grain interfaces are not necessarily detrimental to perovskite solar cell performance, in contrast to what is commonly observed for other polycrystalline semiconductors. Additionally, we observe aligned point defects and dislocations that we identify to be climb-dissociated, and confirm the room-temperature phase of CH(NH2)2PbI3 to be cubic. We further demonstrate that degradation of the perovskite under electron irradiation leads to an initial loss of CH(NH2)2+ ions, leaving behind a partially unoccupied, but structurally intact, perovskite lattice, explaining the unusual regenerative properties of partly degraded perovskite films. Our findings thus provide a significant shift in our atomic-level understanding of this technologically important class of lead-halide perovskites.

11:05 - 11:25
2.1-I2
Scheblykin, Ivan
Lund University, Department of Chemical Physics and NanoLund, Sweden
Are Shockley-Read-Hall and ABC Models Valid for Lead Halide Perovskites?
Scheblykin, Ivan
Lund University, Department of Chemical Physics and NanoLund, Sweden, SE

Ivan Scheblykin obtained Ph.D. in 1999 from Moscow Institute of Physics and Technology and Lebedev Physical Institute of Russian Academy of Sciences on exciton dynamics in J-aggregates. After a postdoctoral stay in the KU Leuven, Belgium, he moved to Sweden to start the single molecule spectroscopy group at the Division of Chemical Physics in Lund University where he became a full professor in 2014. His interests cover fundamental photophysics of organic and inorganic semiconductors and, in particular, energy transfer, charge migration and trapping. The general direction of his research is to comprehend fundamental physical and chemical processes beyond ensemble averaging in material science and chemical physics using techniques inspired by single molecule fluorescence spectroscopy and single particle imaging.

Authors
Alexander Kiligaridis a, Pavel Frantsuzov c, Aymen Yangui a, Sudipta Seth Sudipta Seth a, Jun Li Jun Li a, Qingzhi An Qingzhi An b, Yana Vaynzof Yana Vaynzof b, Ivan Scheblykin a
Affiliations
a, Lund University, Department of Chemical Physics, Getingevägen 60, Lund, 22241, SE
b, Technical University (TU) Dresden, Mommsenstr. 13, Dresden, 1062, DE
c, Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Novosibirsk, Russia
Abstract

Charge dynamics in metal halide perovskites is poorly understood due to limited knowledge of defect physics, charge recombination mechanisms and photo-induced instability of the materials properties. Nevertheless, classical ABC and Shockley-Read-Hall (SRH) models are ubiquitously applied to perovskites without considering their validity. We examined the validity of the commonly employed ABC and SRH kinetic models in describing the charge dynamics of metal halide perovskite MAPbI3 semiconductor. For this purpose, we developed a novel experimental methodology based on PL measurements (PLQY and time resolved decays) performed in the two-dimensional space of the excitation energy and the repetition frequency of the laser pulses. We scan the repetition frequency from 100 Hz to 80 MHz and the pulse fluence from 108 to 1012 photons/cm3. The measured PLQY maps which shape reminds a “horse with a mane” (see the picture) allow for an unmistakable distinction between samples, and more importantly, between the single-pulse and quasi-continuous excitation regimes.

We found that neither ABC nor SRH model can explain the complete PLQY maps for MAPbI3 samples and predict the PL decays at the same time. Each model is valid only in a limited range of parameters, which may strongly vary between different samples. On the other hand, we show that the extension of the SRH model by the addition of Auger recombination and Auger trapping (SRH+ model) results in an excellent fit of the complete PLQY maps for all the studied samples. Nevertheless, even this extended model systematically underestimate the PL decay rates at high pulse fluences pointing towards the existence of additional processes in MAPbI3 which must be considered to fully explain the charge carrier dynamics.

Our study clearly shows that neither PL decay nor PLQY data alone are sufficient to elucidate the photophysical processes in perovskite semiconductors. Instead, a combined PLQY mapping and time-resolved PL decays should be used to elucidate the excitation dynamics and energy loss mechanisms in luminescent semiconductors. Our experimental approach provides a strict criteria for testing any theoretic model of charge dynamics which is the requirement to be able to fit PLQY(f,P) map and PL decays at different powers and pulse repetition rates.

11:25 - 11:45
2.1-I3
Plochocka, Paulina
Laboratoire National des Champs Magnétiques Intenses, CNRS
Energy and charge transfer in hybrid transition metal dichalcogenide/2D perovskite heterostructures
Plochocka, Paulina
Laboratoire National des Champs Magnétiques Intenses, CNRS, FR

Paulina Plochocka, Directrice de recherché de 2e classe (DR2) in Laboratoire National des Champs Magnétiques Intenses (LNCMI), CNRS in Toulouse.

P. Plochocka obtained her PhD cum-laude in 2004 at the University of Warsaw working on the dynamics of many-body interactions between carriers in doped semi-magnetic quantum wells (QW). During her first post doc at Weizmann Institute of science, she started working on the electronic properties of a high mobility 2D electron gas in the fractional and integer quantum Hall Effect regime. She continued this topic during second post doc in LNCMI Grenoble, where she was holding individual Marie Curie scholarship. At the same time, she enlarged her interest of 2D materials towards graphene and other layered materials as TMDCs or black phosphorus. In 2012 she obtained permanent position in LNCMI Toulouse, where she created the Quantum Electronics group, which investigates the electronic and optical properties of emerging materials under extreme conditions of high magnetic field and low temperatures. Examples include semiconducting layer materials such as transition metal dichalcogenides, GaAs/AlAs core shell nanowires and organic inorganic hybrid perovskites.

Authors
Paulina Plochocka a, b
Affiliations
a, Laboratoire National des Champs Magnétiques Intenses, CNRS, Avenue de Rangueil, 143, Toulouse, FR
b, Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
Abstract

Van  der  Waals  heterostructures  are  currently the focus of intense investigation, essential due to the unprecedented flexibility offered by the total  relaxation  of  lattice  matching  requirements, and their new and exotic properties compared to the  individual  layers.  I will discuss the properties of the hybrid  transition  metal  dichalcogenide/2D  perovskite  heterostructure, for example  WS2/(PEA)2PbI4.   I will show the  first  DFT  calculations  of  a  heterostructure   ensemble,   which   reveal   a   novel band  alignment,  where  direct  electron  transfer is  blocked  by  the  organic  spacer  of  the  2D  perovskite.    In  contrast,  the  valence  band  forms a  cascade  from  WS2 through  the  PEA  to  thePbI4layer allowing hole transfer.  These predictions are supported by optical spectroscopy studies, which provide compelling evidence for both charge  transfer,  and  nonradiative  transfer  of the excitation (energy transfer) between the layers.  Our results show that TMDs/2D perovskite heterostructures  provide  a  flexible  and  convenient way to engineer the band alignment.

11:45 - 12:05
Discussion
PERIMPED 2.1
Chair: Pablo P. Boix
10:45 - 11:05
2.1-I1
Ravishankar, Sandheep
Forschungszentrum Jülich, Institute of Energy and Climate Research, IEK-5 Photovoltaics
A Multilayer Model to Understand the Capacitance Response of Perovskite Solar Cells
Ravishankar, Sandheep
Forschungszentrum Jülich, Institute of Energy and Climate Research, IEK-5 Photovoltaics, DE

Sandheep Ravishankar completed his PhD on the electrical modelling of physical mechanisms of operation of perovskite solar cells at the institute of advanced materials (INAM), Universitat Jaume I, Castellon, Spain. He is currently a researcher at IEK-5, Forschungszentrum Juelich, Germany, in the department of analytics and simulation. His primary research interest is the characterization of loss mechanisms in perovskite solar cells using a mixture of capacitance and luminescence-based techniques, supplemented by simulations. His secondary research interest is the characterization of kinetics and physical processes occurring in photoelectrochemical devices for water splitting.

Authors
Sandheep Ravishankar a, Thomas Kirchartz a
Affiliations
a, IEK-5 Photovoltaik, Forschungszentrum Jülich GmbH, Germany, 52425 Jülich, DE
Abstract

Capacitance measurements are useful tools to identify relevant parameters that strongly affect the physics of operation of a solar cell, such as doping densities, trap densities and trap activation energies. However, their direct application to perovskite solar cells can yield several erroneous results, even though they appear intuitively correct. In this talk, I will explain the reasoning behind this claim by developing a fundamental capacitance model that involves transitions between the geometric capacitances of the different layers comprising the perovskite solar cell. This multilayer capacitance model, combined with charge injection, serves a base model for a solar cell with an intrinsic absorber and provides a minimum response that will be observed in capacitance-voltage-frequency-temperature measurements, that is often mistaken as characteristic signals of other physical processes. The acknowledgement of these limits will allow discrimination between different capacitive processes in a more effective manner and help better understand the capacitance response of the perovskite solar cell.

11:05 - 11:25
2.1-I2
Mora-Seró, Iván
From Dye Sensitized to Perovskite Solar Cells, The Missing Link in the Impedance Equivalent Circuit
Mora-Seró, Iván
Authors
Iván Mora-Seró a
Affiliations
a, Institute of Advanced Materials (INAM), University Jaume I, Avenida de Vicent Sos Baynat, s/n, 12071 Castelló de la Plana, Spain
Abstract

Impedance spectroscopy (IS) has been key to characterize the main physical processes governing the behavior of dye and quantum dot sensitized solar cells, which are considered, in many aspects, perovskite solar cells predecessor. However, while the interpretation of the impedance pattern of dye sensitized solar cells is clearly established, in contrast, IS application to perovskite-based devices generates uncommon features and misleading outputs, mainly due to the lack of a stablished model for the results interpretation. We have analyzed how perovskite sensitized solar cells evolve to standard perovskite solar cells studying their impedance pattern. This transition is characterized by a change in the working principles, determined by an evolution of the dominant capacitance: from the intermediate frequency chemical capacitance of TiO2 in devices with isolated perovskite domains, to a large low-frequency capacitance which divides the spectra in two sections. This study gives access to the characteristic features of the system, which we leverage to provide a rationalized IS model with the focus on transport and recombination processes. The model, by means of an AC branch, paves the way to study the material and interfacial properties distinctive of perovskite solar cells. Concurrently, it provides the distribution of transport-related and recombination-related losses, a crucial tool for further development of perovskite photovoltaics. We also show the application of this model in different cases.

11:25 - 11:45
Discussion
11:30 - 11:35
SOLFUL Opening nanoGe
SOLFUL 2.1
Chair not set
11:35 - 11:45
2.1-T1
Rahaman, Motiar
University of Cambridge, Department of Chemistry
Solar CO Production from Aqueous CO2 by Integrating a Cu96In4 Catalyst into a Bias-free Perovskite–BiVO4 Tandem Device
Rahaman, Motiar
University of Cambridge, Department of Chemistry, GB
Authors
Motiar Rahaman a, Virgil Andrei a, Chanon Pornrungroj a, Demelza Wright a, b, Jeremy J Baumberg b, Erwin Reisner a
Affiliations
a, Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
b, Cavendish Laboratory, Department of Physics, University of Cambridge, UK, JJ Thomson Avenue, Cambridge, GB
Abstract

Solar-driven fuel synthesis is attracting great attention now-a-days as it opens up the possibility to convert the greenhouse gas CO2 into renewable fuels where solar energy is stored as chemical energy. Despite recent advancements in solar fuel research, design of selective catalyst materials and assembly of unassisted solar devices for efficient CO2-to-fuel conversion still remains challenging. Here, we demonstrate a novel approach of integrating an inexpensive Cu96In4 transition metal alloy catalyst into a state-of-the-art lead halide triple cation perovskite–BiVO4 tandem device for bias-free solar CO production from aqueous CO2. The Cu96In4 alloy catalyst, synthesized by a template-assisted electrodeposition method, has a unique 3D dendritic morphology and it shows excellent electrocatalytic activity towards selective CO production at low overpotentials (>70% CO selectivity at –0.3 V vs. reversible hydrogen electrode (RHE)). A weaker *CO adsorption on the Cu96In4 alloy surface compared to pristine Cu was observed by operando Raman spectroscopy which supports the immediate release of CO as gaseous product from the alloy surface. The BiVO4ǁperovskite׀Cu96In4 tandem device shows an excellent ~75% selectivity towards solar CO production from aqueous CO2 under bias-free conditions where the solar-to-CO conversion efficiency reached 0.19% after 10 h operation. Furthermore, the perovskite׀Cu96In4 cathode shows robust and unaltered photoelectrochemical activity under different light intensities which indicates that the device can be used under varying daylight conditions or even on a cloudy day with diffused sunlight

11:45 - 11:55
2.1-T2
Guzmán, Hilmar
Polytechnic of Turin
Electrocatalytic CO2 Reduction on CuZnAl-based Oxide Catalysts: Tuning of the H2/CO Ratio
Guzmán, Hilmar
Polytechnic of Turin, IT

Hilmar Guzmán is 29 years old. She is Venezuelan. She has completed her master’s degree and bachelor’s degree at Politecnico di Torino (Italy), in the framework of a double degree between Politecnico di Torino (Italy) and Universidad Central de Venezuela (Venezuela). She is currently in the third year of her PhD course, which is focused on the conversion of CO2 through an electrocatalytic route. She does her job with professionalism and responsibility, respecting the time needed to deliver the work and demonstrating problem-solving skills.

Authors
Hilmar Guzmán a, Daniela Roldán a, Adriano Sacco b, Micaela Castellino a, Marco Fontana b, Nunzio Russo a, Simelys Hernández a, b
Affiliations
a, CREST group, Department of applied science and technology (DISAT), Politecnico di Torino, C.so Duca degli Abruzzi, 24, 10129, Turin, Italy.
b, Center for Sustainable Future Technologies, IIT@Polito, Istituto Italiano di Tecnologia, Via Livorno, 60, 10144, Turin, Italy.
Abstract

Electrochemical Reduction of CO2 (ER-CO2) is a very attractive alternative to tackle Global Warming.[1] Cu-based materials have shown increased hydrocarbon and oxygenate production yields, while its selectivity towards CO is low. Inspired by the thermocatalytic process, a traditional co-precipitation method was employed to synthesize CuZnAl-based oxide catalysts with a mesoporous structure. This CuZnAl catalyst was tested for the first time for the ER-CO2 under ambient conditions.[2] The chemical-physical properties of the catalysts were studied by several characterization techniques (e.g. XRD, XPS, BET, SEM, TEM) and electrochemical impedance spectroscopy at different applied-potentials to understand the role of the modification of the catalyst components during operation in the final selectivity and activity. Results revealed that adding amphoteric metal oxides like ZnO and Al2O3 to the CuO-based catalyst contributed to promote CO formation over H2. XPS measurements on the fresh samples revealed that the ternary CuZnAl catalyst presented a lower percentage (5%) of Cu0 + Cu1+ mixture on the surface than the other catalysts, being mainly constituted by Cu+2. This material reached a Faradaic efficiency towards syngas of almost 95% at -0.89 V vs RHE. Nevertheless, the highest production rate of syngas was obtained at the most negative applied potential (⁓ 17 µmol h-1 cm-2 at -1.14 V vs RHE).). A tunable H2/CO ratio was achieved by applying different potentials, reaching lower values by increasing applied negative potential (CO current density increased). In fact, a syngas with a H2/CO ratio of ⁓ 2 was obtained at -1.39 V vs RHE (see Fig. 1), which is a suitable raw material for further methanol synthesis.[3] The enhanced performance for syngas production of the developed CuZnAl catalyst is demonstrated to be attributed to its surface properties (i.e. alkalinity and the oxidation state on the surface, its lowest diffusional mass transfer resistance, its highest total pore volume and the lowest Cu crystals size among the prepared catalysts.

11:55 - 12:05
2.1-T3
Vijay, Sudarshan
Technical University of Denmark (DTU)
Unified model of CO2R to CO on transition metal and supported single atom catalysts: Role of dipole-field interactions
Vijay, Sudarshan
Technical University of Denmark (DTU), DK
Authors
Sudarshan Vijay a, Wen Ju b, Georg Kastlunger a, Peter Strasser b, Karen Chan a
Affiliations
a, Technical University of Denmark, Department of Physics, Fysikvej, 312, Kongens Lyngby, DK
b, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, Berlin 10623, Germany.
Abstract

Carbon based 2D catalysts hold great promise for electrochemical CO2 reduction [1] . However, modelling these materials in an electrochemical environment presents several open challenges. Prime among them is determining ab-initio energetics at constant driving force [2]. We propose a simple methodology that can be readily used to simulate dipole-field interactions for CO2R intermediates accurately and at minimal computational cost. Using this approach, we show that these dipole-field interactions dictate the rate limiting step for CO2R to CO. Based on potential dependent energetics, we develop a simple design principle to predict which step in this reaction network is rate limiting on a given material. We validate our computational approach by pH dependent measurements which shows the efficacy of our descriptors in the mechanistic understanding of CO2R.

12:05 - 12:15
Abstract not programmed
12:15 - 12:45
Discussion
11:40 - 11:45
CHEMNC Opening nanoGe
CHEMNC 2.1
Chair: Jonathan De Roo
11:45 - 11:55
2.1-T1
LHUILLIER, EMMANUEL
Seeded growth of HgTe nanocrystals for shape control and their use in narrow infrared electroluminescence
LHUILLIER, EMMANUEL
Authors
EMMANUEL LHUILLIER a
Affiliations
a, INSP, Institut des Nanosciences de Paris, Sorbonne Université, CNRS
Abstract

HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectronics. Despite their cubic zinc blende lattice, HgTe NCs tend to grow in a multipodic fashion, leading to poor shape and size control. Strategies to obtain HgTe NCs with well-controlled sizes and shapes remain limited and sometimes challenging to handle, increasing the need for a new growth process. Here, we explore a synthetic route via seeded growth. In this approach, the small HgTe seeds are nucleated in the first step, and they show narrow and bright photoluminescence with 75% quantum yield in the near infrared region. Once integrated into Light emitting diodes (LEDs), these seeds lead to devices with high radiance up to 20 W×Sr-1×m-2 for an emission around 1400nm and a long lifetime. Heating HgTe seeds formed at the early stage leads to the formation of sphere-shaped HgTe with tunable band edges from 2 to 4 µm. Last, the electronic transport tests conducted on sphere-shaped HgTe NC arrays reveals enhanced mobility and stronger temperature dependence than the multipodic shaped particles.

11:55 - 12:05
2.1-T2
Dong, Jingjin
Improving the Thermoelectric Properties of PEDOT:PSS Thin Films by Incorporation of Spark Discharge Generated Tin Oxide Nanoparticles
Dong, Jingjin
Authors
Giuseppe Portale a, Jingjin Dong a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Abstract

Poly(3,4-ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS) exhibits valuable characteristics concerning stability, green-processing, flexibility, high electrical conductivity and ease of property modulation, qualifying it as one of the most promising p-type organic conductors for flexible electronic and thermoelectric applications. While blending with inorganic counterparts is considered as a good strategy to further improve polymeric TE properties, only few attempts have been successful so far, due to difficulties to obtain homogeneous embedding and to the non-ideal contact between the organic and inorganic components. Here we propose a new strategy to include nanoparticles without any ligand termination inside PEDOT:PSS thin films. Spark discharge-generated tin oxide nanoparticles (SnOx-NPs) are "gently" and homogenously deposited onto the film through low-energy diffusion mode. Grazing incidence wide angle X-ray scattering and X-ray photoelectron spectroscopy suggest strong PSS/SnOx-NPs interaction in the topmost layer, causing structural reorganization towards an improved PEDOT chains crystalline packing leading to higher carrier mobility. At the same time, dedoping and energy filtering introduced by SnOx-NPs cause dramatic Seebeck coefficient enhancement. The obtained optimized power factor (116 μWm-1K-2) is among the highest reported for any organic-inorganic hybrid system. This easy and efficient strategy promises well for future mass production of flexible thermoelectric devices and the mechanism revealed here may inspire future research on thermoelectrics and flexible electronics.

12:05 - 12:15
2.1-T3
Cortés-Villena, Alejandro
Universidad de Valencia - ICMol (Institute of Molecular Science)
Sensitized Emission of Perovskites by Lanthanide-Doped Upconversion Nanoparticles and Their Self-Assembly
Cortés-Villena, Alejandro
Universidad de Valencia - ICMol (Institute of Molecular Science), ES

I am currently a Ph.D. student at the University of Valencia (Spain). I belong to the Photochemistry Reactivity Group of Julia Pérez Prieto. My occupation is focused on the synthesis and characterization of photoactive semiconductor nanoparticles, specifically, on perovskite nanoparticles.

 

Authors
Alejandro Cortés-Villena a, Nestor Estebanez a, Juan Ferrera-González a, María González-Béjar a, Raquel E. Galian a, Soranyel González-Carrero a, Julia Pérez-Prieto a
Affiliations
a, Universidad de Valencia - ICMol (Institute of Molecular Science), Catedrático José Beltrán Martinez 2, Paterna, ES
Abstract

The preparation of 1D superlattices from colloidal building blocks is intriguing but challenging due to the anisotropy attributes and lack of directional interactions between isotropic nanoparticles (NPs) [1]. The preparation of ordered superlattices of assembled NPs is a research topic of great interest to gain insight into their collective properties. [2]

We present here the first preparation of linear coassembly of lead halide perovskites and lanthanide-doped upconversion nanoparticles both as colloid and solid film deposited on a glass substrate [3]. Efficient sensitized upconversion of cesium lead halide perovskite nanoparticles (CsPbX3 NPs; X = Cl-, Br-, I-) can be accomplished by nearby lanthanide-doped upconversion nanoparticles (NaYF4:Yb3+, Ln3+ NPs; Ln3+ = Tm3+, Er3+) under near-infrared (NIR) excitation thanks to linear coassembly of both colloidally-dispersed nanoparticles mediated by lead sulfate molecular clusters. The photophysical properties of the coassembly, specifically, the lifetime of the sensitized perovskite emission and the efficiency of the non-radiative lanthanide resonance energy transfer (LRET) process showed a strong dependence on the irradiance and the sample state. Besides, it is worth mentioning the enhanced stability of the perovskite NP inside the nanohybrid under atmospheric conditions as well as in direct contact with water. We believe this system would be a good candidate for light-harvesting applications in the near future.

12:15 - 12:45
Discussion
PERIMPED 2.2
Chair: Pablo P. Boix
11:45 - 11:55
2.2-T1
Riquelme, Antonio J
Applying Small Perturbation Techniques on Perovskite Solar Cells. Combining Experiments with Drift Diffusion Modelling
Riquelme, Antonio J
Authors
Antonio J Riquelme a, Lawrence Bennett b, Francisco Gálvez a, Nicola Courtier b, Lidia Contreras-Bernal a, d, Matthew Wolf c, Hernán Míguez d, Alison Walker c, Giles Richardson b, Juan Anta a
Affiliations
a, Pablo de Olavide University, Sevilla, Spain, Carretera de Utrera, km. 1, Montequinto, ES
b, Department of Mathematical Sciences, University of Southampton, University of Southampton, Southampton, SO17 1BJ, GB
c, University of Bath, Department of Physics, Claverton Down, Bath BA2 7AY, GB
d, Instituto de Ciencia de Materiales de Sevilla (CSIC-US), ES, Calle Américo Vespucio, 49, Sevilla, ES
Abstract

Metal Halide Perovskites (MHPs) are mixed electronic–ionic semiconductors with an extraordinary complex optoelectronic behaviour and a record efficiency surpassing 25%. Interpreting small perturbation response of perovskite solar cells (PSCs) is significantly more challenging than for most other photovoltaics. This is for a variety of reasons, of which the most significant are the mixed ionic-electronic conduction properties of metal halide perovskites and the difficulty in fabricating stable, and reproducible, devices. Experimental studies, conducted on a variety of PSCs, produce a variety of spectra shapes, with different physical interpretations.
The impedance response has commonly been analyzed in terms of sophisticated equivalent circuits that can be hard to relate to the underlying physics and which complicates the extraction of efficiency-determining parameters. By a combination of experiment and drift-diffusion (DD) modelling of the ion and charge carrier transport and recombination within the cell, the main features of common impedance spectra are well reproduced by the DD simulation. Based on this comparison, we show that the high frequency response contains all the key information relating to the steady-state performance of a PSC, focusing on the charge collection efficiency of the device. We also analyze Intensity Modulated Photocurrent Spectroscopy ( IMPS) data in MHPs based on the analysis of the internal quantum efficiency, connecting them to the charge collection obtained from Impedance, and the time signals featuring in the frequency spectra. We look at the change of each signal when optical excitation wavelength, photon flux, and temperature are varied for an archetypical methyl ammonium lead iodide solar cell. We compare the Perovskite IMPS results with relatively simpler dye-sensitized solar cells (DSC) with viscous and non-viscous electrolytes to help us to understand the origin of the three signals appearing in MHP cells and the measurement of the internal quantum efficiency.

11:55 - 12:05
2.2-T2
Zeiske, Stefan
Department of Physics, Swansea University, UK
Ultra-sensitive external quantum efficiency measurements of organic solar cells
Zeiske, Stefan
Department of Physics, Swansea University, UK, GB
Authors
Stefan Zeiske a, Christina Kaiser a, Nasim Zarrabi a, Oskar J. Sandberg a, Wei Li a, Drew B. Riley a, Paul Meredith a, Ardalan Armin a
Affiliations
a, Sustainable Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, UK, Singleton Park, Swansea, SA2 8PP Wales, GB
Abstract

The measurement of the photovoltaic external quantum efficiency (EQE) at photon energies well below the bandgap of semiconductors is becoming increasingly important for achieving a better understanding of the contribution of intra- and intermolecular states involved in the charge generation and recombination process in solar cells and photodetectors. In this work, we present an optical and electrical noise-minimized EQE apparatus exceeding 100 dB dynamic range by carefully identifying and studying several apparatus- and device-related factors limiting the sensitivity of EQE measurements, such as stray light level of the output monochromator, flicker and pick-up noise, photon noise of the light bias source and electrical and thermal shot noise of the device.1 By minimizing these factors, we are able to detect EQE signals as small as -100 dB derived from weak sub-gap absorption features in organic, inorganic and perovskite semiconductors.2 These ultra-sensitive EQE measurements allow us to directly observe sub-gap trap states in a large variety of organic solar cells significantly lower in energy than the corresponding charge-transfer states.3

12:05 - 12:15
2.2-T3
Bou, Agustín
Spectral Correlation of Electrooptical Frequency Techniques in Perovskite Solar Cells Beyond Impedance Spectroscopy
Bou, Agustín
Authors
Agustín Bou a, Adam Pockett b, Dimitrios Raptis b, Trystan Watson b, Matthew J. Carnie b, Juan Bisquert a
Affiliations
a, Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, ES
b, SPECIFIC – Swansea University, Materials Research Centre, College of Engineering, UK, Bay Campus, Swansea, SA1 8EN,, SWANSEA, GB
Abstract

Small perturbation techniques have been widely used for the investigation of perovskite solar cells and have helped understand important aspects of their operation. An adequate interpretation of the spectra given by impedance spectroscopy (IS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) is key for the understanding of device operation. The utilization of a correct equivalent circuit to fit the spectra and extract real parameters is needed to get this information and provide a proper interpretation. In this work, we present an equivalent circuit based on previous studies, which is able both to reproduce the most general features and also the exotic behaviours found in impedance spectra. From the measurements, we demonstrate that the mid-frequency features that appear in IS spectra clearly depend on the active layer thickness and we prove the spectral correlation of the three techniques that has been suggested theoretically.

12:15 - 12:25
2.2-T4
Riley, Drew B.
Sustainable Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, UK
Direct quantification of quasi-Fermi level splitting in organic thin film devices
Riley, Drew B.
Sustainable Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, UK, GB

Drew attended Dalhousie University in Halifax Canada, where he completed his B.Sc. with honours and his M.Sc in Physics. During his undergraduate degree, he was awarded the A.S. Mackenzie prize for first class honours and a CGSM scholarship to attend his master’s studies. During his master’s work he studied femto-second spin-relaxation within perovskite semiconductors and gained expertise in femto-second laser systems, inorganic deposition techniques, and vacuum systems. Following his master's degree Drew was awarded a PGS-Doctorial scholarship.

In 2019, Drew moved to Swansea to begin his PhD studies with the Sêr SAM group at Swansea University. His focus is on the disentangling of various relaxation pathways in disordered semiconductor systems including organics and perovskites. He is the resident Ultrafast expert and has been involved in the construction of many apparatuses the group currently uses. Drew’s interests lie in ultrafast and semiconductor physics, specifically the relaxation mechanisms in disordered semiconductors.

Throughout his career, Drew has worked with start-up companies, lectured to undergraduate students, tutored and taught at the undergraduate level, and volunteered with various science outreach groups. Before studying at Dalhousie, Drew worked as a pastry chef, he is an avid musician, surfer, and traveller.

Authors
Drew B. Riley a, Oskar J. Sandberg a, Nora M. Wilson b, Wei Li a, Stefan Zeiske a, Nasim Zarrabi a, Paul Meredith a, Ronald Osterbacka b, Ardalan Armin a
Affiliations
a, Sustainable Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, UK, Singleton Park, Swansea, SA2 8PP Wales, GB
b, Physics, Faculty of Science and Engineering, Åbo Akademi University, Turku Finland, FI
Abstract

Non-radiative losses to the open-circuit voltage are a primary factor in limiting the power conversion efficiency of organic photovoltaic solar cells. The dominate non-radiative loss is intrinsic to the active layer which, along with the thermodynamic limit to the open-circuit voltage, define the quasi-Fermi level splitting (QFLS). Acurate quantification of the QFLS would allow for a complete description of the non-radiative losses occuring with a device. However, quantification of the QFLS in organic thin film devices with low mobility is challenging due to the excitonic nature of photoexcitation in the active layer and additional sources of non-radiative loss associated with the device structure. In this presentation I will outline an experimental approach based on electro-modulated photoluminescence to quantify the QFLS in organic solar cells. Drift-diffusion simulations are used to show that this method accurately predicts the QFLS in the bulk of the device regardless of device-related non-radiative losses. State-of-the art organic solar cells with varying electrode-induced non-radiative losses are created using PM6:Y6 as an active layer. The QFLS is quantified for each device and is shown to be independent of device architecture. This work provides a method to quantify the QFLS of organic solar cells under operational conditions, fully characterizing the magnitude of different contributions to the non-radiative losses of the open-circuit voltage. This method will be a useful tool for researchers optimizing organic solar cells, light-emitting diodes, or photodetectors.

12:25 - 12:55
Discussion
12:00 - 12:05
DSSC Opening nanoGe
12:05 - 12:15
DSSC Session Introduction 2.1
NanoLigh 2.2
Chair: Alexander Urban
12:05 - 12:15
2.2-T1
Goñi, Alejandro R.
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
Photoluminescence of Bound-Exciton Complexes and Assignment to Shallow Defects in Methylammonium/ Formamidinium Lead Iodide Mixed Crystals
Goñi, Alejandro R.
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain, ES
Authors
Adrián Francisco-López a, Bethan Charles b, Ma. Isabel Alonso a, Miquel Garriga a, Mark T. Weller c, d, Alejandro R. Goñi a, e
Affiliations
a, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain, Campus UAB, Bellaterra, ES
b, Dept. of Materials Science and Metallurgy University of Cambridge, Cambridge CB3 0FS, UK
c, Dept. of Chemistry & Centre for Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath BA2 7AY, UK
d, Dept. of Chemistry, Cardiff University, Wales CF10 3AT, UK
e, ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain
Abstract

The high defect tolerance of metal halide perovskites, in terms of their exceptional optoelectronic properties, is assumed to be due to the very fact that most native point defects are shallow, which does not contribute to the non-radiative recombination of free carriers. Here, a systematic study is presented [1,2], which concerns the evolution of shallow-defect signatures observed at low temperatures in the photoluminescence (PL) spectra of mixed organic cation lead iodide perovskite single crystals (FAxMA1−xPbI3, where MA stands for methylammonium and FA for formamidinium). Below ≈ 100 K, a number of peak-like features become clearly apparent in the PL spectra at energies lower than the strong free-exciton emission, which are related to the radiative recombination of bound exciton complexes associated with native shallow defects (donors and/or acceptors). Based on state-of-the-art ab initio calculations [3], a tentative assignment is provided for all PL features to different shallow-defects (Pb, I, and MA vacancies as well as I interstitials) typically present in hybrid perovskites. The defect-related signatures exhibit a clear trend regarding the mixed-crystal composition, indicating that the material becomes less prone to defect formation with increasing FA content.

12:15 - 12:25
2.2-T2
Hopper, Tom
Department of Chemistry and Centre for Plastic Electronics, Imperial College London
Hot carrier trapping in InP/ZnSe quantum dots
Hopper, Tom
Department of Chemistry and Centre for Plastic Electronics, Imperial College London, GB

Tom Hopper obtained his MChem from Newcastle University and Ph.D. from Imperial College London, both in Chemistry. He seeks to fast track the development of new optoelectronic materials and devices by elucidating their properties at the most fundamental level. During his doctoral research in the group of Dr. Artem Bakulin, Tom played a pioneering role in the design and construction of femtosecond optical control experiments, and applied them to pinpoint efficiency-limiting processes in emerging photovoltaic systems based on organic and hybrid materials. Also during this time, and subsequently as an EPSRC Doctoral Prize Fellow at Imperial, Tom led his own research thrust on the photophysics of quantum-confined semiconductors and their mesoscale assemblies.

Authors
Tom Hopper a, Artem Bakulin a
Affiliations
a, Department of Chemistry and Centre for Processible Electronics, Imperial College London
Abstract

InP-based quantum dots are at the forefront of commercial light-emitting applications due to their bright emission, size-tunable optical behaviour and non-toxic material composition. Furthermore, the emission spectra of these materials is dominated by the lowest-energy bandedge electronic states.  Here we record the transient photoluminescence from non-resonantly excited colloidal InP/ZnSe core-shell QDs to reveal highly non-exponential behaviour in the microsecond time regime, pointing toward a hot carrier trapping and detrapping process long before light emission occurs. To further elucidate the dynamics and extent of the hot carrier trapping in the QDs, we implement ultrafast “pump-push-probe” spectroscopy. The results show that ~40% of hot carriers with an excess energy of ~ 1eV are trapped before cooling can take place on the ~600 fs timescale. These trapped carriers return to the bandedge and radiatively recombine on the microsecond timescale.

12:25 - 12:35
2.2-T3
Muscarella, Loreta
AMOLF Institute
Pressure-induced compression to manipulate phase-segregation in mixed-halide perovskites
Muscarella, Loreta
AMOLF Institute, NL
Authors
Loreta Muscarella a, Eline Hutter a, b, Francesca Wittmann a, Young Won Woo c, Young-Kwang Jung c, Lucie McGovern a, Jan Versluis a, Huib Bakker a, Aron Walsh c, d, Bruno Ehrler a
Affiliations
a, AMOLF Institute, Science Park, Amsterdam, NL
b, Utrecht University, The Netherlands, Princetonplein, 1, Utrecht, NL
c, Department of Materials Science and Engineering, Yonsei University, 03722 Seoul, Korea
d, Department of Materials, Imperial College London
Abstract

Halide perovskite semiconductors have recently gathered significant attention due to their intriguing optoelectronic properties combined with low-cost and simple fabrication method. In addition, the easy bandgap tunability of this material by changing the ratio of halides in the chemical composition, makes them promising candidate for LEDs and tandem solar cells in combination with silicon. However, illuminating mixed-halide perovskites results in the formation of segregated phases enriched in a single halide. Phase segregation affects the homogeneity of the bandgap compromising the purity and the quality of the absorption/emission and therefore its applications. This segregation occurs through ion migration, which is also observed in pure-halide compositions, and whose control is essential to enhance lifetime and stability.

In this work, we investigate how pressure-induced compression affects the kinetics [1] and thermodynamics [2] aspects of phase segregation in mixed halide perovskite MAPbBrxI1-x (xbr-= 0.25, 0.5 and 0.7). Using pressure-dependent transient absorption spectroscopy, we find that the formation rates of both iodide- and bromide-rich phases in MAPb(BrxI1-x)3 reduce by ~2 orders of magnitude upon increasing pressure to 0.3 GPa. We interpret this change as a compression-induced difference in the activation energy for ion migration, which is supported by first-principle calculations. A similar mechanism occurs when the unit cell volume is reduced by incorporating a smaller cation. Furthemore, we find that high external pressure increases the range of stable halide mixing ratios by alteration of the Gibbs free energy via the largely overlooked PΔV term.

These findings reveal that stability with respect to halide segregation can be achieved either physically through compressive stress or chemically through compositional engineering and that in principle any iodide-bromide ratio can be thermodynamically stabilized by tuning the unit cell volume.

12:35 - 12:45
2.2-T4
Nandayapa, Edgar
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany
Unraveling Dynamic and Static Quenching Processes of Oxygen, Nitrogen, Argon and Water in Metal Halide Perovskites at Moderate Photon Flux Densities
Nandayapa, Edgar
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, DE
Authors
Edgar Nandayapa a, Katrin Hirselandt a, Christine Boeffel b, Eva Unger a, Emil List-Kratochvil c
Affiliations
a, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, Berlin, DE
b, Fraunhofer Institute for Applied Polymer Research
c, Humboldt-Universität zu Berlin, Brook-Taylor-Straße, 6, Berlin, DE
Abstract

Metal halide perovskites undergo changes when illuminated under ambient conditions. Excited perovskite layers in the presence of argon, nitrogen, oxygen, and water show dynamic and static photoluminescence quenching effects, as well as passivation, under low illumination densities equivalent to 1 sun. In our experiment, we exposed perovskite layers to discrete partial pressures of the mentioned gasses. By applying the Stern-Volmer model to the results, we found that all gases showed a primarily static quenching effect, that is, they were adsorbed to the crystallites. At the same time, weak dynamic quenching effects were present. These effects are detectable at partial pressures as low as 1 mbar and are mostly reversible once the quenching molecules are removed. Our observations demonstrate an interplay between the excitation photon flux density and the resulting quenching or passivation effect. In particular, oxygen and nitrogen lead to a significant but reversible static quenching, while an H2O atmosphere showed a slightly more dynamic-type quenching process. In the case of argon, it first showed a minor PL increase at low pressures, a sign of passivation. Yet, at higher pressures, argon showed a moderate quenching effect that had not been previously documented. These results emphasize the importance of proper sample atmospheric conditioning during preparation and characterization of the samples.

12:45 - 13:15
Discussion
DSSC 2.1
Chair: Marina Freitag
12:15 - 12:35
2.1-I1
Di Carlo, Aldo
CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’
Toward Stable Dye Sensitized Solar Modules
Di Carlo, Aldo
CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, IT
Aldo Di Carlo is Full Professor of Optoelectronics and Nanoelectronics at the Department of Electronics Engineering of the University of ROme "Tor Vergata". His research focuses on the study and fabrication of electronic and optoelectronic devices, their analysis and their optimization. Di Carlo is Director of the Center for Hybrid and Organic Solar Cells (CHOSE) which involve more than 30 researchers dealing with the development of organic solar cells (DSC, OPV and Perovskite) and on scaling-up of these technologies for industrial applications. CHOSE has generated 5 spin-off company and a public/private partnership. Di Carlo is author/coauthor of more than 300 scientific publications in international journals, 13 patents and has been involved in several EU projects (two as EU coordinator)
Authors
Aldo Di Carlo a, Paolo Mariani a, Luigi Vesce a, Andrea Reale a
Affiliations
a, CHOSE (Centre for Hybrid and Organic Solar Energy), University of Rome ‘‘Tor Vergata’’, via del Politecnico 1, Rome 00133, Italy
Abstract

Owing to its peculiar properties such as transparency, weak angle dependence and a better response in case of diffused light with respect to technology based solely on semiconductors, DSSCs (Dye Sensitized Solar Cells) are well suited for Building Integrated PhotoVoltaics (BIPV) and energy harvesting for indoor applications. In this presentation, we will describe the effort made to stabilize Dye Sensitized Solar Modules (DSSMs) of different sizes up to 20x30 cm2. We implemented several strategies to face external and internal issues and to pass both light soaking (1000 h @ 1Sun) and damp heat (1000 h @ 85°C-85% RH) stability tests. In particular, at the cell level, we optimize the electrolyte composition also with respect to the dye used as sensitizer. On the other hand, we introduced Z-Type DSSMs with screen printed graphene-based vertical interconnections.[1] This prevents corrosion of interconnections in contact with the electrolytic species (typically iodide/triiodide), unlike conventional architectures, and increases the geometrical fill factor. Several applications of stabilized modules will be shown such as vision and spandrel glass for building façade, indoor and for Greenhouses.

 

12:35 - 12:55
2.1-I2
Barolo, Claudia
University of Turin
NIR functional dyes for transparent and colorless Dye-sensitized Solar Cells
Barolo, Claudia
University of Turin
Authors
Nadia Barbero a, Raffaele Borrelli b, Fionnuala Grifoni c, Amalia Velardo b, Waad Naim c, Marco Giordano a, Yameng Ren d, Shaik M. Zakeeruddin d, Fabio Matteocci e, Thomas Alnasser c, Matteo Bonomo a, Ilias Nikolinanos f, Stefan Haacke f, Aldo Di Carlo e, Michael Graetzel d, Claudia Barolo b, Frederic Sauvage b
Affiliations
a, Department of Chemistry, NIS Interdepartmental and INSTM Reference Centre, University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy
b, Dipartimento di Scienze Agrarie, Forestali e Alimentari, University of Torino, Largo Paolo Braccini 2, Grugliasco 10095, Italy
c, Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne (UPJV), CNRS UMR 7314, 33 rue Saint Leu, 80039 Amiens, France.
d, Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Photonics and Interfaces, Station 6, 1015 Lausanne, Switzerland
e, CHOSE (Centre for Hybrid and Organic Solar Energy), University of Rome ‘‘Tor Vergata’’, via del Politecnico 1, Rome 00133, Italy
f, IPCMS, UMR 7504, 23, rue du Loess, 67034 Strasbourg, France
Abstract

NIR-sensitizers in Dye-sensitized Solar Cells are usually conceived in order to build co-sensitized solar cells or tandem devices, taking in account that NIR conversion can widen solar harvesting and tune the colors of final devices. However, due to the fact that at least 25 % of the solar light available on earth surface is composed by Far-red/NIR frequencies, it would be also interesting to exploit only the NIR part of the spectrum in order to create a solar window with high transparency and still an interesting efficiency. [1,2]

In this contribution we will present the design strategies (with a computational insight), the main synthetic routes and the full characterization of a series of polymethine-based dyes to be applied on transparent dye-sensitized solar cells. We consider the Human eye photopic response to optimize a selective near-infrared sensitizer by conferring to the dye the ability to strongly and sharply absorptive beyond 800nm (S0-S1 transition) while rejecting the upper S0-Sn contributions far in the blue where the human retina is poorly sensitive.

We will discuss the main problems related to this specific approach able to keep the visible transmittance higher than 75% looking forward to a non-intrusive solar cell technology.

12:55 - 13:15
Discussion
12:45 - 14:00
CHEMNC Break
12:45 - 14:00
SOLFUL Break
12:55 - 14:00
PERIMPED Break
13:15 - 14:00
DSSC Break
13:15 - 15:30
NanoLight Break
14:00 - 14:10
CHEMNC Session Introduction 2.2
DSSC 2.2
Chair: Neil Robertson
14:00 - 14:10
2.2-T1
Giordano, Marco
Dept. Chemistry - University of Turin - (Italy)
Synthesis of Quaterrylene-Based Dyes for NIR Dye-Sensitized Solar Cells
Giordano, Marco
Dept. Chemistry - University of Turin - (Italy), IT
Authors
Marco Giordano a, Andrea Fin b, Matteo Bonomo a, Nadia Barbero a, Claudia Barolo a, Guido Viscardi a
Affiliations
a, Dipartimento di Chimica, NIS Interdepartmental and INSTM Reference Centre, Università di Torino, Torino, Italy
b, Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Torino, Italy
Abstract

Photovoltaic cells based on semiconductor technology are, nowadays, the most efficient and easily available systems for solar energy conversion. Dye-Sensitized Solar Cells (DSSCs) are very promising owing to low production costs, transparency and ability to harvest diffused light.1 Building Integrated PhotoVoltaics (BIPV) based on DSSC are an emerging application to make DSSC more attractive in the energy production field. An innovative and powerful approach resides on the implementation of colourless DSSCs based on NIR sensitizers such as polymethine and rylene dyes.2,3 Whereas well-known NIR sensitizers like phthalocyanines and polymethine dyes are still characterized by a significant absorption in the visible window, extended rylene dyes such as quaterrylene could be allow the assemble of a totally colourless DSSCs.2,3 In this work, we present the synthesis of two quaterrylene dyes to evaluate their application as NIR-sensitizers in DSSCs. Different synthetic pathways were explored to functionalize the rylene core to modulate the photophysical and electronic requirements and to improve the processability properties of the final materials. The photophysical and electrochemical properties were investigated. The assemble and study of devices based on quaterrylene dyes is under investigation and the preliminary results will be presented.

14:10 - 14:20
2.2-T2
Pinto, Ana Lucia
NOVA School of Science and Technology
Optimizing the Structure of Dye-Sensitized Solar Cell Sensitizers from Red Wine
Pinto, Ana Lucia
NOVA School of Science and Technology, PT
Authors
Ana Lucia Pinto a, Hugo Cruz a, Joana Oliveira b, Paula Araújo b, Luis Cruz b, Vânia Gomes b, Cassio P. Silva c, Gustavo T. M. Silva c, Giuseppe Calogero d, Victor de Freitas b, Frank H. Quina c, Fernando Pina a, A. Jorge Parola a, J. Carlos Lima a
Affiliations
a, LAQV-REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
b, LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal
c, Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Cidade Universitária, São Paulo 05508-000, Brazil
d, CNR, Instituto per i Processi Chimico-Fisici, Sede di Messina, Salita Sperone, C. da Papardo, I-98158 Faro Superiore Messina, Italy
Abstract

Dye-Sensitized Solar Cells (DSSCs) are photovoltaic devices based on the sensitization of wide band-gap semiconductor electrodes with dyes absorbing visible light. The first reported DSSC using a natural anthocyanin displayed a conversion yield of 0.56 %, paving the way for sustainable DSSCs.[1] Also anthocyanin derivatives present in aged red wines such as pyranoanthocyanins display great potential as photosensitizers for bio-inspired DSSCs. In this work, several bio-inspired pyranoanthocyanin derivatives were designed, synthesized and applied as dye sensitizers in DSSCs. The current vs. potential properties of photoanodes using these dyes pointed to the relationship between power conversion efficiency and dye structure. These included the influence of the donor group, π-conjugation and the type of anchoring unit on the adsorption of the dyes to TiO2 and on the overall performance of the DSSCs. Specifically, the presence of a catechol unit was shown to increase electron injection into the TiO2 semiconductor. Moreover, ‘dual-mode anchoring’ (OH vs. amino) to TiO2 was achieved through acidification of the medium. Overall non-optimized efficiencies up to 2.6 % were achieved, which substantiates the importance of this family as potential dye-sensitizers for practical DSSC applications.

14:20 - 14:30
2.2-T3
Michaels, Hannes
Uppsala University, Sweden
Dye-sensitized Solar Cells under Ambient Light: Powering Autonomous Smart Sensors for the Internet of Things
Michaels, Hannes
Uppsala University, Sweden, SE
Authors
Hannes Michaels a, Michael Rinderle b, Alessio Gagliardi b, Marina Freitag c
Affiliations
a, Department of Chemistry − Ångström Laboratory, Physical Chemistry, Uppsala University, Sweden, SE
b, Technical University of Munich, Department of Electrical and Computer Engineering, DE
c, School of Natural and Environmental Sciences, Newcastle University, UK, Newcastle upon Tyne, Reino Unido, Newcastle upon Tyne, GB
Abstract

The field of photovoltaics holds the opportunity to make our buildings smart and our portable devices independent, provided effective energy sources can be developed for use in ambient indoor conditions. To address this important issue, ambient light dye-sensitized photovoltaic cells were developed to power autonomous Internet of Things (IoT) devices, capable of machine learning, allowing the on-device implementation of artificial intelligence. Through aco-sensitization strategy, we tailored dyesensitized photovoltaic cells based on a copper(II/I) electrolyte for the generation of power under ambient lighting with a conversion efficiency of 34%, 103 mW cm2 at 1000 lux; 32.7%, 50 mW cm2 at 500 lux and 31.4%, 19 mW cm2 at 200 lux (fluorescent lamp). A small array of DSCs with a joint active area of 16 cm2 was then used to power machine learning on wireless nodes. The collection of 0.947 mJ or 2.72  1015 photons is needed to compute one inference of a pre-trained artificial neural network for MNIST image classification in the employed set up. The inference accuracy of the network exceeded 90% for standard test images and 80% using camera-acquired printed MNISTdigits.

14:30 - 14:40
Abstract not programmed
14:40 - 15:10
Discussion
14:00 - 14:10
PERIMPED Session Introduction 2.3
14:00 - 14:10
SOLFUL Session Introduction 2.2
CHEMNC 2.2
Chair: Maksym Yarema
14:10 - 14:30
2.2-I1
Cabot, Andreu
Catalonia Institute for Energy Research (IREC)
Transition metal chalcogenide and phosphide nanocrystals for lithium−sulfur batteries
Cabot, Andreu
Catalonia Institute for Energy Research (IREC), ES
Authors
Andreu Cabot a, b
Affiliations
a, Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1, Sant Adria del Besos, ES
b, ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain
Abstract

Lithium-sulfur batteries (LSBs) are one of the most promising candidates to replace lithium-ion batteries (LIBs) in next-generation energy storage systems. Compared with LIBs, LSBs are characterized by a sixfold higher theoretical energy density, 2600 W h kg−1, and a potentially lower cost and environmental impact if properly selecting the cathode materials. Despite these attractive advantages, the electrically insulating character of sulfur and the shuttle effect of intermediate lithium polysulfides (LiPS) greatly limits the practical application of LSBs. Additionally, the serious volume changes and slow redox kinetics during the charging/discharging process also reduce the cycling life and power density.

Several sulfur host materials have been proposed to overcome the aforementioned limitations. Carbon-based hosts with high electrical conductivity and large specific surface area have been employed to disperse sulfur species and confine the volume expansion. However, the weak physical interaction between LiPS and the non-polar surfaces of these materials makes them ineffective to capture soluble LiPS, which results in a serious shuttle effect and a reduced cyclability. Alternatively, transition metal chalcogenides and phosphides may simultaneously provide the required large electrical conductivity, polar surfaces and high catalytic activity towards Li-S redox reactions. To maximize the amount of LiPS adsorption sites and catalytic activity, these transition metal-based materials should be nanostructured. In this direction, nanocrystals can provide high surface areas and abundant unsaturated sites and defects to effectively reduce the reaction energy barrier.

In this talk, I will discuss our recent results in this direction, providing several examples of the materials we have developed to be used as the sulfur host in the cathode of LSBs.

14:30 - 14:50
2.2-I2
McDowell, Matthew
Georgia Institute of Technology
In Situ Investigation of Transformations in Nanocrystals for Batteries
McDowell, Matthew
Georgia Institute of Technology, US
Authors
Matthew McDowell a
Affiliations
a, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, 30332, US
Abstract

Battery electrodes made from nanomaterials can be useful for increasing charge storage capacity and extending cycle life, but it is critical to understand and control reaction mechanisms in such materials for optimal performance [1]. Here, I discuss my group’s efforts in using in situ transmission electron microscopy (TEM) characterization to investigate reaction mechanisms in nanocrystals for batteries. First, I will present our investigation of reversible void nucleation and growth during lithiation and delithiation of antimony (Sb) alloy nanocrystals [2]. Sufficiently small Sb alloy nanocrystals were found to form single voids during dealloying with lithium rather than undergoing shrinkage, as in larger particles. This effect is due to a mechanically stiff outer oxide shell that retains its shape, as indicated by a chemo-mechanical model of the transformation process. Importantly, the voiding behavior translated to improved electrochemical behavior in battery cells due to the lack of surface dimensional changes of the materials. Next, a study on chemo-mechanical degradation of FeS2 nanocrystals reacting with different ions (lithium, sodium, and potassium) is presented [3]. Despite larger volume changes during reaction with Na+ and K+, only reaction with Li+ was observed to cause fracture of these nanocrystals. Modeling showed that this surprising result was found to be due to the shape of the reaction front as it evolves during reaction, with sharp corners during lithiation resulting in stress concentration and fracture. Finally, I will briefly discuss in situ investigations of the effect of intercalated species on thermal stability of nanoscale materials [4]. Together, these studies highlight the importance of detailed understanding of reaction mechanisms at the nanoscale, which can be used to guide the development of batteries with improved performance.

14:50 - 15:10
2.2-I3
Sargent, Edward
University of Toronto
The chemistry of colloidal quantum dots for application in light-emitting devices
Sargent, Edward
University of Toronto, CA

Ted Sargent received the B.Sc.Eng. (Engineering Physics) from Queen's University in 1995 and the Ph.D. in Electrical and Computer Engineering (Photonics) from the University of Toronto in 1998. He holds the rank of Professor in the Edward S. Rogers Sr. Department of Electrical and Computer Engineering at the University of Toronto, where he holds the Canada Research Chair in Nanotechnology and serves as a KAUST Investigator. His book The Dance of Molecules: How Nanotechnology is Changing Our Lives (Penguin) was published in Canada and the United States in 2005 and has been translated into French, Spanish, Italian, Korean, and Arabic. He is founder and CTO of InVisage Technologies, Inc. He is a Fellow of the AAAS “...for distinguished contributions to the development of solar cells and light sensors based on solution-processed semiconductors.” He is a Fellow of the IEEE “... for contributions to colloidal quantum dot optoelectronic devices.”

Authors
Edward Sargent a
Affiliations
a, Department of Electrical and Computer Engineering, University of Toronto, Canada, King's College Road, 10, Toronto, CA
Abstract

I will discuss the engineering of the surface chemistry of colloidal quantum dots with applications in LEDs the goal. I will include a discussion of the surface chemistry that is specific to perovskites, where the goal is simultaneously to passivate and also avoid the redispersion of the constituent perovskites into the solution, a challenge given the polar solvents often employed and the partially ionic nature of the perovskites. I will link this chemistry and physics to the key requirements of LED active layers, including efficient radiative recombination, and also efficient and balanced electron injection and hole injection from transport layers into the active layer. 

15:10 - 15:30
Discussion
PERIMPED 2.3
Chair: Elizabeth von Hauff
14:10 - 14:30
Abstract not programmed
14:30 - 14:50
2.3-I1
Romero, Beatriz
Universidad Rey Juan Carlos (URJC)
Dynamical mechanisms in CsFaPbIBr perovskite solar cells characterized by impedance spectroscopy and time resolved techniques
Romero, Beatriz
Universidad Rey Juan Carlos (URJC), ES
Authors
Beatriz Romero a, Belén Arredondo a, Gonzalo del Pozo a, Enrique Hernández a, Diego Martín a, Yulia Galagan c, José Carlos Pérez a, Laura Muñoz a, María del López a, Mehrdad Najafi b
Affiliations
a, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos
b, TNO, partner of Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands
c, National Taiwan University, Department of Materials Science and Engineering, Taipei, TW
Abstract

Currently, Perovskite Solar Cells (PSCs) is one of the most promising third generation photovoltaic technologies, due to the outstanding properties of this hybrid material, such as high absorption coefficient, high defect tolerance, and long diffusion lengths, together with the low-cost and ease of scalability. In only a few years, the efficiency has risen from 3.4 % up to 25.5 %. With the aim of increasing the efficiency without compromising the device stability, the development of new materials, such as mixed cation mixed halide perovskite, has attracted the attention of many research groups.

In this context, CsFaPbIBr PSCs with different active layer thicknesses, ranging from 350 nm to 650 nm) have been fabricated and characterized. The initial efficiency is around 13-14% for all thicknesses. Cells have been degraded using ISOS-L1 degradation protocol, i.e., cells have been light soaked under constant 1 sun illumination. Results show that all the samples exhibit a dramatic burn-in degradation at the initial stage, resulting in a drop of the efficiency down to 80 %, 60 % and 45 % for devices of 650 nm, 500 nm and 350 nm respectively during the first 10 minutes of operation. Besides, after 15-20 minutes of light irradiation, thin and medium samples stabilized, while thicker ones continue decaying. Impedance Spectroscopy (IS) has been measured every 15 minutes. Experimental IS data have been fitted using the Matryoshka circuit with 3 RC/RCPE sub-circuits, and circuital parameters have been extracted. From the temporal evolution of these parameters, we conclude that non-stabilization of the efficiency for the thicker samples can be related with the increase of the medium-low frequency capacitance in these devices, associated to charge accumulation at the interface.  

Additionally, we have experimentally explored the relationship between the low-frequency impedance feature of CsFAPbIBr photovoltaic perovskites, based on non-ideal capacitive effects (constant phase element, CPE), and the long-tailed memory photocurrent during stepwise-JV analysis. Our model, based on fractional calculus theory, produced optimal fits for the transient data, allowing a physical interpretation consistent with the mechanisms occurring in perovskite layers of different thicknesses. It is reported that hysteresis increases with more prominent anomalous capacitive phenomena, suggesting that trapping events limit ion motion and carrier transport.

14:50 - 15:10
Discussion
SOLFUL 2.2
Chair not set
14:10 - 14:30
2.2-I1
Cheng, Jun
Xiamen University
Chemical dynamics in catalysis and electrochemistry
Cheng, Jun
Xiamen University, CN

Jun Cheng received his PhD in Chemistry at the Queen’s University Belfast, UK in 2008, and the subject was simulating surface catalysis using density functional theory. He then moved to the University of Cambridge, first as a postdoc for two years developing ab initio molecular dynamics based method for calculation of redox potentials and acidity constants. In 2010-2013, he was awarded a junior research fellowship by Emmanuel College at Cambridge, which granted him freedom to pursue his interest in interfacial electrochemistry. He became a university lecturer at the University of Aberdeen, UK in 2013, and was soon rewarded the major national start-up program fund and took up a full professorship in Xiamen University, China. Over years, his research has shifted from computational surface science and heterogeneous catalysis, to method development in redox and acid-base chemistry, and to ab inito electrochemistry. His recent research interest is combining electronic structure, sampling and machine learning methods for studying chemical dynamics in catalysis and electrochemistry.

Authors
Jun Cheng a
Affiliations
a, Xiamen University, School of Electronic Science and Engineering Xiamen University Xiamen, China, Xiamen, CN
Abstract

It is known that energy materials undergo dynamic structural changes at in-situ/in-operando conditions. Yet, the majority of computational studies only consider the static structures of energy materials. When the materials are submerged in liquid solution, dynamic solvation effects are usually ignored, or treated with dielectric continuum models, often lacking validation. The situations are about to change. Thanks to the latest development of in-situ experimental techniques and state-of-the-art computational methods, materials dynamics has recently drawn more and more attentions in many research areas. In this talk, I will present our recent progress on modeling dynamic catalysis and electrochemistry using Ab Initio Molecular Dynamics (AIMD) [1-4]. When statistical sampling is getting too expensive, we develop efficient simulation protocols of Artificial Intelligence accelerated Ab Initio Molecular Dynamics (AI2MD), enabled by the powerful Deep Potentials [5].

References

[1] J.-B. Le, M. Iannuzzi, A. Cuesta, J. Cheng*, Phys. Rev. Lett. 2017, 119, 016801.

[2] C.-Y. Li, J.-B. Le, J.-F. Li*, J. Cheng*, Z.-Q Tian, et al. Nature Mater. 2019, 18, 697.

[3] J.-J. Sun, J. Cheng*, Nature Commun. 2019, 10, 5400.

[4] J.-B. Le, Q.-Y. Fan, J.-Q. Li, J. Cheng*, Sci. Adv. 2020, 6, eabb1219.

[5] H. Wang, L. Zhang, J. Han, W. E, Computer Physics Communications 2018, 228, 178.

14:30 - 14:50
2.2-I2
Baker, L. Robert
The Ohio State University
Elucidating Charge and Spin Dynamics at Photochemical Interfaces Using Ultrafast XUV Spectroscopy
Baker, L. Robert
The Ohio State University, US
Authors
L. Robert Baker a
Affiliations
a, Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210 United States
Abstract

At the heart of photochemical energy conversion is the need to control charge and spin transport at catalytic interfaces. Many artificial systems rely on heterogenous catalysts to accomplish at surfaces what nature does using molecular assemblies, making it important to understand the material properties and surface states that mediate energy conversion. Despite its importance, the ability to directly probe charge and spin dynamics at surfaces on the ultrafast time scale with chemical-state resolution remains a significant challenge. Toward this goal, we have developed extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy.[1] This method combines the benefits of traditional X-ray absorption spectroscopy, such as element, oxidation, and spin state resolution, with surface sensitivity and ultrafast time resolution. Using this technique, we investigate charge and spin dynamics in materials with applications ranging from photocatalysis to optical control of magnetic switching. In one example, we describe a systematic comparison of surface and bulk electron polaron formation in hematite showing that surface self-trapping dynamics differ significantly from bulk and that these dynamics can be systematically tuned by surface molecular functionalization.[2] In a second example, we highlight evolving applications of XUV-RA spectroscopy to study spin dynamics at surfaces.[3] Applications include understanding ultrafast spin crossover in magnetic semiconductors as well as control of spin polarized electron dynamics at chiral photochemical interfaces.

14:50 - 15:10
Discussion
15:10 - 15:15
DSSC Break
15:10 - 15:15
PERIMPED Closing
15:10 - 15:20
SOLFUL Break
15:15 - 15:25
DSSC Session Introduction
15:20 - 15:30
SOLFUL Session Introduction 2.3
DSSC 2.3
Chair: Jared Delcamp
15:25 - 15:45
2.3-I1
Robertson, Neil
University of Edinburgh
Solid-state dye-sensitized solar cells: from organic HTMs to polyiodides
Robertson, Neil
University of Edinburgh, GB
Authors
Neil Robertson a, Ellie Tanaka a, Artit Jarusarunchai a, Matthew Sutton a, Wenjun Wu b
Affiliations
a, EaStCHEM School of Chemistry, University of Edinburgh, King’s Buildings, David Brewster Road, Scotland, UK
b, Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Shanghai Key Laboratory of Functional Materials Chemistry, School of Chemistry and Molecular Engineering, East China University of Science & Technology, 130 Meilon Road, Shanghai 200237, P. R. China
Abstract

High performance dye-sensitized solar cells (DSSC) over 7% power conversion efficiency (PCE) were first reported 30 years ago and involved a mesoporous TiO2 layer and a solution I-/I3- electrolyte. Slow recombination kinetics of the I-/I3- electrolyte makes it a favourable choice, however the volatile nature of the organic solvent has led to lower stability and therefore a focus on solid or quasi-solid hole transport materials. Organic hole-transport materials, such as spiro-OMeTAD, face challenges however, such as incomplete coverage of the thick mesoporous TiO2 network, requiring high absorption coefficient dyes to enable thin TiO2 layers. To this end, we have worked on series of strongly-absorbing organic dyes of simple design to minimise sensitiser costs, in keeping with potential practical application. We will report on our latest dyes, utilising simple thiophene and CPDT building blocks, used in both liquid and solid-state (spiro-OMeTAD) cells.

In a successful approach to move away from organic HTMs, Freitag et al. reported a “zombie” DSSC architecture where they slowly dried the copper complex electrolyte of a liquid-state DSSC until it transformed into a solid hole conductor. Recently, we have reported a solid-state DSSC that is fabricated by drying of the liquid I-/I3- electrolyte. We found that the liquid I-/I3- electrolyte (Liq-I) turns into a solid polyiodide hole transport material (Ply-I) by simply exposing the Liq-I to ambient air. Our initial studies show excellent stability of the solid-state polyiodide cells and initial work on rapid drying for practical fabrication are very promising.

15:45 - 16:05
2.3-I2
DEMADRILLE, Renaud
CEA Grenoble University
Organic dyes for robust and efficient semi-transparent solar cells and for devices with variable colours and self-adjustable optical transmission
DEMADRILLE, Renaud
CEA Grenoble University, FR
Authors
Renaud DEMADRILLE a, Johan LIOTIER a, Valid Mwatati MWALUKUKU a, Yann KERVELLA a, Pascale MAALDIVI a, Stéphanie NARBEY b, Frédéric OSWALD b, Antonio Jesus RIQUELME c, Juan Antonio ANTA c
Affiliations
a, CEA-Univ. Grenoble Alpes-CNRS, IRIG, SyMMES, 38000 Grenoble, France.
b, Solaronix SA, Aubonne, Switzerland
c, Área de Química Física, Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Sevilla, Spain
Abstract

In the last decade, the performances of emerging photovoltaic technologies integrating organic materials in the photoactive layer have continuously progressed. Among them, Dye-Sensitized Solar Cells (DSSC)s represent a promising approach both in terms of efficiency and production costs. These solar cells have recently demonstrated power conversion efficiencies (PCEs) over 14%, but more interestingly, they can be colourful and semi-transparent. For all these reasons, they are appealing for use Building-Integrated Photovoltaics (BIPV). [1]

In this communication, we will present the strategy followed at CEA-Grenoble to prepare robust, efficient and colourful organic photosensitizers. We will show that they can be used to fabricate solar cells combining high efficiency (over 10%) and outstanding stability over several years, and semi-transparent solar mini-modules [2-3-4]

Then, we will disclose our latest work on a new class of photochromic photosensitizers specifically designed for photovoltaic application. We will show that these molecules can be used to develop a new generation of functional solar cells capable to self-adjust their transparency and their photovoltaic energy conversion as a function of daylight intensity. [5]

16:05 - 16:25
2.3-I3
Hanson, Kenneth
Florida State University
Harnessing Molecular Photon Upconversion in Dye-Sensitized Solar Cells
Hanson, Kenneth
Florida State University, US

Kenneth Hanson received a B.S. in Chemistry from Saint Cloud State University (2005), his Ph.D. from the University of Southern California (2010), followed by an appointment as a postdoctoral scholar at the University of North Carolina at Chapel Hill (2010–2013). His independent research career began in 2013 at Florida State University as a member of the Department of Chemistry & Biochemistry and is affiliated with the Materials Science & Engineering program. His current research interests include the design, synthesis, and characterization of photoactive molecules/materials with particular emphasis on manipulating energy and electron-transfer dynamics at organic–inorganic interfaces using multilayer self-assembly.

 

Authors
Kenneth Hanson a, Yan Zhou a, Drake Beery a, Ashley Arcidiacono a
Affiliations
a, Florida State University, 95 Chieftan Way, Tallahssee, 32312, US
Abstract

Photon upconversion via triplet-triplet annihilation (TTA-UC) is the process of combining two or more low energy photons to generate a higher energy excited state. If harnessed in solar energy conversion, TTA-UC has the potential to increase the maximum theoretical solar cell efficiencies from 33% to greater than 43%. Recently, metal ion linked multilayer assemblies on TiO2 has emerged as an effective strategy to not only facilitate TTA-UC but also harness it in a dye-sensitized solar cell (DSSC). In this presentation we will recount our groups recent progress in integrating these TTA-UC multilayers directly into DSSCs and how compositional and structural variation influences the upconverted photocurrent generation.  This includes QD sensitized bilayers and singlet sensitized trilayers. We will also describe our efforts to understand the role of the molecular and bilayer structure in dictating the efficiency of energy/electron transfer, TTA, and photocurrent generation.

16:25 - 16:45
Discussion
15:30 - 15:35
CHEMNC Break
15:30 - 15:40
NanoLight Session 2.3 Introduction by Sascha Feldmann
SOLFUL 2.3
Chair not set
15:30 - 15:50
2.3-I1
Wang, Shu
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China
Photosynthetic organic semiconductor biohybrid systems for solar-to-chemical conversion
Wang, Shu
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China, CN
Authors
Shu Wang a
Affiliations
a, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China, Beijing, CN
Abstract

Photosynthetic biohybrid systems could realize the solar-to-chemical conversion by taking advantage of light-harvesting ability of semiconductors and the synthetic ability of biological cells. However, high-performance photosynthesis requires good solar energy utilization, hole/electron separation efficiency and the electron transfer between the semiconductor and biological cells, which has been challenging to achieve with the systems used so far. We developed a biohybrid photosynthetic system through coating organic semiconductors onto the surface of Moorella thermoacetica. This system can efficiently realize CO2 reduction to produce acetic acid. Both cationic electron-transporting (n-type) perylene diimide derivative (PDI) and hole-transporting (p-type) poly(fluorene-co-phenylene) (PFP) act as the excellent photosensitizers. The PFP/PDI p-n heterojunction layer forms on the bacteria surface. The bacteria can harvest photoexcited electrons from PFP/PDI layer. The electrons can drive the metabolism pathway to synthesize acetic acid from CO2 under light illumination. The efficiency of 1.6 % is comparable to those of reported biohybrid systems. Very recently, we have found a synthetic light-harvesting polymer [poly(boron-dipyrromethene-co-fluorene) (PBF)] with green light absorption and far-red emission could improve PSI activity of algae Chlorella pyrenoidosa (C. pyrenoidosa), followed by further upgrading PSII activity to augment natural photosynthesis. For light-dependent reactions, PBF accelerated photosynthetic electron transfer in the electron transport chain, and the productions of oxygen, ATP and NADPH were increased by 120%, 97% and 76%, respectively. For light-independent reactions, the Rubisco activity in algae was enhanced by 1.5-fold, while the expression levels of rbcL encoding Rubisco and prk encoding phosphoribulokinase were up-regulated by 2.6 and 1.5-fold, respectively. Consequently, the C. pyrenoidosa growth was accelerated by 1.1-fold with the increase of lipids and proteins contents by 36% and 60%, respectively. Furthermore, we demonstrated that polymer PBF could be absorbed by the Arabidopsis thaliana (A. thaliana) to speed up cell mitosis and enhance photosynthesis, ultimately promoting its growth and flowering. By improving the efficiency of natural photosynthesis, synthetic light-harvesting polymer materials show promising potential applications for biofuel production, as well as for future energy and environmental development.

15:50 - 16:10
2.3-I2
Reisner, Erwin
University of Cambridge - UK
Artificial Leaves, Sheets and Panels For Solar Fuel Synthesis
Reisner, Erwin
University of Cambridge - UK, GB

Erwin Reisner received his education and professional training at the University of Vienna (with Prof Bernhard K. Keppler), the Massachusetts Institute of Technology (with Prof Stephen J. Lippard) and the University of Oxford (with Prof Fraser A. Armstrong) before starting his independent career as a University Lecturer at Cambridge and Fellow of St. John’s College in 2010. He holds an EPSRC Career Acceleration Fellowship and heads the Christian Doppler Laboratory for Sustainable SynGas Chemistry. His group develops artificial photosynthesis by combining chemical biology, synthetic chemistry and materials chemistry.

Authors
Erwin Reisner a
Affiliations
a, Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Abstract

Artificial leaves, photocatalyst panels and sheets mimic plant leaves in form and function as they are thin panels fabricated in the laboratory powered by sunlight to produce sustainable energy carriers.1-3 This presentation will give an overview of our recently assembled prototype systems for the conversion of water and the greenhouse gas carbon dioxide into gaseous and liquid fuels as well as the decomposition of biomass and plastics waste into green hydrogen.4-6 The idea and concept behind these integrated thin film devices for solar energy conversion and the relevance of these systems to secure and harness sustainable energy supplies in a fossil-fuel free economy will be discussed.

16:10 - 16:30
2.3-I3
Gu, Jing
San Diego State University
The Water-Energy Nexus: Microbial Photoelectrochemical Conversion for Solar Fuel Generation and Wastewater Treatment
Gu, Jing
San Diego State University, US

Professor Gu's research focuses on designing novel solid-state and hybrid electrocatalysts for fuel generation, along with investigating and tailoring charge transfer mechanisms at the semiconductor-catalyst interface for solar energy conversion reactions, such as CO2 reduction, water oxidation, and water reduction.

Authors
Jing Gu a, Lu Lu b, Zhida Li a, Jason Ren b
Affiliations
a, San Diego State University, Campanile Drive, 5500, San Diego, US
b, Princeton University, Dept. Electrical Engineering, Princeton , 8540, US
Abstract

The water-energy nexus is rooted in the fact that water and energy are interdependent systems. All stages of energy production utilize water. Likewise, energy is necessary to desalinate, treat, and distribute clean water. Inevitable changes related to population growth, weather, and the environment affect the relationship between our natural resources and energy infrastructure. These challenges induce vulnerabilities within our nation’s population and increase the urgency for action. Therefore, an integrated approach that addresses both the challenges and opportunities of the water-energy nexus carries great potential in providing solutions for these impending circumstances.

Artificial photosynthesis (APS) mimics nature by photoelectrochemically generating clean energy from water and sunlight. Challenges faced by current APS systems involve high costs, low efficiencies, and short lifetimes. Furthermore, most APS devices rely on clean water sources, limiting their potential for impact. In this study, we developed an inexpensive, nanostructured black silicon photocathode exhibiting a “swiss-cheese” interface coupled to an electroactive microbial bioanode that efficiently produces clean energy from real brewery wastewater continuously for over 90 hours. Sourcing brewery wastewater reduces associated costs and provides a microbe-driven voltage boost that increases device efficiency in the absence of an external bias. Generating clean energy from concurrent wastewater treatment provides ideal solutions to the challenges faced by our nation and its energy infrastructure.

16:30 - 16:50
Discussion
15:35 - 15:45
CHEMNC Session Introduction 2.3
NanoLight 2.3
Chair: Sascha Feldmann
15:40 - 16:00
2.3-I1
Rand, Barry
Princeton University
Proper thermal management allows for brighter metal halide perovskite light emitting diodes
Rand, Barry
Princeton University, US
Authors
Barry Rand a
Affiliations
a, Princeton University, Department of Electrical Engineering & the Andlinger Center for Energy and the Environment
Abstract

Hybrid organic-inorganic halide perovskite materials are promising for light emitting applications. In this talk, I will discuss our recent work on perovskite-based LEDs, where we have established a general protocol for preparing ultrathin, smooth, passivated, and pinhole free films of metal halide perovskites with various compositions, by incorporating bulky organoammonium halide additives to the stoichiometric 3D perovskite precursors. In addition, we have found that a major factor contributing to roll-off of perovskite LEDs is heating. By avoiding heating through numerous strategies, we are able to reduce roll-off and report record-bright perovskite LEDs, pushing toward display, lighting, and even lasing-relevant current densities.

16:00 - 16:20
Abstract not programmed
16:20 - 16:40
2.3-I2
Utzat, Hendrik
Stanford University
Fast Interferometric Spectral Diffusion Measurements of Emerging Single-Photon Emitters
Utzat, Hendrik
Stanford University, US
Authors
Hendrik Utzat a, Weiwei Sun b, Bors Spokoyny b, Alexander Kaplan b, Moungi Bawendi b
Affiliations
a, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
b, Massachusetts Institute Of Technology (MIT), Department of Chemistry, Massachusetts Avenue, 77, Cambridge, US
Abstract

Spectral diffusion is a ubiquitous process caused by bath fluctuations which randomizes the spectral mode of single-photon emitters at cryogenic temperatures. Accurately measuring spectral diffusion on a single-emitter level is still a challenging task owing to the required high spectral and temporal resolution with an additionally high temporal dynamic range. As a direct consequence, spectral diffusion and the underlying exciton-bath interaction are poorly understood for most emerging single-photon emitters.

In this talk, we highlight our recent progress towards understanding spectral diffusion in nascent quantum emitters using photon-correlation Fourier spectroscopy (PCFS). PCFS can measure the bandwidth and kinetics of spectral fluctuations down to nanosecond timescales. Using PCFS, we show how quantum emitters in 2D hexagonal boron nitride exhibit multi-timescale discrete spectral jumping that can be attributed to a bath with at least two characteristic fluctuation relaxation times.[1] Analysis of colloidal perovskite quantum dots at low temperatures reveals that different emissive fine-structure states are coupled to the same bath fluctuations and exhibit correlated diffusion dynamics.[2] Broadly, we propose PCFS as a particularly suitable tool for the detailed study of decoherence processes and spectral diffusion occurring over many orders of magnitude in the temporal domain.

16:40 - 17:00
Discussion
CHEMNC 2.3
Chair: Loredana Protesescu
15:45 - 16:05
2.3-I1
Rossini, Aaron
Iowa State University, USA
Surface Characterization of CdSe Nanoparticles and Nanoplates by Dynamic Nuclear Polarization 77Se and 113Cd Solid-State NMR Spectroscopy
Rossini, Aaron
Iowa State University, USA
Authors
Yunhua Chen a, b, Rick Dorn a, b, Michael Hanrahan a, b, Lin Wei b, Marquix Adamson b, Rafael Blome-Fernandez b, Javier Vela b, Aaron Rossini a, b
Affiliations
a, US DOE Ames Laboratory, Ames, Iowa, USA, 50011
b, Iowa State University, Department of Chemistry, Ames, Iowa, USA, 50011
Abstract

Nanocrystals (NCs) have emerged as next-generation materials for optoelectronic devices, catalysis and biological imaging. Due to their high surface area to volume ratio, the surface structure of nanocrystals strongly impacts their optical and electrical properties. However, techniques that can provide detailed surface structure are lacking. Here, we show how dynamic nuclear polarization (DNP) solid-state NMR spectroscopy can be used to obtain detailed surface structures of some of the most widely investigated nanocrystals, zinc blende CdSe NCs with spheroidal and plate morphologies. 1D 113Cd and 77Se cross-polarization magic angle spinning (CPMAS) NMR spectra reveal distinct signals from Cd and Se atoms on the surface of the nanoparticle, and those residing in bulk-like environments below the surface. 113Cd magic-angle-turning (MAT) experiment identifies CdSe3O and CdSeO3 coordination environments from {111} facets and CdSe2O2 coordination environments from {100} facets, where the oxygen atoms are from coordinated oleate ligands.  The sensitivity gains from DNP enables acquisition of natural isotopic abundance 2D homonuclear 113Cd and 77Se and heteronuclear 113Cd-77Se correlation solid-state NMR experiments. Scalar double-quantum single-quantum 2D homonuclear 113Cd and 77Se correlation spectra reveal the connectivity of the surface and core Cd and Se atoms. Importantly, scalar heteronuclear 77Se{113Cd} multiple quantum coherence (J-HMQC) experiments illustrate the connection between the various Cd and Se environments and can be used to selectively measure one-bond 113Cd-77Se scalar coupling constants (1JSe-Cd). With knowledge of 1JSe-Cd, heteronuclear 77Se{113Cd} spin echo (J-resolved) NMR experiments are then used to determine the number of Se atoms bonded to Cd atoms, and vice versa. The J-resolved experiments directly confirm that major Cd and Se surface species have CdSe2O2 and SeCd4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe, we conclude that the surface of the spheroidal CdSe nanocrystals is primarily composed of {100} and {111} facets. The methods outlined here will be generally applicable to obtain detailed surface structures of a wide variety of main group semiconductors.

16:05 - 16:25
2.3-I2
Milliron, Delia
The University of Texas at Austin
Gel Assemblies of Colloidal Nanocrystals
Milliron, Delia
The University of Texas at Austin, US
Authors
Delia Milliron a
Affiliations
a, McKetta Department of Chemical Engineering, University of Texas at Austin, 200 E. Dean Keeton St, Austin, TX, 78712, US
Abstract

Controlling the arrangement of inorganic nanocrystals in gel assemblies allows realization of materials whose properties depend both on the distinct characteristics of their nanoscale building blocks and on their organization. However, nanocrystal gels have been formed mostly through irreversible aggregation, which limits control over structure. We have developed reversible gelation strategies based on guidance from theoretically predicted phase diagrams, opening the door to both structural control and switchable properties. Using doped metal oxide nanocrystals as building blocks, we demonstrated that infrared absorption is reversibly modulated by assembly, owing to coupling between their localized surface plasmon resonance when networked in gels.

16:25 - 16:45
2.3-I3
Lindenberg, Aaron
Department of Materials Science and Engineering, Stanford University
Photoinduced structural response of nanomaterials probed by femtosecond diffraction techniques
Lindenberg, Aaron
Department of Materials Science and Engineering, Stanford University, US
Authors
Aaron Lindenberg a
Affiliations
a, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
Abstract

I will describe recent experiments using femtosecond electron diffraction approaches to obtain structural snapshots of light-induced processes in semiconductor nanocrystals.  In the first part of the talk I will describe how one can visualize for the first time the transient lattice deformations accompanying radiationless electronic processes in core-shell quantum dots.  Investigation of the excitation energy dependence shows that hot carriers created by a photon energy considerably larger than the bandgap induce structural distortions at nanocrystal surfaces on few picosecond timescales associated with the localization of trapped holes. On the other hand, carriers created by a photon energy close to the bandgap result in transient lattice heating that occurs on a much longer 200 ps timescale, governed by an Auger heating mechanism. Elucidation of the structural deformations associated with the surface trapping of hot holes provides atomic-scale insights into optoelectronic performance and a pathway towards minimizing these losses in nanocrystal devices.  In the second part of the talk I will discuss application of similar techniques to hybrid perovskite nanocrystals, probing the structural responses associated with exciton-lattice coupling in FAPbBr3 and CsPbBr3 nanocrystals

16:45 - 17:05
Discussion
16:45 - 16:50
DSSC Closing
16:50 - 16:55
Closing SOLFUL
17:00 - 17:05
NanoLight Closing
17:00 - 18:00
Power Hour for Mentorship
17:05 - 17:10
CHEMNC Closing
18:00 - 19:00
"Happpy Hour" Life as a PhD candidate is so full of stress. What should I do?
 
Thu Mar 11 2021
10:30 - 10:35
ORGELE Opening nanoGe
10:30 - 10:35
PEREMER Opening nanoGe
10:30 - 10:35
PEROPV Opening nanoGe
10:30 - 10:35
SEFLNC Opening nanoGe
10:30 - 10:35
UPDOWN Opening nanoGe
10:35 - 10:45
ORGELE Session Introduction 1.1
10:35 - 10:45
PEREMER Session Introduction 1.1
10:35 - 10:45
PEROPOV Session Introduction
10:35 - 10:45
SELFNC Session Introduction 1.1
10:35 - 10:45
UPDOWN Session Introduction 1.1
ORGELE 1.1
Chair: Emrys Evans
10:45 - 11:05
1.1-I1
Friend, Richard
University of Cambridge - UK
Radical organic semiconductors for light emission
Friend, Richard
University of Cambridge - UK, GB

Richard Friend holds the Cavendish Professorship of Physics at the University of Cambridge. His research encompasses the physics, materials science and engineering of semiconductor devices made with carbon-based semiconductors, particularly polymers. His research advances have shown that carbon-based semiconductors have significant applications in LEDs, solar cells, lasers, and electronics. His current research interests are directed to novel schemes – including ideas inspired by recent insights into Nature’s light harvesting – that seek to improve the performance and cost of solar cells.

Authors
Richard Friend a
Affiliations
a, Optoelectronics Group, University of Cambridge, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Abstract

We and others have recently reported that certain classes of radical organic semiconductors can be used as efficient light emitters in LED devices. Excitation within the doublet manifold can avoid the formation of non-emissive higher spin states and therefore allow efficient radiative electron-hole recombination [1]. We have found that structures where the lowest double excited state involves promotion of an electron from a HOMO level associated with a donor moiety such as carbazole to the radical SOMO level can show very high luminescence yield [2], and we have optimised structures so that it is possible to electrically excite this doublet state, by sequential charge transfer of electron and hole[1], taking account of the Coulomb charging energy for double occupancy of the SOMO [3]. I will present recent work where we use the radical semiconductor as the emissive ‘guest’ in a regular organic LED emissive layer ‘host’ where the radical semiconductor is able to harvest both singlet and triplet excitons formed in the host material.

11:05 - 11:25
1.1-I2
Li, Feng
Jilin University
Luminescence Radicals with Electronic Structure Not Following the Aufbau Principle
Li, Feng
Jilin University, CN

Feng Li completed his PhD studies at Jilin University in 2003, followed by postdoctoral studies at Technion-Israel Institute of Technology. Then he returned to Jilin University in 2005 as an Associate Professor of Chemistry and promoted to full Professor in 2008. From 2017 to 2019, He was an Academic Visitor of Cavendish Laboratory, University of Cambridge. His research focuses on organic optoelectronic materials and devices based on some new concepts, for example the OLEDs in which the emission comes from doublet exciton. In 2019, He won the National Science Fund for Distinguished Young Scholars of China.

Authors
Feng Li a
Affiliations
a, State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University
Abstract

Due to the single unpair electron in mono-radical materials, the spin configurations of their excited states and ground state are both doublets. So, the emission process is spin-allowed. We exploited a luminescent radical, TTM-1Cz, as the emitter to fabricate the first OLED with doublet emission. The problem caused by the spin-forbidden transition of triplet exciton in traditional fluorescent OLEDs is circumvented. 1 After continually optimizing materials and device, an OLED with a maximum external quantum efficiency beyond the spin-statistic limit was obtained.2

We found a series of light-emitting radicals whose electronic structures do not following the Aufbau Principle, which means the singly occupied molecular orbital(SOMO) lies below the doubly occupied highest occupied molecular orbital(HOMO). The quasi-close-shell character enhances the stability of the radicals remarkably and maintains high luminescent efficiency simultaneously, which may offer a feasible route to address the stability issue of luminescent radicals 3

11:25 - 11:45
1.1-I3
Crivillers, Núria
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
Organic radicals as promising building blocks for molecular electronics
Crivillers, Núria
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain, ES
Authors
Núria Crivillers a, Jesús Alejandro de Sousa a, Marta Mas-Torrent a, Concepció Rovira a, Jaume Veciana a, Bruno Fabre b
Affiliations
a, Intitute of Materials Science of Barcelona (ICMAB-CSIC)
b, UMR Univ. Rennes 1/CNRS 6226, Institut des Sciences Chimiques de Rennes
Abstract

In recent decades, the robust molecular modification of surfaces has been a determining factor for progressing in the development of molecular electronic devices.[1] Gold and more recently carbon based substrates decorated with functional small molecules have awakened much interest for sensing, biological, optoelectronic, molecular (spin)electronics, and catalytic applications. Among other molecular electroactive systems, we are especially interested in studying stable organic radicals. Nowadays, these materials have attracted much interest and their exploitation as components of molecular functional materials is boosting a new generation of devices for applications in OLEDs, energy storage and conversion, molecular spintronics, imaging, sensors and memory devices.[2] Perchlorinated triphenylmethyl (PTM) radicals are a class of persistent organic radicals that are chemically and thermally persistent redox and magnetically active species. Being all-organic, PTM radicals present an intrinsic magnetic moment, low spin−orbit coupling and low hyperfine interactions. These radicals have been nanostructured on surface as nanometer thick films, self-assembled monolayers and in single-molecule junctions, employing substrates of different nature such as gold, indium-tin oxide, sp2-carbon substrates and more recently on p-type Si-H.[3] The charge transport measurements through PTM radicals films and at the single molecule level have elucidated the key role of the unpaired electron on the device performance. Regarding the use of SAMs, currently, further progress is hindered by the modest stability and reproducibility of the molecule/electrode contact. For this, by exploiting the rich chemistry, in solution and on surface, offered by alkynes (-C≡CH) and the high chemical and thermal stability of PTM radicals, the magnetic and redox properties of a PTM radical bearing one and two terminal alkyne groups has been dually exploited on SiO2-free silicon and on gold to prepare capacitance switches. Furthermore, a novel PTM organic free radical containing an aryl diazaonium salt has been synthesized and employed to modify carbon-based substrates (HOPG, graphene oxide, carbon nanotubes) leading to a new range of applications in optoelectronic and sensing devices.

11:45 - 12:05
Discussion
PEREMER 1.1
Chair: Simon Kahmann
10:45 - 11:05
1.1-I1
Quarti, Claudio
University of Mons, Centre d'Innovation et de Recherche en Matériaux Polymères (CIRMAP)
From symmetry-analysis to full atomistic detail: getting a big picture of the optical properties of layered halide perovskites
Quarti, Claudio
University of Mons, Centre d'Innovation et de Recherche en Matériaux Polymères (CIRMAP), BE
Authors
Claudio Quarti a
Affiliations
a, University of Mons, Laboratory for Chemistry of Novel Materials, B-7000 Mons, Belgium
Abstract

Dimensionally confined, layered metal halide perovskites are natural quantum-well nano-architectures, where the band gap of the inorganic metal-halide sheets is embedded into that of insulating organic spacers. The optical properties of these systems are as fascinating as complex,[1] characterized by several features, sometimes in apparent contrast, as the coexistence of two emission signatures, namely the ubiquitous narrow bandwidth/small-Stokes shifted one and a broadband emission. In this sense, a “big picture” is needed, that may reconcile these and other features, peculiar for layered halide perovskite compounds, at once.

Starting from very naïve question, “how the dimensional confinement modifies the electronic properties of metal-halide frames”, I will make use of general symmetry analysis to discuss the differences between the electronic structure of 2D systems, compared to their 3D frames, also accounting for Spin-Orbit Coupling. Considering the main role of strongly bound excitons on the optical properties of these systems, I will extend the symmetry analysis to the fine structure of the exciton ground state, with reference to experimental results from spectroscopy and predictions from accurate simulations based on the ab-initio solution of the Bethe-Salpeter Equation.[2] In the effort of including additional ingredients to the optical response of metal halide perovskites, I will discuss the role of lattice deformations and ionic defects. With special focus on broadband emission, I will give an overview of the proposed defect- and polaron- related mechanisms,[3-4] especially in relation to the reduced polaron relaxation energies (~ meV) reported in the literature.[5]

Time permitting, I will briefly discuss layered perovskite compounds, incorporating organic chromophores as spacers. Substitution of commonly employed, electronic inert organic spacers with molecules featuring extended p-conjugation allows to pass from type I to type II electronic interface,[6] which paves the way for a plethora of charge and energy transfer at the organic/inorganic interface. Charge and energy transfer mechanisms in these hybrids however are comparably less understood, if compared to long-established fields of molecular electronics [7] or biology [8]. Proper usage of terms like Forster-like single-singlet and Dexter-like triplet-triplet energy transfer models will be discussed for halide perovskite systems, where Spin-Orbit-Coupling cannot be neglected.

11:05 - 11:25
1.1-I2
Xiong, Qihua
Tsinghua University
Bright Excitons in Two-Dimensional Layered Lead Halide Perovskite Semiconductors
Xiong, Qihua
Tsinghua University, CN
Authors
Qihua Xiong b, T. Thu Ha Do a, Sheng Liu a
Affiliations
a, NTU Singapore - Nanyang Technological University, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Link, 21, Singapore, SG
b, Tsinghua University, Yifu Building Room 2422, Tsinghua University,Haidian District, Beijing, 100084, CN
Abstract

Research on lead halide semiconductors with perovskite lattices is a rapidly growing field in nanoscience and semiconductor physics. Their optical properties can be tuned by tailoring the chemical composition and/or the nanostructure spatial dimension with very high precision and high quality [1]. Especially, in two-dimensional perovskites where the inorganic framework is sandwiched between two organic layers, coupled electron-hole pairs (excitons) are strongly confined within atomically thin quantum-wells with large binding energies of ~200 meV under spatial and dielectric confinement. Moreover, the hybrid nature and soft lattice of organic-inorganic lead halide perovskites render their structural changes and optical properties susceptible to external driving forces such as temperature and pressure, remarkably different from conventional semiconductors.  

 

Herein, we study the optical properties of high-quality two-dimensional perovskite crystals by using external stimuli such as pressure, temperature and magnetic field. We resolve an extraordinary fine-structure splitting of bright excitons of up to ~2 meV, which is the largest value in two-dimensional semiconducting systems [2]. The large fine-structure splitting is attributed to the strong electron-hole exchange interaction in layered perovskites, which is proved by the optical emission in high magnetic fields of up to 30 Tesla. On the other hand, by applying a moderate pressure of below 3.5 GPa, the optical spectra exhibit a large tunability of up to 320 meV, while the quantum-yield remains constant [3]. Such a large tunable range originates from the anisotropic structural deformation that effectively modulates the quantum confinement effect by 250 meV via barrier height lowering. Moreover, due to the large binding energy and oscillator strengths, two-dimensional perovskites are ideal candidates for studying strong light-matter interaction [4]. We successfully demonstrate room-temperature strong coupling in exfoliated 2D perovskite semiconductors embedded into a planar microcavity, exhibiting a large energetic splitting-to-linewidth ratio of 34.2. Our findings advocate a considerable promise of 2D perovskite to explore not only fundamental optical properties but also quantum phenomena such as Bose-Einstein condensation, superfluidity and exciton-polariton networks.

11:25 - 11:45
1.1-I3
Plochocka, Paulina
Laboratoire National des Champs Magnétiques Intenses, CNRS
Excitons and Phonons in 2D perovskites
Plochocka, Paulina
Laboratoire National des Champs Magnétiques Intenses, CNRS, FR

Paulina Plochocka, Directrice de recherché de 2e classe (DR2) in Laboratoire National des Champs Magnétiques Intenses (LNCMI), CNRS in Toulouse.

P. Plochocka obtained her PhD cum-laude in 2004 at the University of Warsaw working on the dynamics of many-body interactions between carriers in doped semi-magnetic quantum wells (QW). During her first post doc at Weizmann Institute of science, she started working on the electronic properties of a high mobility 2D electron gas in the fractional and integer quantum Hall Effect regime. She continued this topic during second post doc in LNCMI Grenoble, where she was holding individual Marie Curie scholarship. At the same time, she enlarged her interest of 2D materials towards graphene and other layered materials as TMDCs or black phosphorus. In 2012 she obtained permanent position in LNCMI Toulouse, where she created the Quantum Electronics group, which investigates the electronic and optical properties of emerging materials under extreme conditions of high magnetic field and low temperatures. Examples include semiconducting layer materials such as transition metal dichalcogenides, GaAs/AlAs core shell nanowires and organic inorganic hybrid perovskites.

Authors
Paulina Plochocka a
Affiliations
a, Laboratoire National des Champs Magnetiques Intenses, CNRS-UJF-UPS-INSA, Toulouse, France
b, Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
Abstract

High environmental stability and surprisingly high efficiency of solar cells based on 2D perovskites have renewed interest in these materials. These natural quantum wells consist of planes of metal-halide octahedra, separated by organic spacers.  Remarkably the organic spacers play crucial role in optoelectronic properties of these compounds. The characteristic for ionic crystal coupling of excitonic species to lattice vibration became particularly important in case of soft perovskite lattice. The nontrivial mutual dependencies between lattice dynamics, organic spacers and electronic excitation manifest in a complex absorption and emission spectrum which detailed origin is subject of ongoing controversy. First, I will discuss electronic properties of 2D perovskites with different thicknesses of the octahedral layers and two types of organic spacer.  I will demonstrate that the energy spacing of excitonic features depends on organic spacer but very weakly depends on octahedral layer thickness. This indicates the vibrionic progression scenario which is confirmed by high magnetic fields studies up to 67T. Finally, I will show that in 2D perovskites, the distortion imposed by the organic spacers governs the effective mass of the carriers.  As a result, and unlike in any other semiconductor, the effective mass in 2D perovskites can be easily tailored.  

11:45 - 12:05
Discussion
PERPOV 1.1
Chair not set
10:45 - 11:05
1.1-I1
Catchpole, Kylie
Australian National University
Passivation approaches for high efficiency perovskites
Catchpole, Kylie
Australian National University, AU

Kylie Catchpole is Professor in the Research School of Engineering at the Australian National University.  She has over 100 scientific publications, with a focus on using new materials and nanotechnology to improve solar cells.  She completed her PhD at ANU and was a postdoctoral fellow at the University of New South Wales and the FOM Institute for Atomic and Molecular Physics in Amsterdam before returning to ANU in 2008.  In 2013 she was awarded a Future Fellowship from the Australian Research Council and in 2015 she was awarded the John Booker Medal for Engineering Science from the Australian Academy of Science. 

Authors
Kylie Catchpole a
Affiliations
a, Australian National University, Engineering Building 32, Room 222, Canberra, 2601, AU
Abstract

An essential approach to improve efficiency of perovskite photovoltaics is passivation of the interfaces.  We demonstrate a 4-terminal tandem perovskite/silicon configuration in which the efficiency is as high as 27.7% through a passivation approach using 2D perovskites.   We also demonstrate efficiency above 21% and fill factor of 83% for a 1cm2 single junction perovskite cell using a nanotextured electrode transport layer, and we explain how passivation contributes to the high fill factor observed in these devices.  Finally we demonstrate a novel 2D passivation scheme for 3D perovskite solar cells using a mixed cation composition of 2D perovskite based on two different isomers of butylammonium iodide. The dual‐cation 2D perovskite outperforms its single cation 2D counterparts in surface passivation quality, resulting in devices with an impressive open‐circuit voltage of 1.21 V for a perovskite composition with an optical bandgap of 1.6 eV, and a champion efficiency of 23.3%.  These results show the clear benefits of passivation of perovskites for practical high efficiency devices.

11:05 - 11:25
1.1-I2
Seok, Sang Il
Ulsan National Institute of Science and Technology (UNIST)
Achieving High-Efficiency FAPbI3 Perovskite Solar Cells with Cation Management
Seok, Sang Il
Ulsan National Institute of Science and Technology (UNIST), KR

Sang Il Seok is currently a Distinguished Professor at the School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Korea. Before he joined UNIST in 2015, he served on the principle investigater of Korea Research Institute of Chemical Technology and professor at department of energy science, Sungkyunkwan University. In 2017, he was appointed as guest professor of Nankai University in China. He obtained his PhD degree at Department of Inorganic Materials Engineering of Seoul National University, Korea, in 1995. From 1996 to 1997, he experienced a post-doc to investigate defects and transport in Fe-Ti-O Spinel structure in Cornell University, USA, and visiting scholar in University of Surrey, UK, in 2003, and École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, in 2006 respectively. His major research interests were functional inorganic-organic hybrid materials through solution process for optical amplifier, high dielectrics, corrosion-resistance coatings etc. Now, his research focus is based on inorganic-organic hybrid solar cells, in particular perovskite solar cells. He published more than 150 peer-reviewed papers including Nature, Science etc. with several awards for his Excellency.

Authors
Sang Il Seok a
Affiliations
a, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan. Korea
Abstract

The fabrication of high-efficiency perovskite solar cells is in principle very simple. A high-efficiency device could be produced if the interfacial recombination loss between heterogeneous thin films including charge-transporting layers can be reduced and fast charge transfer can be maintained with perovskite light absorbers of an optimal band gap. However, the efficiency of a real perovskite device is very sensitively dependent on several conditions such as precursor solution, coating method, type of charge carrier, and interfacial state. Among these conditions, I would like to present the results obtained recently through the managed cations in the FAPbI3 perovskite layer. For example, we incorporated the same molar ratio of two cations (cesium (Cs) and methylenediammonium (MDA) cations to stabilize the a phase of the FAPbI3 perovskite. The optimized amount of Cs+ and MDA2+ reduced the lattice strain and trap densities, which resulted in enhanced Voc and reproducible PCEs. The best performing PSC showed a PCE > 25% (24.4% certified) for the small device and 21.63% (certified) for a large area (1x1 cm2).

 

11:25 - 11:45
1.1-I3
Liu, Shengzhong
Shaanxi Normal University
High Efficiency Perovskite Solar Cells
Liu, Shengzhong
Shaanxi Normal University, CN

Professor Shengzhong (Frank) Liu received his PhD from Northwestern University in 1992. Upon completing his postdoctoral research at Argonne National Laboratory in 1994, he joined high-tech industrial research, most notably on solar cells with Solarex/BP Solar and United Solar Ovonic. His research focuses on perovskite solar cells, optoelectronic devices, single-crystalline perovskite materials, high efficiency HIT solar cells, nanoscale thin film materials and photocatalyst for photoelectrochemical water splitting. He has published more than 100 papers in peer-reviewed journals including Science, Nature, Nature Communications, Energy & Environ. Sci., Adv. Mater., Sci. Adv., Phys. Rev. X. He was recruited into the Chinese National “1000-Talent Program”in 2011 and now he is a professor at Shaanxi Normal University and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

Authors
Shengzhong Liu a, b, Minyong Du a, Xuejie Zhu b, Kai Wang a, Hui Wang a, Yuxiao Jiao a, Yuexian Cao a, Likun Wang a, Xiao Jiang a, Lianjie Duan a, Youmin Sun a
Affiliations
a, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P.R. China, Dalian, CN
b, Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science & Engineering, Shaanxi Normal University, Xi'an 710119, P.R. China
Abstract

A new type organic-inorganic hybrid perovskite has appeared to be a wonder material for its excellent optical absorption, long range charge-carrier diffusion and apparent tolerance to defects. In the last few years, it has been emerged as a primary candidate material for various photovoltaic, optoelectronic and photoelectronic applications. In just a few years, its solar cell efficiency has been improved from 3.8% to >25%. Moreover, the solar cell fabrication processes based on the planar architecture have been particularly enthusiastic thanks to their low temperature fabrication and compatibility with a range of substrates. Comparing solution deposition with vacuum deposition, the vacuum processes for thermal co-deposition and sequential deposition of PbCl2 and CH3NH3I materials are recognized as efficient means to prepare perovskite film with good uniformity and high surface coverage. A vacuum deposition process has been developed to fabricate high efficiency perovskite solar cells with high stability using alternating layer-by-layer vacuum deposition. The new deposition process allows us to relax the strict deposition monitoring and control measures, while realizing superior uniformity in film morphology, surface coverage and smoothness, together with crystalline phase purity.

For the high efficiency perovskite solar cells, the power conversion efficiencies for the planar device is as high as 23.4%. More importantly, we have developed a superior low temperature modified SnO2 material for ETL and transferred the cell fabrication process onto lightweight flexible polymeric substrate. The highest cell efficiency achieved was over 20%, it is also the highest efficiency among the flexible perovskite cells reported. Meanwhile, the devices show very good stability over long term exposure in ambient with very low degradation. After a representative cell was exposed in ambient lab condition for a year, its final cell efficiency is as high as over 95% of its initial efficiency with its degradation accounts for only smaller than 5%. Further analysis on the stability of the perovskite solar cells will be discussed. We have also developed a series of single-crystalline perovskites with superior stability and optoelectronic performance.

11:45 - 12:05
Discussion
SELFNC 1.1
Chair: Dmitry Baranov
10:45 - 11:05
1.1-I1
Na Liu, Laura
University of Stuttgart
Functional DNA nanotechnology
Na Liu, Laura
University of Stuttgart, DE

Laura Na Liu is a full professor at the Kirchhoff Institute for Physics at University of Heidelberg, Germany. She received her Ph. D in Physics at University of Stuttgart in 2009, working on 3D complex plasmonics at optical frequencies. In 2010, she worked as postdoctoral fellow at the University of California, Berkeley. In 2011, she joined Rice University as Texas Instruments visiting professor. At the end of 2012, she obtained a Sofja Kovalevskaja Award from the Alexander von Humboldt Foundation and became an independent group leader at the Max-Planck Institute for Intelligent Systems. She joined University of Heidelberg in 2015. Her research interest is multi-disciplinary. She works at the interface between nanophotonics, biology, and chemistry. Her group focuses on developing sophisticated and smart optical nanosystems for answering structural biology questions as well as catalytic chemistry questions in local environments.

Authors
Laura Na Liu a, b
Affiliations
a, 2nd Physics Institute, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
b, Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
Abstract

A fundamental design rule that nature has developed for biological machines is the intimate correlation between motion and function. One class of biological machines is molecular motors in living cells, which directly convert chemical energy into mechanical work. They coexist in every eukaryotic cell, but differ in their types of motion, the filaments they bind to, the cargos they carry, as well as the work they perform. Such natural structures offer inspiration and blueprints for constructing DNA-assembled artificial systems, which mimic their functionality. In this talk, I will discuss a variety of DNA-assembled architectures with different motion and functions. I will also outline ongoing research directions and conclude that DNA nanotechnology has a bright future ahead.

11:05 - 11:25
1.1-I2
Dijkstra, Marjolein
Debye Institute for Nanomaterials Science
Structuring Matter over Multiple Length Scales using Self-Assembly in Spherical Confinement: Crystals of Crystals of Nanocrystals
Dijkstra, Marjolein
Debye Institute for Nanomaterials Science, NL

 

Marjolein Dijkstra is full professor (2007) in the Debye Institute for Nanomaterials Science at Utrecht University. She received a MSc degree in Molecular Sciences at Wageningen University as well as in Physics at Utrecht University. She obtained her PhD degree from Utrecht University in 1994, and was awarded twice a prestigious EU Marie-Curie Individual Fellowship to join the Physical and Theoretical Chemistry group at Oxford University and the H.H. Wills Physics Laboratory at Bristol University.

In 1999, she started her own research line at Utrecht University on obtaining a fundamental understanding on how colloidal building blocks self-assemble and how the self-assembly process can be manipulated by external fields such as gravity, templates, air-liquid or liquid-liquid interfaces, and electric fields. Her group employs Monte Carlo, (event driven) Molecular and Brownian Dynamics simulations, Stochastic Rotational Dynamics simulations to include hydrodynamics, Umbrella and Forward flux sampling, free-energy calculations based on thermodynamic integration methods, and simulated annealing techniques, and more recently machine learning techniques, to determine the (non)-equilibrium phase behavior of colloids, nanoparticles, and liquid crystals.

She is recipient of the Minerva Prize (2000), a high-potential grant (2004), a prestigious NWO VICI and Aspasia grant (2006), and an ERC advanced grant (2020), and is elected as a member of the Royal Netherlands Academy of Arts and Sciences (KNAW). She is (vice) director of the Debye Institute for Nanomaterials Science, (consulting) editor of Reviews of Modern Physics, Physical Review X, and Molecular Physics, and has organised several international conferences and workshops.

Authors
Marjolein Dijkstra a
Affiliations
a, Debye Institute for Nanomaterials Science, NL
Abstract

In 1960, Feynman challenged us to think “from the bottom up” and to create new functional materials by directing and manipulating the arrangements of individual atoms ourselves. With recent advances in the colloidal nanoparticles synthesis and the bottom-up fabrication of nanostructured materials using colloidal self-assembly, we are tantalizingly close to realizing this dream. In this talk, I will show using computer simulations how one can use hierarchical self-assembly to structure matter over multiple length scales, which enables an unprecedented control over the properties and functionalities of these nanomaterials. For instance, combining two types of particles, e.g., metal particles and silica particles, in a binary crystal gives unprecedented control for the creation of novel catalysts systems, plasmonics, etc. In addition, the fabrication of larger supraparticles [1-3] of these nanostructured materials using the self-assembly in the spherical confinement of emulsion droplets allows for a subsequent self-assembly step which provides opportunities for new functionalities like control over the porosity, plasmonic, and photonic properties.

 

 

[1]
[2]
[3] D. Wang, T. Dasgupta, E.B. van der Wee, D. Zanaga, T. Altantzis, Y. Wu, G.M. Coli, C.B. Murray, S. Bals, M. Dijkstra and A. van Blaaderen, Nature Physics 17, 128–134 (2021).

11:25 - 11:45
1.1-I3
Cortes, Emiliano
Ludwig- Maximilians-Universität München (LMU)
Hybrid Platforms for Plasmonic Catalysis
Cortes, Emiliano
Ludwig- Maximilians-Universität München (LMU), DE

Emiliano holds a W2 tenure-track professorship at the Physics Department in LMU Munich and is the academic lead of the Plasmonic Chemistry Group. He is also a visiting researcher at the Chemistry Department, University College London, UK, and at the Physics Department, Imperial College London, UK.

His research interests lie at the interface between chemistry and physics, and focus on the development of novel nanomaterials and techniques, specifically for applications in energy conversion.

Emiliano studied chemistry at the National University of La Plata in Argentina. He was one of the founders of Nanodetection, a start-up company based on plasmonic sensing. He was also a Marie-Skłodowska-Curie research fellow at Imperial College London. In 2018, he was awarded with the ERC Starting Grant from the European Commission for his project CATALIGHT.

He is currently a Principal Investigator (PI) of two German excellence research clusters, Nanoinitiative Munich (NIM) and e-conversion; member of the Munich-based Centre for NanoScience (CeNS) and the Bavarian program Solar Technologies go Hybrid (SolTech). Since March 2019, Emiliano is also a member of the Young Academy of Europe (YAE) and he is currently co-editing the first book in Plasmonic Catalysis (Wiley, Apr. 2021).

Authors
Emiliano Cortes a
Affiliations
a, University of Munich (LMU), Nanoinstitute Munich, Königinstraße 10, (80539) Munich, Germany
Abstract

Photons, electrons, and phonons can be channeled and manipulated to create plasmonic and photonic chemical hotspots. Independent of the exact mechanism operating at plasmonic or photonic interfaces, great contributions to the field photocatalysis have been made in recent years. Plasmons for example, have opened access to enhance and control chemical reactivity with CW illumination in the visible range, a fundamental requisite for sunlight photocatalysis. Further understanding and control of these processes could hopefully impact potential industrial applications of photocatalysis, which so far have remained elusive

Optical modes engineering in metallic and dielectric nanoparticles could open new paths for assisting chemical transformations using sunlight. In recent years, we have investigated these phenomena at the single nanoparticle level in order to unravel the mechanisms inducing catalytic transformations at these illuminated interfaces. Here I will show how gaining a nanoscopic insight of these processes could aid in the rational design of novel plasmonic and photonic photocatalysts and platforms [1-10].

11:45 - 12:05
Discussion
UPDOWN 1.1
Chair: Kaifeng Wu
10:45 - 11:05
1.1-I1
Yanai, Nobuhiro
Kyushu University
Solving Challenging Problems in Visible-to-UV and NIR-to-Visible Photon Upconversion by Developing New Dyes
Yanai, Nobuhiro
Kyushu University, JP
Authors
Nobuhiro Yanai a
Affiliations
a, Kyushu University, JP
Abstract

Photon upconversion from visible to ultraviolet (UV) light was inefficient, and photon upconversion from near-infrared (NIR) to visible light was difficult. We show how the development of new dyes has overcome these application-relevant issues.

The discovery of a new excellent UV emitter, TIPS-naphthalene, has enabled the highest visible-to-UV upconversion efficiency of 20.5%. In addition, the threshold excitation intensity is lower than the solar irradiance, and UV light can be generated even from sunlight or desk LED lights.

NIR-to-visible upconversion has been difficult due to the energy loss caused by the intersystem crossing (ISC) of triplet sensitizers, but by using Os complexes that show S-T absorption, which essentially contains no energy loss of ISC, it has become possible to convert from NIR to yellow, blue, and even violet light with good efficiencies.

11:05 - 11:25
1.1-I2
Zhao, Jianzhang
Dalian University of Technology
Charge Recombination Induced Intersystem Corssing in Compact Electron Donor-Acceptor Dyads and its Application in Triplet-Triplet Annihilation Upconversion
Zhao, Jianzhang
Dalian University of Technology, CN

Jianzhang Zhao earned a Ph.D. degree from the Department of Chemistry at Jilin University in 2000. After postdoctoral
research at the Pohang University of Science and Technology (South Korea), the Max Planck Research Unit for Enzymology of Protein Folding (Halle, Germany) and the University of Bath (UK), he took up the current position of Professor at the Dalian University of Technology in 2005. His research interests are studying the charge separation, intersystem crossing and electron spin dynamics of organic materials with femtosecond/nanosecond transient absorption spectroscopic methods, and time-resolved electron paramagnetic resonance (TREPR) spectroscopy.

Authors
Xue Zhang a, Xiao Xiao a, Xiaoyu Zhao a, Jianzhang Zhao a
Affiliations
a, Dalian University of Technology, Dalian, 116024,, CN
Abstract

Triplet-triplet-annihilation (TTA) upconversion has attracted much attention due to the easily tunable molecular systems, strong absorption of photoexcitation, high upconversion quantum yields.[1] Triplet photosensitizers and triplet acceptors are used in TTA upconversion. Triplet photosensitizers are responsible for excitation light harvesting, then intersystem crossing, and triplet energy donor. Triplet acceptor is responsible for TTA and emission of the upconverted fluorescence. TTA upconversion has been used in photovoltaics, photocatalysis and luminescence bioimaging. One of the important areas in TTA upconversion is to develop new and efficient triplet photosensitizers. Concerning this aspect, it is still a major challenge to design heavy atom-free organic triplet photosensitizers. Recently, triplet photosensitizers based on spin-orbit charge transfer (SOCT) ISC was reported.[2,3] Herein we used Bodipy as visible light-harvesting moiety as well as electron acceptor, and anthracene and phenothiazine as electron donor, to prepare compact electron donor/acceptor dyads.[4,5] Efficient ISC was observed for the dyads, and one of the advantages of the new triplet photosensitizers is the long triplet state lifetime, due to the elimination of the heavy atom effect in the normal triplet photosensitizers. We aslo found that by tunning the electronic coupling magnitude between the electron donor and acceptor, charge transfer absorption band is resulted, which is useful to attain large anti-Stokes shift in TTA upconversion.[6] The dyads were used efficient triplet photosensitizers for TTA upconversion. Upconversion quantum yields up to 10% was observed.

11:25 - 11:45
1.1-I3
Guldi, Dirk
Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Molecular Up-Conversion
Guldi, Dirk
Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), DE

Dirk M. Guldi completed both his undergraduate studies (1988) and PhD (1990) at the University of Cologne (Germany). Following postdoctoral appointments at the National Institute of Standards and Technology (USA), the Hahn-Meitner Institute Berlin (1992), and Syracuse University, he joined the faculty of the Notre Dame Radiation Laboratory in 1995. He was promoted a year later from assistant to associate professional specialist, and remained affiliated to Notre Dame until 2004. Since 2004, he is Full Professor in the Department of Chemistry and Pharmacy at the Friedrich-Alexander University in Erlangen. Since 2018, Dirk M. Guldi is Co-Editor in Chief of Nanoscale and Nanoscale Horizons and he has been named among the world’s Highly Cited Researchers by Thomson Reuters.

The Guldi group and its network belong to the cutting edge of worldwide research in solar-energy conversion with expertise not only in advanced photon- and charge-management, but also in the synthesis of tailored materials and molecular modeling. Impressive documentations of their accomplishments are more than 700 peer-reviewed publications, nearly 40,000 citations, and an h-index of 100. At the heart is always a multifaceted and interdisciplinary research program, where his group designs, conceptually devises, synthesizes, tests, and characterizes novel nanometer scale materials with the objective of using them in solar energy conversion schemes. A broad range of spectroscopic (i.e. time-resolved and steady-state measurements with spectrophotometric detection covering a time range from femtoseconds to minutes) and microscopic techniques (i.e. scanning probe microscopy, electron microscopy) are routinely employed to address aspects that correspond to the optimization and fine-tuning of dynamics and/or efficiencies of charge separation, charge transport, charge shift, and charge recombination processes.

Authors
Dirk Guldi a
Affiliations
a, Friedrich-Alexander-Universität Erlangen-Nürnberg, Chair of Chemical Reaction Engineering
Abstract

The Shockley-Queisser limit places an upper bound on solar conversion efficiency for a single p-n junction solar cell at slightly more than 30%. To surpass this limit, multi-exciton generation is being explored in inorganic semiconductors, while singlet fission (SF) is being investigated in arrays of conjugated organic molecules. In an optimal SF process, the lowest singlet excited state of one molecule (S1) that is positioned next to a second molecule in its ground state (S0) is down-converted into two triplet excited states (T1) each residing on one of the two adjacent molecules. The two triplet states initially form a correlated pair state 1(T1T1), which then evolves into two separated triplet states (T1 + T1). As such, the energetic requirement for SF is E(S1) ≥ 2 ´ E(T1).

We have set our focus in recent years on intramolecular SF in molecular materials and their studies in solution rather than on intermolecular SF investigations in crystalline films. Implicit in intramolecular SF is a resonant, direct excitation of the SF material. In pentacene dimers linked by a myriad of molecular spacers, SF takes place with quantum yields of up to 200%. In addition, all key intermediates in the SF process, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons, have been identified. This approach is, however, limited to the part of the solar spectrum, where, for example, the pentacene dimers feature a significant absorption cross-section. To employ the remaining part of the solar spectrum necessitates non-resonant, indirect excitation of the SF materials via either up- or down-conversion. For example, the up-conversion approach is realized with singlet excited states in pentacene dimers, which are accessed by two-photon absorptions (TPA). TPA is then followed in the second step of the sequence by an intramolecular SF – similar to what is seen upon resonant, direct excitation. Quite different is the down-conversion approach, which is based on an intramolecular Förster resonance energy transfer (FRET) and thereby the (photo)activation of the SF material. FRET requires the use of a complementary absorbing chromophore and enables funneling its excited state energy unidirectionally to the SF performing pentacene dimer. Again, SF completes the reaction sequence.

11:45 - 12:05
Discussion
ORGELE 1.2
Chair: Bluebell Drummond
12:05 - 12:15
1.2-T1
Cho, Hwan-Hee
University of Cambridge
Towards more efficient and stable organic radical-based light-emitting diodes with exciplex host and near-infrared emission
Cho, Hwan-Hee
University of Cambridge, GB
Authors
Hwan-Hee Cho a, Shun Kimura b, Neil C. Greenham a, Richard H. Friend a, Tetsuro Kusamoto c, Emrys W. Evans d
Affiliations
a, Optoelectronics Group, Cavendish Laboratory, University of Cambridge, UK., J.J. Thomson Avenue, Cambridge, GB
b, Department of Chemistry, School of Science, University of tokyo
c, Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science
d, Swansea University, Department of Chemistry, Singleton Park, Swansea SA2 8PP, UK, Swansea, GB
Abstract

Despite extensive research on near-infrared organic light-emitting diodes, the external quantum efficiency (EQE) of these devices are far lower than devices with visible light emission: typically under 5% EQE for 800 nm and longer wavelengths. Recently, doublet fluorescent emission from organic radicals has emerged as a new route to more efficient light-emitting devices than those using established non-radical organic emitters. Charge recombination in radical devices results in doublet excitons with nanosecond emission and avoids the efficiency limit usually associated with singlets and triplets. While our recent report demonstrated almost 100% internal quantum efficiency from the radical emitters, device stability has not yet been thoroughly studied. In general, direct charge trapping to the radical is considered as the primary emission process due to the host’s much wider energy gap than the dopant. However, this trap-assisted emission detrimentally affects efficiency characteristics and operational lifetime due to the narrow emission zone and poor charge balance in the emitting layer. For more efficient and stable near-infrared devices, we have designed a novel near-infrared radical emitter based on (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl (PyBTM) radical with an 820 nm emission peak. This design leads to the radical having strong absorbance between 400 and 550 nm, enabling more efficient energy transfer from the host in electroluminescence. We used mixed-host exciplex systems as an exciton donor to the radical for improving the efficiency roll-off and operational lifetime. As a result, not only the maximum external efficiency of 10.9% was obtained, but also more than two orders of magnitude increase in device stability were attained when mixed hosts were exploited. This shows the disruptive potential of efficient and stable near-infrared electroluminescence based on doublet emission.

12:15 - 12:25
1.2-T2
de Sousa Rodríguez, Jesús Alejandro
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
Stable triphenylmethyl organic radical based SAMs for multiple electronic applications.
de Sousa Rodríguez, Jesús Alejandro
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain, ES
Authors
Jesús Alejandro de Sousa Rodríguez a, d, Francesc Bejarano a, Diego Gutiérrez a, Maria Benedetta Casu c, Jaume Veciana a, Marta Mas-Torrent a, Bruno Fabre b, Concepció Rovira a, Núria Crivillers a
Affiliations
a, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Networking Research Center on Bioengineering Biomaterials and Nanomedicine (CIBER-BBN), Campus de la UAB, 08193 Bellaterra, Spain
b, Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)-UMR 6226, F-35000 Rennes, France
c, Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
d, Laboratorio de Electroquímica, Departamento de Química, Facultad de Ciencias, Universidad de los Andes, 5101 Mérida, Venezuela
Abstract

Organic electronic devices are envisaged as the future of miniaturization technology since organic molecules could act as switches, capacitors, wires and rectifiers, among others.[1] Organic free radicals based materials have awakened much interest because they are electro- and magnetically active, and have been applied in different fields such as batteries, bio-imaging, spintronics,  as conductors, and switchable surfaces among others.[2] In this work, intending to expand the functionalities of these radicals, we exploited the versatility of alkyne chemistry to prepare functional surfaces. By one hand, we have functionalized Si–H surfaces achieving a light-triggered switch and on the other hand, we have explored the click chemistry on Au, which to the best of our knowledge is the first time that is used to chemically modify triphenylmethyl radicals. [3]

As a proof of concept, we have employed click chemistry to link an organic perchlorinated triphenylmethyl radical (PTM) and a donor molecule such as the ferrocene (Fc) through the formation of a triazole ring. The functionalization was carried out in solution and on surface. Electrochemical techniques have been used for the study of the PTM-Fc functionalized surfaces as a capacitive switching, getting stabilities over 40 cycles and well-differentiated three capacitive states.

Furthermore, the charge-transport through Si-alkyl-SAMs and the donor-acceptor Au-alkyl-SAMs has been studied using an eutectic alloy of gallium and indium (EGaIn) to top contact the modified substrates. On Au-alkyl-SAMs, different electrical response between the free radical and the donor-acceptor molecule-based SAMs was obtained. Interestingly, Si-alkyl-SAMs showed a diode behaviour. Under irradiation, from the interface current-voltage characteristics an open-circuit voltage (Voc) along with a short circuit current (Isc) could be calculated. This suggests that the p-Si/alkylPTM.// /EGaIn diode could behave as a photovoltaic device with Voc = -139mV and Jsc = 38 uA/cm2 values under 3.2mW/cm2 illumination intensity.

In summary, the organic radical modified with de alkyne group employed for this work is presented as a versatile platform to react not only with different surfaces but also with other functional moieties through click chemistry to expand their multifunctionality and thus their possible applications.

12:25 - 12:35
1.2-T3
Cookson, Aaron
Swansea University, Department of Chemistry
Small Molecule Memristors for Neuromorphic Computing
Cookson, Aaron
Swansea University, Department of Chemistry, GB
Authors
Aaron Cookson a, James W. Ryan a
Affiliations
a, Department of Chemistry, Swansea University, Singleton Park, Swansea SA2 8PP, UK
Abstract

Neuromorphic computation is a promising way to overcome the limits of the von Neumann chip architecture in modern computing. Memristors can play a key role in the realization of neuromorphic devices due to their inherent memory storage and ability to dynamically alter physical properties such as resistance in response to an incoming stimulus.[1] Organic memristive devices have the potential to generate new paradigms in the memristor device field due to the inherent ability to tune the electronic properties of organic molecules for greater electrical or memory/volatility performance, which is currently a bottleneck for solid-state transition metal oxide (TMO) memristors. [2],[3]  In this talk, I highlight a new approach to fabricate high performance memristive devices based on small molecules. First, I will highlight our recent demonstration of an organic memristor based on 2,4-bis[4-(diethylamino)-2-hydroxyphenyl]squaraine (SQ) nanowires (NW) and then proceed to discuss some very recent developments in our lab. [4]

 

In our SQ study, devices were fabricated using a facile method involving self-assembly of SQ NWs on an interdigitated electrode substrate. These prototype devices demonstrate the hallmarks of memristor operation such as current hysteresis loops and dynamic conductivity in response to multiple voltage sweeps. The volatility of the conductivity states written to the device is also shown to have long memory retention without voltage bias, demonstrating non-volatility. These results are on par with benchmark transition metal oxide devices (TMO). Initial studies into the working mechanism of these devices have shown that they do not behave like established TMO memristors, nor any reported organic memristors, and suggest that the unique proton chemistry of this squaraine derivative is what gives rise to its memristance.

 

These results demonstrate a straightforward and very promising approach to fabricate robust and low-cost memristive devices. The fabrication method offers an excellent platform for device prototyping and high-throughput screening of potential memristive materials. Furthermore, it highlights the potential of small molecule mixed ionic-electronic conductors in organic memristors and organic electrochemical devices in general. Indeed, there are certainly a number of exciting routes to take in order to fully explore, and exploit, the potential of squaraine and related small molecule mixed conductors in the fields of bioelectronics, organic electrochemical transistors, organic batteries and neuromorphic computing.

References

1 - Zidan, M. A.; Strachan, J. P.; Lu, W. D., The future of electronics based on memristive systems, Nature Electron., 2018, 1 , 22−29

2 - van de Burgt, Y.; Melianas, A.; Keene, S. T.; Malliaras, G.; Salleo, A, Organic electronics for neuromorphic computing, Nature Electron., 2018, 1 (7), 386−397

3 - Sangwan, V. K.; Hersam, M. C., Neuromorphic nanoelectronic materials. Nat. Nanotechnol., 2020, 15 (7), 517−528

4 - O’Kelly, C. J., Nakayama, T. & Ryan, J. W., Organic Memristive Devices Based on Squaraine Nanowires. ACS Appl. Electron. Mater., 2020, 2, 3088-3092

12:35 - 12:45
Abstract not programmed
12:45 - 13:15
Discussion
PEREMER 1.2
Chair: Paulina Plochocka
12:05 - 12:15
Abstract not programmed
12:15 - 12:25
1.2-T1
Grozema, Ferdinand
Delft University of Technology, The Netherlands
Tuning the properties of 2D hybrid perovskites by engineering the organic component
Grozema, Ferdinand
Delft University of Technology, The Netherlands, NL
Authors
Ferdinand Grozema a
Affiliations
a, Delft University of Technology, The Netherlands, Julianalaan, 136, Delft, NL
Abstract

Two-dimensional hybrid perovskites are promising materials for a wide range of opto-electronic applications. Their properties markedly differ from those of their three-dimensional analogues, but they also offer additional routes to engineer their properties by introducing specific functionality in the organic component. Until now, most of the large organic cations used in 2D or quasi-2D perovskite materials only act as a spacer, defining the dimensionality of the system. Their HOMO-LUMO gap is generally very large and the electronic properties of the resulting materials are fully determined by the properties of the inorganic layers.

In this work we aim to engineer the properties of the 2D perovskite materials by introducing specific organic moieties that have additional functionality. In general, there are two ways in which the organic molecules affect the properties of the perovskite; indirect and direct. The indirect effect is due to the way the layer of organic molecules influences the structure and dynamics of the inorganic layer, which also has an immediate effect on the electronic structure. For example, by tuning the interactions between the organic molecules the structural stability, humidity resistance and (chiral) distortions can be affected. Our molecular dynamics simulations show that both the nature and size of the aromatic unit and the flexibility of the linker are important.

The electronic properties can also be directly affected by introducing organic molecules that directly take part in the electronic states. An example of such functionality that we explored is the introduction of electron donors or acceptors resulting in enhanced charge separation. By density functional theory calculations we show that it is possible to introduce conjugated molecules that have a significant effect on the electronic structure. Based on these calculations we have synthesized new materials and have characterized them using ultrafast spectroscopy and microwave conductivity measurement.

Both of the approaches discussed in this contribution can be used to tunes and introduce new properties in 2D perovskites by exploiting the synergy between the inorganic and organic components.

12:25 - 12:35
1.2-T2
Saba, Michele
Università di Cagliari
Polaron plasma in 2D hybrid perovskites
Saba, Michele
Università di Cagliari
Authors
Michele Saba a
Affiliations
a, Università di Cagliari - Dipartimento di Fisica, Cittadella Universitaria, Monserrato, 0, IT
Abstract

Angelica Simbula, Riccardo Pau, Qingqian Wang, Fang Liu, Stefano Lai, Daniela Marongiu, Francesco Quochi, Michele Saba*, Andrea Mura, and Giovanni Bongiovanni

Dipartimento di Fisica, Università di Cagliari, I-09042 Monserrato, Italy

E-mail: saba@unica.it

Layered 2D perovskites have contributed to rapid advances in perovskite photovoltaics, with stability and duration improving thanks to variations in materials composition. A major reason for the success of perovskite photovoltaics is the presence of free carriers as majority optical excitations in 3D materials at room temperature. On the other hand, the current understanding is that in 2D perovskites or at cryogenic temperatures insulating bound excitons form, which need to be split in solar cells and are not beneficial to photoconversion. Here we apply a tandem spectroscopy technique that combines ultrafast photoluminescence and differential transmission to demonstrate a plasma of unbound charge carriers in chemical equilibrium with a minority phase of light-emitting excitons, even in 2D perovskites and at cryogenic temperatures. We validate the technique with 3D perovskites and investigate 2D compounds basded on both Pb and Sn as metal cation. The underlying photophysics is interpreted as formation of large polarons, charge carriers coupled to lattice deformations, in place of excitons. A conductive polaron plasma foresees novel mechanisms for LEDs and lasers, as well as a prominent role for 2D perovskites in photovoltaics.

12:35 - 12:45
1.2-T3
Gélvez-Rueda, María
Delft University of Technology, The Netherlands
Inducing Charge Separation in Solid-State Two-Dimensional Hybrid Perovskites
Gélvez-Rueda, María
Delft University of Technology, The Netherlands, NL
Authors
María Gélvez-Rueda a, Wouter Van Gompel b, Roald Herckens b, Laurence Lutsen b, Dirk Vanderzande b, Ferdinand Grozema a
Affiliations
a, Department of Chemical Engineering, Delft University of Technology (TU Delft), The Netherlands, NL
b, U Hasselt – Hasselt University, Institute for Materials Research (IMO-IMOMEC), BE, Agoralaan – Building D, Diepenbeek, BE
Abstract

Two-dimensional hybrid perovskites are promising materials for a wide range of opto-electronic applications such as solar cells, light-emitting diodes, nano-lasers and as photocatalysts. Compared to their 3D counterpart they exhibit higher stability and broader chemical versatility. An established view in the organic-inorganic perovskites field is that the optoelectronic properties are mostly determined by the inorganic component, as the valence and conduction bands are formed by the electronic orbitals of the inorganic elements. However, progressively is shown that the optoelectronic properties of 2D hybrid perovskites can be strongly affected by the nature of the organic cation either indirectly by structural strain or directly by contributing to the electronic states. In principle, via the organic cation a wide range of functionalities is accessible, e.g. charge transfer, chirality, photon management.

In 2D perovskites, the generation and transport of the electronic charges (electrons and holes) are limited to the inorganic octahedral layer where they strongly interact due to the strong dimensional and dielectric confinement (~350 meV). This results in the formation of strongly bound charge pairs (excitons) at room temperature, which is desirable for light-emitting applications, but not for solar cells and photo-catalyzers were charge separation is required. To improve charge separation, we introduced functional organic electron-donor moieties, pyrene-alkylammonium (pyrene-Cn), and full charge-transfer complexes of these donor molecules with tetracyanoquinodimethane (TCNQ),  and tetracyanobezene (TCNB) commonly used in solid state in the organic electronics field.

We have studied the photophysical properties of these compounds using laser-induced time-resolved microwave conductivity (TRMC) and femtosecond transient absorption (fs-TA) measurements. By microwave conductivity, we show that both the positive and negative charges in (pyrene-C4)2PbI4 are still confined to the inorganic layers (weak photoconductivity signal and fast decay kinetics). In contrast, the photoconductivity of (pyrene-C4:TCNQ)2PbI4 exhibits a long-lived signal component (∼1–4 μs) that we attribute to charge-separated holes transferred from the (pyrene-C4:TCNQ) CT complex into the inorganic octahedral layers, while the electrons stay localized in the TCNQ molecules. This was confirmed by the transient absorption (TA) measurements by direct photoexcitation of the high-energy CT state at 575 nm. While the efficiency of charge separation is relatively low, this shows for the first time that inclusion of charge-transfer complexes between the inorganic layers in 2D perovskites can result in charge transfer and long-lived free carrier conduction (1–4 μs) in solid-state 2D hybrid perovskites. The time scale is in the relevant range for application in optoelectronic devices.

12:45 - 13:15
Discussion
PERPOV 1.2
Chair not set
12:05 - 12:15
1.2-T1
Feldmann, Sascha
Cavendish Laboratory, University of Cambridge - UK
Tailored local bandgap modulation as a strategy to maximise the performance of mixed-halide perovskites
Feldmann, Sascha
Cavendish Laboratory, University of Cambridge - UK, GB

Sascha is an EPSRC Doctoral Prize Fellow at the University of Cambridge.

His research aims to tailor the optoelectronic properties of novel materials through chemical modifications. He investigates how material changes like doping, dimensionality and chirality impact the electronic structure, and thus enable more efficient devices or entirely new functionalities.

Before, he completed his PhD in Physics with Dr Felix Deschler and Prof Sir Richard Friend at the Cavendish Laboratory, where he investigated charge carrier dynamics in halide perovskite semiconductors for optoelectronic applications such as solar cells or lighting. He found that charge accumulation and localisation effects can be beneficial for device performance.

Authors
Sascha Feldmann a
Affiliations
a, Optoelectronics Group, University of Cambridge, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Abstract

Halide perovskites have emerged as high-performance semiconductors for efficient optoelectronic devices, not least because of their bandgap tunability using mixtures of different halide ions. This makes them particularly attractive as candidates for tandem solar cells or spectrally tailored lighting.

Recently, we demonstrated that spatially varying energetic disorder in the electronic states of such mixed-halide films causes local charge accumulation, creating photodoped regions, which unearths a strategy for efficient light emission at low charge-injection in solar cells and light-emitting diodes [1].

Now, we combine temperature-dependent photoluminescence microscopy with computational modelling to quantify the impact of local bandgap variations from disordered halide distributions on the global photoluminescence yield in mixed-halide perovskite films. We find that fabrication temperature, surface energy, and charge recombination constants are key for describing local bandgap variations and charge carrier funneling processes that control the photoluminescence quantum efficiency. We report that further luminescence efficiency gains are possible through tailored bandgap modulation, even for materials that have already demonstrated high luminescence yields. Our work provides a novel strategy and fabrication guidelines for further improvement of halide perovskite performance in light-emitting and photovoltaic applications.

[1] Feldmann et al., Nature Photonics 14, 123 (2020).

12:15 - 12:25
1.2-T2
Alsalloum, Abdullah
King Abdullah University of Science and Technology (KAUST) - Saudi Arabia
Single-Crystal Halide Perovskites for High Efficiency Photovoltaics
Alsalloum, Abdullah
King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, SA
Authors
Abdullah Alsalloum a, Osman Bakr a, Bekir Turedi a, Omar Mohammed a
Affiliations
a, King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal, SA
Abstract

Lead halide perovskite solar cells (PSCs) are considered the fastest growing photovoltaic technology to date, reaching outstanding power conversion efficiencies that are competing with state-of-the-art technologies. The best performing PSCs are based on polycrystalline films, where the presence of grain boundaries and ultra-fast crystallization limit the further development of their performance by increasing the bulk and surface defects. Compared with their polycrystalline counterparts, single crystals of lead halide perovskites have been shown to possess much lower trap-state densities, enhanced absorption and diffusion lengths exceeding 100𝜇m. In this talk, our recent developments in the area of single-crystal PSCs will be presented, with a particular focus on strategies to boost the efficiency toward the Shockley-Queisser limit for single-junction solar cells. 

12:25 - 12:35
1.2-T3
Malinauskas, Tadas
Kaunas University of Technology
Materials Forming Self-Assembling Monolayers - Effective Approach Towards Efficient Perovskite Solar Cells
Malinauskas, Tadas
Kaunas University of Technology, LT
Authors
Artiom Magomedov a, Ernestas Kasparavicius a, Amran Al-Ashouri b, Eike Köhnen b, Tadas Malinauskas a, Steve Albrecht b, Vytautas Getautis a
Affiliations
a, Kaunas University of Technology, Kaunas, 50254, Lithuania.
b, Helmholtz-Zentrum Berlin, Berlin, 12489, Germany
Abstract

Perovskite-based photovoltaics promise benefits of low cost, high efficiency and large versatility. However, combining all three factors into one solar cell is a difficult task. In particular, one of the bottlenecks towards large-scale production is the available choice of hole-selective contacts. The best standards in both polarities, n–i–p (Spiro-OMeTAD) and p–i–n (PTAA), are highly unsuitable for commercial production due to their high cost and limited processing versatility. Self-assembled monolayers as hole-selective contacts are a viable alternative as they are intrinsically scalable, simple to process, dopant-free and inexpensive. Self-assembly also offers the crucial advantage of conformally covering rough surfaces within a self-limiting, simple to control process, creating energetically well-aligned interface to the perovskite absorber with minimal non-radiative recombination. This approach enables highly efficient single-junction p–i–n perovskite solar cells and record-efficiency monolithic perovskite/CIGSe (24.2%) [1] as well as perovskite/silicon (PCE up to 29.15%) [2] tandem devices.

12:35 - 13:05
Discussion
SELFNC 1.2
Chair: Agustín Mihi
12:05 - 12:15
1.2-T1
Schulz, Florian
University of Hamburg
Synthesis and characterization of quasicrystalline plasmonic superlattices
Schulz, Florian
University of Hamburg, DE
Authors
Florian Schulz a, b, Felix Lehmkühler b, c, Niclas S. Mueller d, Ondřej Pavelka e, Fabian Westermeier c, Francesco Dallari c, Verena Markmann c, Yu Okamura d, Bruno G. M. Vieira d, f, Sabrina Juergensen d, Eduardo B. Barros f, Gerhard Grübel b, c, Stephanie Reich d, Holger Lange a, b
Affiliations
a, University of Hamburg, Institute of Physical Chemistry, Hamburg, DE
b, The Hamburg Center for Ultrafast Imaging (CUI), DE
c, DESY - Deutsches Elektronen-Synchrotron, Hamburg, Notkestraße, 85, Hamburg, DE
d, Department of Physics, Freie Universität Berlin
e, Charles University in Prague
f, Universidade Federal do Ceará, Departamento de Engenharia Metalúrgica e de Materiais, Universidade Federal do Ceará, Campus do Pici Bloco 714, Fortaleza, CE 60455-760, BR
Abstract

Superlattices of gold nanoparticles (AuNP) with diameters > 20 nm exhibit interesting optical properties. The periodic arrangement of the AuNP within the superlattices leads to new well-defined collective plasmon-polariton modes and with tailored geometries even deep strong light-matter coupling at room temperature is possible.[1][2] To observe and study these phenomena a precise control of superlattice geometry is crucial. The synthesis of such quasicrystalline superlattices with large domain sizes will be explained and discussed. The superlattices with a well‐defined layered structure are studied with transmission electron microscopy, small‐angle X‐ray scattering and X‐ray cross‐correlation analysis (TEM‐SAXS‐XCCA).[3] Their plasmonic properties are characterized by optical microscopy and spectroscopy.

12:15 - 12:25
1.2-T2
Goerlitzer, Eric
Institute of Particle Technology
Chiral Surface Lattice Resonances via Self-Assembly and Colloidal Lithography
Goerlitzer, Eric
Institute of Particle Technology, DE
Authors
Eric Goerlitzer a, Reza Mohammadi a, Sergey Nechayev b, Kirsten Volk c, Marcel Rey a, Peter Banzer b, d, Matthias Karg c, Nicolas Vogel a
Affiliations
a, Institute of Particle Technology, Friedrich‐Alexander University Erlangen‐Nürnberg
b, Max Planck Institute for the Science of Light and Institute of Optics, Information and Photonics, Friedrich‐Alexander University Erlangen‐Nürnberg
c, Institut für Physikalische Chemie I: Kolloide und Nanooptik, Heinrich‐Heine‐Universität Düsseldorf
d, Institute of Physics, University of Graz
Abstract

The collective excitation of a metallic nanoparticles by coupling diffractive to localised plasmonic resonances leads to narrow and strong surface lattice resonances. Tilting a planar metasurface comprising split-ring resonators leads to extrinsic chirality, which allows the lattice modes to selectively transmit circularly polarized light with opposing handedness. Here we propose to excite chiral lattice resonances under normal illumination in arrays of plasmonic crescents with intrinsic chirality. We apply self-assembly of masking soft core-shell particles and modified on-edge colloidal lithography to produce arrays of planar and 3-dimensional arrays over large areas (< cm²). The individual chiral crescents can be considered a chiral metamolecule and show strong circular dichroism at their localised plasmon resonances caused by overlapping electric and magnetic dipoles. Once brought into a suitable lattice the introduced 3-dimenionsal chiral character leads to the formation of chiral lattice modes, i.e. surface lattice resonances that show circular dichroism.

 

12:25 - 12:35
1.2-T3
Jia, Haiyan
ecole polytechnique federale de lausanne
In-situ self-assembly of injectable photovoltaic microspheres as potential retinal protheses
Jia, Haiyan
ecole polytechnique federale de lausanne, CH
Authors
Haiyan Jia a, Mahmut Selman Sakar a
Affiliations
a, Institute of Mechanical Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Abstract

Biomimetic retinas with wide field of view and high resolution are on demand in neuroprosthetics and robot vision. Conventional retinal prostheses are manufactured outside the application area and implanted as a complete device using invasive surgery. Here, a bioinspired strategy based on in situ self-assembly of functional photovoltaic microspheres (PVMs) is presented. The geometry and multilayered architecture of the PVMs along with the tunability of their physical properties such as size and stiffness facilitate the biomedical self-assembly process. The photoelectricity transduced by PVMs upon visible light illumination reaches the intensity levels that could effectively activate the retinal ganglion cell layers. Spatial distribution and packing density of the PVMs within the collective are modulated through concentration, liquid discharge speed and number of self-assembly steps. Subsequent injection of a photocurable and transparent polymer reinforces tissue integration and stabilize the colloidal assembly. Above all, this methodology introduces unique features such as i) minimally invasive implantation, ii) personalized visual field and acuity, and iii) adaptability to retina topography.

 

12:35 - 12:45
1.2-T4
Nagaoka, Yasutaka
Brown University
Bulk materials with tailored nanoscale grain-boundary conditions created from nanocrystals
Nagaoka, Yasutaka
Brown University, US
Authors
Yasutaka Nagaoka a, Ou Chen a
Affiliations
a, Brown University, Hope Street, 184, Providence, US
Abstract

Grain-boundary engineering is essential to unleash the potential of bulk materials in their mechanical, electrical, and thermal-transport properties. Especially, nanoscale grain-boundary conditions most critically determine materials’ properties, which has been investigated both theoretically and in experiments. However, it is difficult to achieve precise nanoscale grain boundary engineering with currently available methods in metallurgy because these methods rely almost exclusively on top-down approaches.  Herein, we show a new bottom-up method, the nanocrystal coining method, that can produce tailored grain-boundary conditions with nano-scale precision. The nanocrystal coining method uses chemically-synthesized colloidal metal nanocrystals as the starting materials, and employs surface treatment and a pressure-sintering process. The resulting bulk materials  (which we call ’’nanocrystal coins’’) possess a centimeter-scale in size, freestanding nature, and a metal-like appearance and conductivity while inheriting the crystal domains of the original nanocrystal building blocks. Nanoindentation measurements confirmed the superior mechanical hardness of the nanocrystal coins due to the Hall-Petch effect. Furthermore, the first example of a single-component bulk metallic glass was produced using the nanocrystal coining method from amorphous palladium nanoparticles. Our nanocrystal coining method can produce materials with as-tailored grain-boundary conditions with at least one-nanometer precision and crystal domain shape, from a wide range of metal components. We believe that our methods can produce ultimately optimized materials whose functionality crucially depends on the domain configuration at nanoscales, such as superhard materials, thermoelectric generators, and functional electrodes.

12:45 - 13:15
Discussion
UPDOWN 1.2
Chair: Kaifeng Wu
12:05 - 12:15
1.2-T1
Bossanyi, David
Department of Physics and Astronomy, University of Sheffield, UK
Triplet-Triplet Annihilation in Rubrene Nanoparticles: the Roles of Singlet Fission, Singlet Energy Collection and Spin Statistics
Bossanyi, David
Department of Physics and Astronomy, University of Sheffield, UK, GB
Authors
David Bossanyi a, Yoichi Sasaki b, Nobuhiro Yanai b, Jenny Clark a
Affiliations
a, Department of Physics and Astronomy, University of Sheffield, UK, Hounsfield Road, GB
b, Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
Abstract

The conversion of near infrared photons to visible light through triplet-triplet annihilation upconversion offers an enticing strategy for significantly boosting the efficiency of conventional solar cell technology. Rubrene is the acceptor molecule of choice for realising such upconversion, yet despite its ubiquitousness, several aspects of the underlying photophysical mechanisms remain unclear. In this study, we investigate the interplay of singlet fission, triplet fusion and singlet energy collection in recently developed rubrene-based nanoparticles by employing transient spectroscopy to probe the excited state dynamics from picoseconds to hundreds of microseconds. We clarify the role of the singlet energy collector tetraphenyldibenzoperiflanthene (DBP), in particular demonstrating that it does not suppress the formation of triplet-pair states via singlet fission in rubrene. We use our results to construct kinetic scheme for triplet-triplet annihilation in rubrene nanoparticles and use it to investigate the effects of exchange energy and molecular orientation within triplet-pair intermediates. We show that triplet-pairs formed through triplet-triplet annihilation may not be the pure spin states usually assumed, but instead have mixed character. These results raise the possibility that altering triplet-pair orientation through molecular engineering and morphological control may enable manipulation of the spin statistics of upconversion.

12:15 - 12:25
1.2-T2
Bharmoria, Pankaj
Chalmers University of Technology, Sweden
Photon Upconverting Bioplastics with High Efficiency and In-Air Durability
Bharmoria, Pankaj
Chalmers University of Technology, Sweden, SE

I am an “Experimental Biophotophysical Chemist,” working at the interface of photophysics, chemistry and biology to utilize the potential of biomacromolecule-surfactant systems as sustainable materials for applications ranging from renewable energy to bio photonics. I was born at Sandhole, Himachal Pradesh India. I graduated in Science and Post-graduated in Physical Chemistry from Himachal Pradesh University, Summer Hill Shimla, India.  I did my PhD in Biophysical Chemistry from CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar India, in 2015 with Dr. Arvind Kumar as Ph. D Supervisor. After Ph. D I started my research career abroad. First as ERC Post Doc Researcher at CICECO Aveiro University, Portugal with Prof. Mara G Freire in 2016 and with Prof. Joao A P Coutinho and Sonia Ventura in 2019. Later I won the prestigious JSPS Post Doc grant and worked with Prof. Nobuo Kimizuka and Prof. Nobuhiro Yanai at Kyushu University, Japan from 2016 to 2018. In 2019 I was awarded the presentigious Marie Curie Post Doc grant at Chalmers University of Technology Sweden with Prof. Kapser Moth-Poulsen. My recent research interests are focused on photon upconversion via triplet-triplet annihilation and sustainable solar concentration in biomaterials for biophotonic and photovoltaic applications. My past research is focused on preparation of surfactant membrane (micelles, vesicles) in water and ionic liquids, Biopolymer-surfactant chemistry, Microfabricatin of biopolymer-surfactant thin films, ionogels, hydrogels, ionic liquid-based biopolymers extraction, quantum dots synthesis using IL based colloids as templates and development of methods for fast protein fibrillation. 

Authors
Pankaj Bharmoria a, Shota Hisamitsu b, Yoichi Sasaki b, Tejwant Singh Kang c, Masa-aki Morikawa b, Biplab Joarder d, Kasper Moth-Poulsen a, Hakan Bildirir a, Anders Mårtensson a, Nobuhiro Yanai b, Nobuo Kimizuka b
Affiliations
a, Chalmers University of Technology, Sweden, Fysikgränd, 3, Gothenburg, SE
b, Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
c, Department of Chemistry, UGC-centre for Advance Studies – II, Guru Nanak Dev University, Amritsar, 143005, India
d, Functional Materials, Design, Discovery & Development (FMD3), Advanced Membrane & Porous Materials Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
Abstract

There is an urgent demand for substituting synthetic plastics to bioplastics for sustainable renewable energy production. Here we are presenting our simple one-step approach to create bioplastics with efficient and durable photon upconversion (UC) by encapsulating non-volatile chromophore solutions into collagen-based protein films. By just drying an aqueous solution of gelatin, surfactant, and UC chromophores (sensitizer and annihilator), liquid surfactant microdroplets containing the UC chromophores are spontaneously confined within the gelatin films. Thanks to the high fluidity of microdroplets and the good oxygen barrier ability of the collagen-based fiber matrices, a high absolute TTA-UC efficiency of 15.6% and low threshold excitation intensity of 14.0 mW cm-2 is obtained even in air. The TTA-UC efficiency was retained up to 8.2% after 2 years of storage in ambient conditions, hence displaying the significant durability desired for practical applications.

12:25 - 12:35
1.2-T3
VanOrman, Zachary
Florida State University
Sensitizer Material Dimensionality Effects on Triplet Fusion Upconversion
VanOrman, Zachary
Florida State University, US
Authors
Zachary VanOrman a, Lea Nienhaus a
Affiliations
a, Department of Chemistry and Biochemistry, Florida State University, Tallahassee, 32306 Florida, United States
Abstract

Photon upconversion via triplet fusion or triplet-triplet annihilation resulting in blue and ultraviolet photons could be useful for applications including photocatalysis. Semiconductor nanocrystals, such as CdSe quantum dots, have been previously utilized as triplet sensitizers in such schemes resulting in efficient upconversion. However, these works have only focused on 0D quantum dots, ignoring other material dimensionalities that exhibit unique properties endowed by differing morphologies. This talk focuses on two recent works dedicated to elucidating the effect that material dimensionality has on the triplet sensitization process. Specifically, CdSe nanoplatelets[1] and CdTe nanorods[2] have been paired with 9-anthracenecarboxylic acid and 9,10-diphenylanthracene, resulting in green-to-blue and red-to-blue upconversion, respectively. In both cases, the ternary UC system resulted in relatively efficient UC at fairly low fluences. Still, unique parasitic channels, such as nanoplatelet stacking and nanorod aggregation lower efficiencies. Further study of triplet sensitizers of differing dimensionalities could yield unique devices capable of efficient upconversion while endowed with the properties of the 1D/2D triplet sensitizer, allowing for new approaches to triplet fusion upconversion.

12:35 - 13:05
Discussion
13:05 - 14:00
PEROPV Break
13:05 - 14:00
UPDOWN Break
13:15 - 14:00
ORGELE Break
13:15 - 14:00
PEREMER Break
13:15 - 15:15
SELFNC Break
14:00 - 14:05
ORGELE Opening nanoGe
14:00 - 14:05
PEREMER Opening nanoGe
14:00 - 14:05
PEROPV Opening nanoGe
14:00 - 14:05
UPDOWN Opening nanoGe
ORGELE 1.3
Chair: Eleni Stavrinidou
14:05 - 14:15
1.3-T1
Gladisch, Johannes
Linköping University
Electrochemically controlled solid-gel transition induces unprecedented volume change in a conjugated polymer
Gladisch, Johannes
Linköping University, SE
Authors
Johannes Gladisch a, Sarbani Ghosh a, Maximilian Moser b, Vasileios Oikonomou a, Alexander Giovannitti c, Igor Zozoulenko a, Iain McCulloch b, d, Magnus Berggren a, Eleni Stavrinidou a
Affiliations
a, Linköping University, Bredgatan, 33, SE
b, University of Oxford, UK
c, Stanford University, Stanford, CA 94305, US
d, King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal, SA
Abstract

Controlled volume change is of interest for a wide range of applications, for instance mechanical actuators or drug delivery. Due to their wide range of customizability and properties, one group of materials that attracted particular attention for such applications are polymers. The molecular properties of polymer hydrogels for example enable very large volume changes but control over the volume change is limited. Then again, conjugated polymers can be straightforwardly triggered electrochemically and reversibly but exhibit limited volume changes.

We recently presented a thiophene based polymer with glycol side chains that features properties of both conjugated polymers and hydrogels upon electrochemical switching. p(g3T2) exhibits unprecedented volume changes of 300% in a reversible manner and more than 10 000% irreversibly when electrochemically addressed. p(g3T2) outperforms other conjugated polymers that have been typically used in electrochemical actuators such as Polypyrrole. The giant volume change is due to a reversible solid-gel transition, as verified from electrochemical quartz microbalance and molecular dynamic studies. We further investigate the effect of side chains length on the swelling extent and stability during cycling. Not least we explore possible applications of such materials.

14:15 - 14:25
1.3-T2
Siemons, Nicholas
Imperial College London
Multi-scale Modelling of Conjugated Polymers to Understand the Role of Side Chain Chemistry in Mixed Ionic- Electronic Conduction
Siemons, Nicholas
Imperial College London, GB
Authors
Nicholas Siemons a, Jarvist Frost a, Drew Pearce a, Jenny Nelson a
Affiliations
a, Department of Physics, Imperial College London, London SW7 2AZ, UK
Abstract

Control of mixed ionic-electronic conduction is essential for high performance organic electrochemical devices such as organic electrochemical transistors, ion sensors, supercapacitors and batteries. In many designs of organic mixed conductors, ethylene-glycol based side chains are used to enable uptake of water and ions into the bulk of a polymer film while the conjugated backbone conducts electronic charge. 3–5 However, engineering of side chains, for example by mixing ethylene-glycol with alkyl chains, modulates the electrochemical and mechanical properties of the films and can impact the device performance.1,2 Methods to predict the properties of organic mixed conductors as a function of side chain type would therefore be very useful for design of improved materials. In this work, we present a molecular dynamics force field to model polymers based on homo-3,3’-dialkoxybithiophene with both ethylene-glycol (gT2) and alkylated (aT2) side chains. The force field is validated by comparison of measured and simulated crystal structures for the gT2 and aT2 monomers and is then used to determine crystal structures for oligomers of g(T2) and a(T2). We further investigate the interactions of the crystal phase with both water and electrolyte. We find that the crystal structure adopted, and the interactions with water and ions, depend strongly on the side chain. We also study amorphous phases of copolymers of g(T2) and a(T2) units to elucidate the impact of mixed chains on polymer structure and interactions. It is found that addition of alkyl side chains appears to impact both the electronic properties and the degree of passive swelling of amorphous films.

14:25 - 14:35
1.3-T3
Dufil, Gwennaël
Linköping University, Sweden
Conjugated Thiophene Oligomers for In-Vivo Polymerized Self-Organized Conductors
Dufil, Gwennaël
Linköping University, Sweden, SE
Authors
Gwennaël Dufil a, Daniela Parker a, Daniele Mantione b, Emin Istif b, Eleni Pavlopoulou b, Eleni Stavrnidou a
Affiliations
a, Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-601 74 Norrköping, Sweden
b, Laboratoire de Chimie des Polymères Organiques (LCPO−UMR 5629), Université de Bordeaux, Bordeaux INP, CNRS, F-33607 Pessac, France
Abstract

One of the main challenges of organic bioelectronics is to reduce the biological response from the host when devices are implanted. We have previously shown that plants can be directly functionalized with organic electronic materials and demonstrated electrochemical devices integrated within the plants’ organs. The thiophene based conjugated oligomer, ETE-S, polymerized in-vivo in the vascular tissue of the plant. Recently, we have elucidated the mechanism that drives the polymerization of ETE-S in the plant. We found that the ETE-S polymerizes due to the activity of the peroxidase enzyme. This enzyme regulates H2O2 levels in the plant and modifies the physical properties of the plant’s cell wall. ETE-S, therefore, integrated within the cell wall structure. Furthermore, we synthesized three new trimers: the ETE-N, the EEE-N, and the EEE-S that also showed the ability to polymerize through the peroxidative catalytic reaction of plant peroxidases. We discovered that the molecular structure impacts the localization of the polymer and the interaction with the plant cells. Our work paves the way for rational design of materials that can self-organize in vivo for controlled electronic functionalization of living tissue also extended beyond plant systems.

14:35 - 14:45
1.3-T4
Paulsen, Bryan
Northwestern University
Operando Structure Determination of Organic Mixed Ionic-Electronic Conductors
Paulsen, Bryan
Northwestern University, US
Authors
Bryan Paulsen a, Ruiheng Wu b, Christopher Takacs c, Joseph Strzalka d, Qingteng Zhang d, Jonathan Rivnay a, e
Affiliations
a, Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
b, Department of Chemistry, Northwestern University, Evanston, IL, 60208, USA
c, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
d, X-Ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
e, Simpson Querrey Institute, Northwestern University, Chicago, Illinois 60611, USA
Abstract

Conjugated polymer based organic mixed ionic-electronic conductors (OMIECs) are an exciting class of materials for electrochromic, charge storage, biological sensor, neuromorphic, and electrochemical transistor applications, amongst others. In these electrolyte swollen applications the structure of OMIECs are not constant, rendering static ex situ characterization inadequate. Here, we report the grazing incidence x-ray scattering of the prototypical polythiophene/polyelectrolyte blend, PEDOT:PSS, and the glycolated polythiophene, p(g2T-TT), under operating conditions (i.e. exposed to electrolyte, at controlled electrochemical potential). This has required the development of new in situ/operando cells that overcome electrolyte absorption/scattering to preserve the scattered x-ray intensity from the OMIEC film. Steady-state and time-resolved measurements reveal the profound effect of electrolyte on crystallite lattice spacings and quantify the structural kinetics that accompany the electronic charging of and discharging, respectively. Operando measurements reveals that ex situ characterization can underestimate OMIEC crystallite lattice spacings by as much as 10 Å. Coupled with optical and X-ray spectroscopy, we correlate these results with doping composition, charge carrier dynamics, and charge trapping, which gives insight into electronic transport in these materials. In particular, this reveals how microstructural kinetics are dependent on the equilibrium of charge carrier sub-populations, while bulk conductivity is dependent on longer scale network formation. Finally, we discovered a surprising sensitivity of microstructure on side chain regio-chemistry revealing unexpected OMIEC design rules. On the whole this shows that operando characterization is critical to establishing structure-property relationships and elucidating design rules for next generation OMIECs. 

14:45 - 15:15
Discussion
PEREMER 1.3
Chair: Claudio Quarti
14:05 - 14:15
1.3-T1
Duim, Herman
University of Groningen, The Netherlands
High Quality 2D Perovskite Thin Films Obtained Through A Simple Blade-Coating Approach
Duim, Herman
University of Groningen, The Netherlands, NL
Authors
Herman Duim a, Sampson Adjokatse a, Simon Kahmann a, Gert ten Brink a, René de Kloe b, Bart Kooi a, Giuseppe Portale a, Maria Loi a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands, Nijenborgh 4, Groningen, NL
b, EDAX, AMETEK BV, The Netherlands
Abstract

Layered metal halide perovskites are attractive semiconductors for a range of different optoelectronic applications owing to their large structural versatility and rich photophysics. As is the case for the more conventional 3D perovskites, thin films of these materials can be deposited directly from solution, thereby holding the promise of procuring flexible and cost‐effective films through large‐scale fabrication techniques. However, such solution‐based deposition techniques often induce large degrees of heterogeneity due to poorly controlled crystallization. While much attention is focused on the optimization of thin film microstructure and its relation to device performance in the case of 3D perovskites, the microstructure of layered perovskite thin films remains markedly underexplored.

Herein, we present a detailed study on the optical properties and microstructure of the  archetypal 2D perovskite phenylethylammonium lead iodide ((PEA)2PbI4). Using a combination of polarized Raman spectroscopy, electron backscatter diffraction (EBSD), and grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) we demonstrate that thin films with large grains and strong texture are readily obtained through a simple and scalable blade-coating process. Moreover, we highlight the large impact that the stoichiometry of the precursor solution has on the crystallinity, morphology, and optical properties of the resulting thin films. We find that even for films cast from stoichiometric precursors, differences in local trap state densities occur on a subgranular level. A simple passivation step can greatly enhance the photoluminescence without significantly altering the film's morphology.

All in all, we illustrate the large potential for scalable fabrication of 2D perovskite films and underline some of the major hurdles to be overcome for the further development devices based on large area layered perovskite films.

14:15 - 14:25
1.3-T2
Kennard, Rhys
Materials Department, University of California, Santa Barbara
Using Octahedral Distortions to obtain Phase Purity in Two-Dimensional Perovskite Films
Kennard, Rhys
Materials Department, University of California, Santa Barbara, US
Authors
Rhys Kennard a, Clayton Dahlman a, Juil Chung a, Benjamin Cotts b, Lingling Mao a, Ryan DeCrescent c, Naveen Venkatesan a, Sepanta Assadi d, Alberto Salleo b, Jon Schuller d, Ram Seshadri a, e, Michael Chabinyc a
Affiliations
a, Materials Department, University of California, Santa Barbara, US
b, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
c, Department of Physics, University of California, Santa Barbara
d, Department of Electrical and Computer Engineering, University of California, Santa Barbara
e, Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106-9510, US
Abstract

Two-dimensional perovskites of the Ruddlesden-Popper (RP) family have emerged as attractive materials for energy conversion and light-emitting devices. RP-based and 2D/3D-based solar cells exhibit high power conversion efficiencies, as well as improved stability over their 3D counterparts. The Ruddlesden-Popper (A’)2(A)n1BnX3n+1 structure also promises light-emitting devices with tunable color. Conveniently, the RP optical gap can be changed by increasing the number n of metal-halide (B-X) octahedra that are contained between the large, organic A’ spacer cations. However, RP integration into light-emitting devices has proven challenging. Competing crystallization pathways lead to the formation of films with off-target n and 3D impurities. Carriers in RP films are thus funneled to the lowest-bandgap phase, such that the films exhibit emission that is closer to n = ∞ (3D material) than to powders of the targeted n. Few strategies have been proposed for obtaining phase-pure films, and have mostly been centered around changing the annealing procedures or substituting precursors.

 

Here, we show that Pb-X octahedral distortions can be used to obtain phase-pure films of large n. A-site and spacer cation sizes were targeted to obtain select patterns of distorted/undistorted octahedra. The resulting films exhibited the same structural and optical features as their target n powders. Notably, the n = 3 phase exhibited the same photoluminescence emission features as the n = 3 powder, and did not contain larger n or 3D emission. Spin-casting kinetics were found to control the relative populations of narrow-emitting vs. broad-emitting species. We also examined ease of formation and stability of films of various n using the selected A and A’ cations. Phase purity or lack thereof was attributed to the number and location of octahedral distortions. Since octahedral distortions are controlled by ion size, we estimate that careful ion size selection will further enable spin-casting of phase-pure RP films, as well as fabrication of novel 2D/3D heterostructure types.

14:25 - 14:35
Abstract not programmed
14:35 - 14:45
1.3-T3
Dong, Jingjin
Insights into the mechanism of crystallization of 3D and 2D perovskites from solution
Dong, Jingjin
Authors
Giuseppe Portale a, Jingjin Dong a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Abstract

Mixed organic-inorganic perovskites have attracted increasing attention for solar cell applications. Among the different possibilities, systems made by mixing 2D and 3D perovskite precursors yield production of devices with improved efficiency and stability. These systems are commonly referred to as Ruddlesden–Popper perovskites.

Knowledge of the mechanism of formation, orientation, and location of phases inside thin films of these perovskite materials is essential to optimize their optoelectronic properties. In this contribution I will discuss recent results on the mechanism of crystallization of 2D, 3D and mixed 2D/3D perovskite systems collected by using ex-situ and in-situ X-ray diffraction techniques. I will particularly focus on the mechanism of crystal formation in lead-free tin-based perovskites, highlighting the observed differences with respect to the more studied Pb-based systems. The presented data will show how polymorphic behaviour develops in these systems during drying, leading to formation of highly oriented 3D-like structure together with quasi-2D structure.

14:45 - 15:15
Discussion
PEROPV 1.3
Chair not set
14:05 - 14:15
1.3-T1
Almora, Osbel
Emerging PV Reports in perspective to the Shockley-Queisser Limit.
Almora, Osbel
Authors
Osbel Almora a, Jens Hauch b, Thomas Kirchartz c, Uwe Rau c, Christoph J. Brabec d
Affiliations
a, Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, ES
b, Forschungszentrum Jülich GmbH, Helmholtz‐Institut Erlangen‐Nürnberg for Renewable Energy (IEK‐11), 91058 Erlangen, Germany
c, IEK5-Photovoltaics, Forschungszentrum Jülich, 52425 Jülich, Germany
d, Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
Abstract

Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye‐sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi‐junction PVs. Nevertheless, it can be very time consuming to find or develop an up‐to‐date overview of the state‐of‐the‐art performance for these systems and applications. A recent approach[1] is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters (power conversion efficiency, open-circuit voltage, short-circuit current, fill factor) are provided as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state‐of‐the‐art emerging PVs.

14:15 - 14:25
1.3-T2
Wang, Junke
Eindhoven University of Technology (TU/e)
16.8% Monolithic all-perovskite triple-junction solar cells
Wang, Junke
Eindhoven University of Technology (TU/e), NL
Authors
Junke Wang a, Valerio Zardetto b, Kunal Datta a, Dong Zhang a, b, Martijn Wienk a, René Janssen a, c
Affiliations
a, Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology, partner of Solliance, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
b, TNO, partner of Solliance, High Tech Campus 21, Eindhoven 5656 AE, The Netherlands
c, Dutch Institute for Fundamental Energy Research, De Zaale 20, 5612 AJ Eindhoven, The Netherlands
Abstract

Multijunction solar cells offer an avenue to break the efficiency limit of single-junction devices. By virtue of their cost-effectiveness and widely tunable bandgaps, perovskite semiconductors are attractive for developing all-perovskite multijunction solar cells. To date, tremendous research effort has been made for all-perovskite tandem solar cells, with power conversion efficiencies up to 25.6% reported in small-sized devices.[1] In comparison, all-perovskite triple-junction solar cells that promise higher efficiencies remain largely unexplored.[2-4] Besides design constraints to reduce optical and electrical losses, integrating different perovskite absorber layers in a multijunction cell imposes significant processing challenges. In this contribution, we present a two-step solution process for high-quality 1.73 eV wide-, 1.57 eV mid-, and 1.23 eV narrow-bandgap perovskite films. We achieve power conversion efficiencies of above 19% for monolithic all-perovskite tandem solar cells with limited loss of potential energy and fill factor based on the development of robust and low-resistivity interconnecting layers. In the combination of 1.73 eV, 1.57 eV, and 1.23 eV perovskite sub-cells, we demonstrate a power conversion efficiency of 16.8% for monolithic all-perovskite triple-junction solar cells.[5] Constraints of the current multijunction cell are further discussed.

14:25 - 14:35
1.3-T3
Hidalgo, Juanita
Understanding the Effects of Moisture, Stoichiometry, and Composition on the Texture of Lead Halide Perovskites
Hidalgo, Juanita
Authors
Juanita Hidalgo a, Yu An a, Juan-Pablo Correa-Baena a
Affiliations
a, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, 30332, US
Abstract

Organic-inorganic lead halide perovskites (LHP) are promising materials for photovoltaic applications. The focus has been on compositional optimization of the LHP layer, without much understanding of the effects of the compositional mixing on structure, in particular, on texture. For this reason, it is important to understand the mechanisms that drive textured LHP. This work examines the effect of stoichiometry, composition, and moisture on the structure of LHP by grazing-incidence wide-angle scattering (GIWAXS). In addition, we analyze the effect of texturing in the optoelectronic properties of the material. First, it is shown that for CsMAFAPb(IBr)3 films with an excess organic halide, the exposure to moisture induces a crystallographic re-orientation into the texture in the (001) plane. The re-crystallization enhances the photocurrents and the long-term stability. Second, to examine the individual effect of the A-site cation and X-site halide in these materials, pure and mixed compositions were analyzed. This work shows the importance of understanding what triggers orientation in the structure of LHPs to enhance the electronic properties of the material, especially, charge carrier extraction.

 

 

14:35 - 15:05
Discussion
UPDOWN 1.3
Chair: Lea Nienhaus
14:05 - 14:15
1.3-T1
Wang, Lili
MIT - Massachusetts Institute of Technology
Interfacial Trap-assisted Triplet Generation in Lead Halide Perovskite Sensitized Solid-state Upconversion
Wang, Lili
MIT - Massachusetts Institute of Technology, US
Authors
Lili Wang a, Jason Yoo a, Ting-An Lin b, Cole Perkinson a, Yongli Lu a, Marc Baldo b, Moungi Bawendi a
Affiliations
a, MIT - Massachusetts Institute of Technology, Massachusetts Avenue, 77, Cambridge, US
b, MIT - Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, US, Massachusetts Avenue, 77, Cambridge, US
Abstract

Photon upconversion via triplet-triplet annihilation (TTA) has promise for overcoming the Shockley–Queisser limit for single-junction solar cells by allowing the utilization of sub-bandgap photons. Recently, bulk perovskites have been employed as sensitizers in solid-state upconversion devices to circumvent poor exciton diffusion in previous nanocrystal-sensitized devices. However, an in-depth understanding of the underlying photophysics of perovskite-sensitized triplet generation is still lacking due to the difficulty of precisely controlling interfacial properties of fully solution-processed devices. In this study, interfacial properties of upconversion devices are adjusted by a mild surface solvent treatment, specifically altering perovskite surface properties without perturbing the bulk perovskite. Thermal evaporation of the annihilator precludes further solvent contamination. Counterintuitively, devices with more interfacial traps show brighter upconversion. Approximately an order of magnitude difference in upconversion brightness is observed across different interfacial solvent treatments. Sequential charge transfer and interfacial trap-assisted triplet sensitization are demonstrated by comparing upconversion performance, transient photoluminescence dynamics, and magnetic field dependence of the devices. Incomplete triplet conversion from transferred charges and consequent triplet-charge annihilation (TCA) are also observed. Our observations highlight the importance of interfacial control and provide guidance for further design and optimization of upconversion devices using perovskites or other semiconductors as sensitizers.

14:15 - 14:25
1.3-T2
Imperiale, Christian
University of Toronto
Long-lifetime sensitizers and dimeric annihilators: synergistic considerations for triplet-fusion design
Imperiale, Christian
University of Toronto, CA
Authors
Christian Imperiale a, Mark Wilson a
Affiliations
a, University of Toronto, Department of Chemistry, King's College Road, 10, Toronto, CA
Abstract

I will discuss two orthogonal strategies that pair advances in materials synthesis with photophysical insight to design triplet-fusion upconversion systems with enhanced performance. Firstly, by employing ultrasmall PbS nanocrystals as triplet sensitizers with long (>2μs) excited-state lifetimes, we can achieve large (>1eV) anti-Stokes wavelength shifts to generate photochemically-active excited-state species with near-solar max-efficiency thresholds (~200mW/cm2), even overcoming endothermic triplet sensitization. Secondly, the use of rigid, weakly-coupled dimeric annihilators yields improved performance at low concentrations compared to monomeric annihilators, especially when controlling for triplet transfer and the linear-regime operation threshold.1 Our ongoing work is exploring the expected synergy between these design techniques for high-performance triplet-fusion upconversion.

14:25 - 14:35
1.3-T3
Congreve, Daniel
Volumetric 3D Printing Enabled by Triplet Fusion Upconversion Nanocapsules
Congreve, Daniel
Authors
Daniel Congreve a, b, Samuel Sanders a, Tracy Schloemer a, b, Mahesh Gangishetty a, Daniel Anderson a, Michael Seitz a, b, Chris Stokes a
Affiliations
a, Rowland Institute at Harvard University
b, Stanford University, Stanford, CA 94305, US
Abstract

Three-dimensional (3D) printing has revolutionized additive manufacturing, but the layer-by-layer process of traditional stereolithography can limit resin selection, shape selection, and material quality. One way to achieve volumetric 3D printing, where a vat of polymerizable resin is patterned by light in three dimensions, is to use triplet fusion upconversion (UC). Triplet fusion UC occurs when a sensitizer molecule absorbs low energy light and generates triplet states, which transfer to the annihilator molecules to ultimately generate an excited singlet state that emits higher energy light to initiate polymerization. To ensure excellent light penetration through the vat of resin and maintain the high sensitizer/annihilator concentrations required, the UC materials are encased in silica to generate robust nanocapsules for suspension in the resin. By pairing upconverting nanocapsules and photoinitiators tailored to the upconverted light to commercially available printing resins, we generate prints on the centimeter scale with fine details and no required supports. We further show that the upconversion threshold can be extensively tuned to suit different printing setups. The entire printing process can be performed air-free, opening up new material and geometric opportunities for 3D printing.

14:35 - 15:05
Discussion
15:05 - 15:20
PEROPV Break
15:05 - 15:20
UPDOWN Break
15:15 - 15:20
ORGELE Break
15:15 - 15:20
PEREMER Break
15:15 - 15:20
RETCHEM Opening nanoGe
15:15 - 15:20
SELFNC Opening nanoGe
15:20 - 15:30
ORGELE Session Introduction 1.4
15:20 - 15:30
PEREMER Session Introduction 1.4
15:20 - 15:30
PEROPV Session Introduction 1.4
15:20 - 15:30
RETCHEM Session Introduction 1.1
15:20 - 15:30
SELFNC Session Introduction 1.3
15:20 - 15:30
UPDOWN Session Introduction 1.4
ORGELE 1.4
Chair: James Ryan
15:30 - 15:50
1.4-I1
Ratcliff, Erin
University of Arizona
Multimodal and Multiscale Electrochemical Analysis of Conductive Polymer Electrodes Energy Conversion and Biosensing
Ratcliff, Erin
University of Arizona, US
Authors
Erin Ratcliff a
Affiliations
a, University of Arizona, 1133 E. James E Rogers Way, Tucson, US
Abstract

Conductive polymer electrodes have exceptional promise as active elements in next-generation photon-to-electron-to-molecule processes associated with energy harvesting and storage. A number of electrochemical devices and architectures have been developed, including thermogalvanics, electrochromics, supercapacitors, redox-flow batteries, and photo-electrochemical devices.  Additional applications include biosensors, where recent advancements in emergent wearable health-monitoring devices has inspired the inclusion of conductive polymer as sensing elements on fabrics and textiles, on the skin as electronic tattoos, and in vivo. Understanding the underlying structure-function properties is critical to new technological development.

Despite well-established structural heterogeneity in these systems, conventional macroscopic electroanalytical methods – specifically cyclic voltammetry – are typically used as the primary tool for structure-property elucidation of the polymer/electrolyte interface. This work presents an alternative correlative multi-microscopy strategy; data from laboratory and synchrotron-based micro-spectroscopies, including conducting-atomic force microscopy and synchrotron nanoscale infrared spectroscopy, is combined with potentiodynamic movies of electrochemical fluxes from scanning electrochemical cell microscopy (SECCM) to reveal the relationship between electrode structure and activity at the nanoscale[1]. A combination of electrochemical impedance spectroscopy (EIS), spectroelectrochemistry, and color impedance spectroscopy is used to demonstrate the domain-specific behaviors, including quantification of ion diffusion coefficients [2].    This work serves as a roadmap for benchmarking the quality of conductive polymer films as electrodes, emphasizing the importance of nanoscale electrochemical measurements in understanding macroscopic properties. 

15:50 - 16:10
1.4-I2
Giovannitti, Alexander
Materials Science & Enginereing, Stanford University
Energetic control of redox-active polymers towards safe organic bioelectronic materials
Giovannitti, Alexander
Materials Science & Enginereing, Stanford University, US
Authors
Alexander Giovannitti a
Affiliations
a, Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
Abstract

In my presentation, I will explain the common electrochemical side reactions between redox-active polymeric organic semiconductors and aqueous electrolytes in ambient conditions. We find that electron-rich polymers such as PEDOT:PSS or pg2T-TT[1] can undergo electron transfer reactions with molecular oxygen (oxygen reduction reaction), forming hydrogen peroxide (H2O2) as a side product.  H2O2 itself is an oxidant that can cause harm to biological environments and devices and also impact the device performance such as an increase of the OFF currents of organic electrochemical transistors (OECTs). The origin for the side reaction is an electron transfer reaction from the electron‑rich conjugated polymers to molecular oxygen dissolved in the electrolyte where the ionization potential (IP) of the redox-active polymer determines if the reaction occurs spontaneously. By designing and synthesizing redox-active polymers with large ionization potentials (IP > 4.9 eV)[2], we show that the side reaction can be avoided during the operation of the device in ambient conditions. When tested in the OECT, the materials achieve low OFF currents (nAs), high ON/OFF ratios of >105 and excellent redox-stability during continuous operation. This study elucidates the interaction of redox-active conjugated polymers and molecular oxygen which has previously been overlooked with potentially critical issues for operating electrochemical devices in oxygen-containing aqueous electrolytes (biological environments).

 

16:10 - 16:30
1.4-I3
Ginger, David
University of Washington, US
Coupling Between Ionic and Electronic Transport in Organic Mixed Conductors
Ginger, David
University of Washington, US, US
Authors
David Ginger a
Affiliations
a, University of Washington Clean Energy Institute
Abstract

Conjugated polymers doped with ionic countercharges are being explored for applications ranging from bioelectronics and neuromorphic computing to aqueous supercapacitors and redox flow batteries.  Understanding the chemical and structural factors controlling the injection and transport of ions and charges in these systems has broad applications.  We explore the effects of polymer microstructure and counterion chemistry on ion injection and diffusion using a combination of classic electrochemical and spectroscopic probes with in situ microscopy.  We show that in some polymers, polymer oxidation and ion injection can lead to a structural phase changes, in analogy to doping-induced phase changes in crystalline inorganic materials.  In model conjugated polymers, we combine moving front experiments, NMR, and electronic mobility measurements to compare how electronic carrier mobility, ionic carrier diffusion, and coupled ion/polaron pair mobility all appear to exhibit different, and sometimes counterintuitive changes as a function of polymer microstructure and counterion chemistry.  

16:30 - 16:50
Discussion
PEREMER 1.4
Chair: Maria Antonietta Loi
15:30 - 15:50
Abstract not programmed
15:50 - 16:10
1.4-I1
Dou, Letian
Purdue University
Two-Dimensional Organic-Perovskite Hybrid Materials and Heterostructures
Dou, Letian
Purdue University, US
Authors
Letian Dou a
Affiliations
a, Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA
Abstract

Two-dimensional halide perovskites are exciting new semiconductors that show great promising in low cost and high-performance optoelectronics devices including solar cells, LEDs, photodetectors, transistors, etc. In the first part of this talk, I will present a molecular approach to the synthesis of high-quality organic-inorganic hybrid perovskite quantum wells through incorporating widely tunable organic semiconducting building blocks as the surface capping ligands. By introducing sterically tailored groups into the molecular motif, the strong self-aggregation of the conjugated organic molecules can be suppressed, and single crystalline organic-perovskite hybrid quantum wells and superlattices can be easily obtained via one-step solution-processing. Energy transfer and charge transfer between adjacent organic and inorganic layers are extremely fast and efficient, owing to the atomically-flat interface and ultra-small interlayer distance. Furthermore, this conjugated ligand design greatly enhances materials chemical stability and suppresses halide anion migration. Based on this, we demonstrate for the first time an epitaxial halide perovskite heterostructure with near atomically-sharp interface. Finally, we demonstrate stable and efficient LEDs and FETs using the novel 2D hybrid materials.

16:10 - 16:30
1.4-I2
Schuller, Jon
UC Santa Barbara
Magnetic Dipole Light Emission from Self-Trapped Excitons in Layered 2D Perovskites
Schuller, Jon
UC Santa Barbara
Authors
Jon Schuller a
Affiliations
a, UC Santa Barbara
Abstract

To meet growing data and energy demands, the world is rapidly adopting optoelectronic technologies that use light to power devices, transmit and process information, and help navigate and sense our environment. Recently, solution processable 2D perovskite materials have emerged as an intriguing candidate for inexpensive, scalable, high-performance optoelectronic semiconductors. Here, we destail the recent discovery of completely unexpected magnetic dipole (MD) luminescence in a variety of layered two-dimensional hybrid organic/inorganic perovskites (2D HOIPs). First, we show how to use momentum-resolved spectroscopy techniques to produce model-blind measures of potical constants in 2D pervoskites. We describe how these optical properties can be understood from a metamaterial framework: local atomic-scale inhomogeneities in the classical electromagnetic fields produce strong optical anistotropies and variations between materials that are often incorrectly ascribed to quantum mechanical origins. Next, we demonstrate distinct MD signatures in light emission from 2D HOIPs. This surprising result—the only known example of magnetic dipole emission in an extended material—challenges the universally held assumption that intrinsic optical properties arise from electric dipoles interacting with the electric fields. We conclude by discussing how this unusal light-matter interaction is generated via parity-flipped self-trapped excitons.

16:30 - 16:50
Discussion
PEROPV 1.4
Chair not set
15:30 - 15:50
1.4-I1
Graetzel, Michael
Ecole Polytechnique Federale de Lausanne (EPFL)
Maximizing FAPbI3 Perovskite Solar Cell performance
Graetzel, Michael
Ecole Polytechnique Federale de Lausanne (EPFL), CH

Professor of Physical Chemistry at the Ecole Polytechnique Fédérale de Lausanne (EPFL) Michael Graetzel, PhD, directs there the Laboratory of Photonics and Interfaces. He pioneered research on energy and electron transfer reactions in mesoscopic systems and their use to generate electricity and fuels from sunlight. He invented mesoscopic injection solar cells, one key embodiment of which is the dye-sensitized solar cell (DSC).  DSCs are meanwhile commercially produced at the multi-MW-scale and created a number of new applications in particular as lightweight power supplies for portable electronic devices and in photovoltaic glazings. They engendered the field of perovskite solar cells (PSCs) that turned our to be the most exciting break-through in the recent history of photovoltaics. He received a number of prestigious awards, of which the most recent ones include the RusNANO Prize, the Zewail Prize in Molecular Science, the Global Energy Prize, the Millennium Technology Grand Prize, the Samson Prime Minister’s Prize for Innovation in Alternative Fuels, the Marcel Benoist Prize, the King Faisal International Science Prize, the Einstein World Award of Science and the Balzan Prize. He is a Fellow of several learned societies and holds eleven honorary doctor’s degrees from European and Asian Universities. According to the ISI-Web of Science, his over 1500 publications have received some 230’000 citations with an h-factor of 219 demonstrating the strong impact of his scientific work.

 

Authors
Michael Graetzel a
Affiliations
a, EPFL, Switzerland
Abstract

Metal halide perovskites of the general formular ABX3 where A is a monovalent cation such as caesium, methylammonium or formamidinium, B stands for divalent lead, tin or germanium and X is a halide anion, have shown great potential as light harvesters for thin film photovoltaics. Amongst a large number of compositions investigated, the cubic α-phase of formamidinium lead triiodide (FAPbI3) has emerged as the most promising semiconductor for highly-efficient and stable perovskite solar cells (PSCs). Maximizing the performance of α-FAPbI3 has therefore become of vital importance for the perovskite research. Using a new ion engineering concept to mitigate lattice defects and to augment film crystallinity, we attain a power conversion efficiency of 25.6 % (certified 25.2%), long-term operational stability, and intense electroluminescence with external quantum efficiencies over 10%. Our findings provide a facile access to solution processable films with unprecedented opto-electronic performance.

15:50 - 16:10
1.4-I2
Huang, Jinsong
University of North Carolina – Chapel Hill
Progress of p-i-n structure solar cells and minimodules development
Huang, Jinsong
University of North Carolina – Chapel Hill, US
Authors
Jinsong Huang a
Affiliations
a, The University of North Carolina at Chapel Hill, Department of Applied Physical Sciences, East Cameron Avenue, 145, Chapel Hill, US
Abstract

I am going to present our progress in advancing the performance of p-i-n structure solar cells and how to convert them into efficient minomodules by scalable blading method with minimal cell-to-module derate. The efficiency and stability enhancements come from the fundamental understanding of defect structures in perovskite films made by solution process (1), degradation of precursor during storage and fabrication process (2).  The self-doping of perovskite is also important in affecting the charge recombination process in perovskites (3).  Strategies that tackle both morphology defects and unintentional excessive doping will be introduced (2-4). The efficiency of p-i-n structure perovskite solar cells is still lagging behind those of n-i-p structures. I will give a brief analysis of their origin and explore the approaches to bridge the gap.  

 

1.  Resolving spatial and energetic distributions of trap states in metal halide perovskite solar cells, Zhenyi Ni, Chunxiong Bao, Ye Liu, Qi Jiang, Wu-Qiang Wu, Shangshang Chen, Xuezeng Dai, Bo Chen, Barry Hartweg, Zhengshan Yu, Zachary Holman, Jinsong Huang*, Science, Vol. 367, Issue 6484, pp. 1352-135.

2. Iodine Reduction for Reproducible and High Performance Perovskite Solar Cells and Modules , Shangshang Chen, Xun Xiao, Hangyu Gu, Jinsong Huang*, Science Advances, In press

3. Reduced Self-doping of Perovskites Induced by Short Annealing for Efficient Solar Modules, Yehao Deng, Zhenyi Ni, Axel F. Palmstrom, Jingjing Zhao, Shuang Xu, Charles H. Van Brackle, Xun Xiao, Kai Zhu, Jinsong Huang*, Joule, DOI: 10.1016/j.joule.2020.07.003 (2020)

4. Identifying the Soft Nature of Defective Perovskite Surface Layer and Its Removal Using a Facile Mechanical Approach, Shangshang Chen, Ye Liu, Xun Xiao, Zhenhua Yu, Yehao Deng, Xuezeng Dai, Zhenyi Ni, and Jinsong Huang*, Joule, Volume 4, Issue 12, 16 December 2020, Pages 2661-2674

16:10 - 16:30
1.4-I3
Zhu, Kai
National Renewable Energy Laboratory, Golden, Colorado
Two-Dimensional Perovskite Passivation Agent Engineering for Efficient Tandem Solar Cells
Zhu, Kai
National Renewable Energy Laboratory, Golden, Colorado, US

Kai Zhu is currently a senior scientist in the Chemistry and Nanoscience Center at the National Renewable Energy Laboratory (NREL). He received his PhD degree in physics from Syracuse University in 2003. Before this position, he worked as a postdoctoral researcher in the Basic Science Center at NREL, focusing on fundamental charge carrier conduction and recombination in photoelectrochemical cells, especially dye-sensitized solar cells. Dr. Zhu’s research on dye-sensitized solar cells involves the development of advanced electrode materials/architectures, basic understanding of charge transport and recombination processes in these electrodes, and thin-film solar cell development/characterization/modeling. His recent research has centered on both basic and applied research on perovskite solar cells, including perovskite material development, device fabrication and characterization, and basic understanding of charge carrier dynamics in these cells. In addition to solar conversion applications, his research interests have also included III-Nitride wide-bandgap semiconductors for high-power blue and UV light emitting diodes and ordered nanostructured electrodes for Li-ion batteries and supercapacitors.

Authors
Kai Zhu a
Affiliations
a, Chemical and Nanoscience Center, National Renewable Energy Laboratory (NREL), Evergreen, Colorado 80401, EE. UU., Evergreen, US
Abstract

Perovskite solar cells (PSCs) have become a competitive photovoltaic (PV) technology with rapid progress of efficiencies reaching a certified 25.5% for single-junction devices. The bandgap tunability through perovskite composition engineering is attractive for developing ultrahigh-efficiency tandem solar cells, including perovskite/perovskite, perovskite/silicon, or perovskite/thin-film absorber (e.g., CIGS). Toward this end, highly efficient wide-bandgap and low-bandgap perovskites solar cells need to be development. In this talk, I will discuss our recent progress on suppressing defects in perovskites covering both the wide-bandgap (~1.7–1.8 eV) and low-bandgap (~1.2–1.3 eV) perovskite compositions. Specifically, strategies on utilizing 2D perovskite passivation agents (2D-PPA) will be discussed. 2D perovskites are normally based on bulky organic cations (e.g., butylammonium or phenethylammonium), which are hydrophobic and can prevent device degradation associated with moisture intrusion. Using 2D-PPA to modify 3D perovskite (e.g., grain or film surface) represents an effective approach to not only increase the device stability, but also improve cell efficiency under certain processing conditions. Tuning precursor chemistry and growth conditions with 2D-PPAs affect significantly the physical and optoelectronic properties of perovskites. Applications of perovskite absorbers in highly efficient tandem devices will be discussed.

16:30 - 16:50
Discussion
RETCHEM 1.1
Chair not set
15:30 - 15:50
1.1-I1
Kaskel, Stefan
Technische Universität Dresden
Lithium Sulfur Batteries: Chemistry, Materials and Cell Production
Kaskel, Stefan
Technische Universität Dresden, DE
Authors
Stefan Kaskel a, Holger Althues b, Susanne Doerfler b, Benjamin Schumm b, Thomas Abendroth b
Affiliations
a, Department of Chemistry, TU Dresden
b, Fraunhofer IWS Dresden
Abstract

Lithium sulfur batteries are considered as the next generation batteries due to their high gravimetric energy density approaching 500 Wh/kg. Sulfur is an inexpensive cathode material. The chemistry of sulfur conversion is significantly affected by the type of electrolyte used. New electrolytes suppressing polysulfide dissolution are advantageous to reduce the shuttle effect and hence achieve long cycling stability. New electrolytes furthermore can operate without LiNO3, a common additive in ether-based electrolyte systems leading to gas formation inside the cell. The continuous production of thin lithium metal anodes is another promising new technology to achieve high specific energy on real cell level. But also alternative anode materials such as hard carbons are promising to achieve long cycling stabilities. They can be even used to realize room temperature sodium sulfur batteries. On the cathode side the design of highly porous carbons reaching specific surface areas of up to 3000 m2/g is a key requisite to achieve high sulfur loading and utilization. New nitrogen-doped carbons enhance the affinity towards polysulfides and reduce shuttle effects. Moreover, the electrocatalytic sites increase the conversion rate and act as nucleation centers for homogeneous Li2S precipitation inside the porous carbon matrix. The presentation will give insights into continuous electrode production, laser cutting, silicon anode integration and real world pouch cell production.

15:50 - 16:10
1.1-I2
Dinca, Mircea
Massachusetts Institute of Technology (MIT)
Anisotropic Transport in 2D Electrically Conducting Metal-Organic Frameworks
Dinca, Mircea
Massachusetts Institute of Technology (MIT), US
Authors
Mircea Dinca a, Grigorii Skorupskii a, Dong-Gwang Ha a, Jin-Hu Dou a, Robert Day a
Affiliations
a, MIT - Massachusetts Institute of Technology, Massachusetts Avenue, 77, Cambridge, US
Abstract

Metal-Organic Frameworks featuring stcked two-dimensional sheets made of organic ligands, typically trigonal, and square-planar metals are the latest addition to

van der Waals materials with interesting electronic properties. Understanding and controlling charge transport in these

materials has been challenging because single crystals are typically difficult to grow. Here, we will present

efforts towards growing single crystals of a series of 2D MOFs, spanning different growth techniques[1,2] and

different materials where both the metal ion and the organic ligands are changed [3]. We show that transport

normal to the 2D plane is significantly higher than anticipated and provide evidence for metallicity in certain of

these structures [4].

16:10 - 16:30
1.1-I3
Cohen, Seth
U.C. San Diego
Strategies for Preparing Ultrathin MOF Membranes
Cohen, Seth
U.C. San Diego, US
Authors
Seth Cohen a, Jinyeong Kim a, Yuji Katayama a, Kyle Barcus a
Affiliations
a, Department of Chemistry and Biochemistry, U.C. San Diego, La Jolla, CA 92093 USA
Abstract

Hybrid materials of metal-organic frameworks (MOFs) and polymers have gained interest as processible composites that might be suitable for a wide range of applications, including energy technologies. A number of mixed-matrix membranes (MMMs) prepared with MOFs, as well as polymer-decorated MOF particles have been reported in the literature. Combining these two areas of investigation, the use of polymer-decorated MOF particles to prepare ultrathin MOF-polymer composite membranes is described. Under specific conditions, some MOF-polymer particle membranes are found to self-assemble into highly ordered arrays. Free-standing membranes that are only one particle layer thick have been prepared. In addition, the controlled assembly and preferred orientation of MOF crystallites within a polymer matrix has been achieved. All of these materials are prepared via a common water interface casting method. The preparation and characterization of these interesting hybrid materials will be presented and discussed.

16:30 - 16:50
Discussion
SELFNC 1.3
Chair: Dmitry Baranov
15:30 - 15:50
1.3-I1
Kagan, Cherie
University of Pennsylvania
Designing Au Nanocrystal Assemblies for Optical Metamaterials
Kagan, Cherie
University of Pennsylvania, US
Cherie R. Kagan is the Stephen J. Angello Professor of Electrical and Systems Engineering, Professor of Materials Science and Engineering, and Professor of Chemistry at the University of Pennsylvania. Kagan graduated from the University of Pennsylvania in 1991 with a BSE in Materials Science and Engineering and a BA Mathematics. She earned her PhD in Materials Science and Engineering from the Massachusetts Institute of Technology in 1996 working with Moungi G. Bawendi. In 1996, she went to Bell Labs as a postdoctoral fellow and in 1998, she joined IBM’s T. J. Watson Research Center, where she most recently managed the “Molecular Assemblies and Devices Group.” In 2007, she joined the faculty of the University of Pennsylvania. Kagan is an Associate Editor of ACS Nano and serves on the editorial boards of Nano Letters and NanoToday. The Kagan group’s research interests are in the chemical and physical properties of nanostructured and organic materials and in integrating these materials in electronic, optoelectronic, optical, thermoelectric and bioelectronic devices. The group combines the flexibility of chemistry and bottom-up assembly with top-down fabrication techniques to design novel materials and devices. The group explores the structure and function of these materials and devices using spatially- and temporally-resolved optical spectroscopies, AC and DC electrical techniques, electrochemistry, scanning probe and electron microscopies and analytical measurements. Kagan is co-director of The Penn Center for Energy Innovation and serves on the World Economic Forum, Global Agenda Council on Nanotechnology; on the Department of Energy, Basic Energy Sciences Materials Council; and on the advisory board of the US Summer Schools in Condensed Matter and Materials Physics. She served on the Materials Research Society’s Board of Directors from 2007-2009 and the editorial board of the ACS Applied Materials and Interfaces from 2008-2011
Authors
Cherie Kagan a
Affiliations
a, University of Pennsylvania, 200 South 33rd Street, Philadelphia, 19104, US
Abstract

We report the use of colloidal Au NCs as building blocks in the design of optical metamaterials. Chemical exchange of the long ligands used in NC synthesis with more compact ligand chemistries brings neighboring NCs into proximity and increases interparticle coupling.1,2 This ligand-controlled coupling allows us to tune through a dielectric-to-metal phase transition seen by a 1010 range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies.1 For example, by partially exchanging the NC assemblies, we create strong, ultrathin film optical absorbers with a 6x increase in extinction in the infrared compared to that of bulk Au thin films.2 For more complete ligand exchange and with thermal annealing, we realize strong optical scatterers useful in the design of optical metamaterials.3 Ligand exchange and annealing of NC films also triggers a large volume shrinkage. By juxtaposing plasmonic NCs and bulk materials, we exploit their different chemical and mechanical properties to transform lithographically-defined two-dimensional structures, upon ligand exchange, into three-dimensional structures.4 We use the three-dimensional structures to demonstrate large-area metamaterials with chiroptical responses of ~40% transmission difference between left-hand and right-hand circularly polarized light and that are suitable broadband circular polarizers.5

15:50 - 16:10
1.3-I2
Smilgies, Detlef-M.
Binghamton University
Self-Assembly of Facetted Nanocrystals – the Importance of the Ligand Shell
Smilgies, Detlef-M.
Binghamton University, US

Detlef Smilgies studied physics at Goettingen University in Germany and received a Ph. D. in surface science at the Max-Planck-Institute for Fluid Dynamics, Goettingen in 1991. After postdocs in the US and in Denmark, he worked as a beamline scientist at the European Synchrotron Radiation Facility in Grenoble, France and at the Cornell High Energy Synchrotron Source in Ithaca, NY, USA. He presently is a visiting scientist at Binghamton University and an adjunct professor of chemical engineering at Cornell University. His research interests are in self-assembly in thin films of soft materials, nanoscience, organic electronics, and materials processing from the liquid phase using real-time in-situ grazing-incidence x-ray scattering.

Authors
Detlef-M. Smilgies b
Affiliations
a, Materials Science and Engineering Program, SUNY Binghamton, Binghamton NY 13902, USA
b, Chemical and Biomolecular Engineering, Cornell University, Ithaca NY 14850, USA
Abstract

Thanks to tremendous progress in synthesis methods, quasi-monodisperse nanocrystals can be synthesized in an abundance of shapes. Here we will discuss particles with well-defined facets formed by close-packed crystallographic planes. It is tempting to describe the packing of such nanocrystal assemblies as the packing of hard polyhedra. However for particles in the size range of 2-10 nm, the ligands, commonly alkyl chains of 1.5 to 2 nm lengths, cannot be ignored. On facets ligands can pack closely, as is typical for alkyl chain monolayers. However, at edges and corners between adjacent facets there is not enough space to anchor a sufficient number of ligand head groups, in order for the ligand chains to fill space as densely as on the facets. This simple model of an anisotropic ligand shell can explain some of the unexpected nanocrystal packings that have been observed experimentally.

16:10 - 16:30
1.3-I3
Yin, Yadong
Department of Chemistry, University of California Riverside, United States.
All-Scale Assembly and Precise Positioning of Colloidal Nanostructures
Yin, Yadong
Department of Chemistry, University of California Riverside, United States., US
Authors
Yadong Yin a
Affiliations
a, University of California Riverside, Big Springs Road, 501, Riverside, US
Abstract

After nearly three decades of effort, it is now possible to synthesize nanostructured materials of well-controlled composition, size, surface functionalization, and physical properties. The next phase of nanotechnology development is the controlled assembly of nanoscale building blocks into desired superstructures up to bulk dimensions and precise positioning them at the desired locations, which, however, remain key challenges due to the lack of effective tools and mechanisms. In this presentation, we report our recent progress in this direction. We first describe the self-assembly of uniform superstructures at all scales using an emulsion-based template-assisted self-assembly strategy. This new strategy is designed by taking advantage of the partial miscibility of the solvent mixture, which makes it possible to generate transient emulsion droplets containing the target building blocks and carry them into templating holes patterned on a substrate, producing well-defined superstructures with the positional order defined by the template. This strategy is simple, low-cost, high-throughput, and scalable, and it demonstrates high controllability and general applicability in producing superstructures. Secondly, we report an Electric Field-Assisted Surface-Sorption nano-Printing (EFASP) method to allow fast, nanometer-precision printing of nanoparticles over large areas with high reproducibility. As an additive nanofabrication method, it utilizes a tip-based high-voltage writing process to generate nanoscale de-fluorinated patterns in a fluorinated surface, which not only enables electrostatic trapping but also creates a high local surface potential in contrast to the fluorinated area. As a result, the method combines dielectrophoretic enrichment and deep surface-energy modulation, featuring high efficiency and extraordinary robustness of nanoparticle printing. The method also supports the combinatorial pattern of multiple functional nanoparticles for realizing multi-color printing by conveniently repeating the writing and assembly cycles.

16:30 - 16:50
Discussion
UPDOWN 1.4
Chair: Mark Wilson
15:30 - 15:50
1.4-I1
Castellano, Felix
North Carolina State University
Photochemical Upconversion using Transition Metal Photosensitizers Spanning the d-Block
Castellano, Felix
North Carolina State University, US

Felix (Phil) Castellano earned a B.A. in Chemistry from Clark University in 1991 and a Ph.D. in Chemistry from Johns Hopkins University in 1996. Following an NIH Postdoctoral Fellowship at the University of Maryland, School of Medicine, he accepted a position as Assistant Professor at Bowling Green State University in 1998. He was promoted to Associate Professor in 2004, to Professor in 2006, and was appointed Director of the Center for Photochemical Sciences in 2011. In 2013, he moved his research program to North Carolina State University where he is currently the Goodnight Innovation Distinguished Chair. He was appointed as a Fellow of the Royal Society of Chemistry (FRSC) in 2015. His current research focuses on metal-organic chromophore photophysics and energy transfer, photochemical upconversion phenomena, solar fuels photocatalysis, energy transduction at semiconductor/molecular interfaces, photoredox catalysis, and excited state electron transfer processes.     

Authors
Felix Castellano a
Affiliations
a, Department of Chemistry, NC State University, Raleigh, NC 27695-8204
Abstract

Transition metal-based photosensitizers are of significant value for promoting numerous light-activated processes and chemical transformations relying on excited state electron and energy transfer reactions. Historically, the most extensively used inorganic photosensitizers have been confined to nd6 (n = 3, 4, or 5) electron configurations and their associated metal-to-ligand charge transfer (MLCT) excited states. This presentation will discuss the unique and somewhat unexpected photochemistry and photophysics in a number of distinct transition-metal containing photosensitizers derived from earth-abundant elements spanning the transition block. In some instances, ligand-to-metal charge transfer (LMCT) states dominate excited state decay, while long-lived MLCT excited states have been successfully engineered in others. These designer, earth-abundant chromophores have been implemented in a variety of photoactivation schemes harnessing photochemical upconversion to generate light, initiate free-radical polymerization chemistry, promote photoredox chemistry, and enable photocatalytic chemo-thermal energy storage schemes. Representative examples illustrating these photo-processes will be highlighted.  

15:50 - 16:10
1.4-I2
Huang, Libai
Purdue University
Exciton Transport in Singlet Fission Materials: a New Hare and Tortoise Story
Huang, Libai
Purdue University, US
Authors
Libai Huang a
Affiliations
a, Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
Abstract

Singlet fission is promising for redistributing solar spectrum to overcome the Shockley-Queisser limit for single junction solar cells using molecular materials. Despite recent experimental and theoretical advances in understanding the underlying mechanisms, how exciton transport is coupled to singlet fission dynamics is much less explored. Here we examine exciton transport in singlet fission materials, highlighting the use of transient absorption microscopy (TAM) to track the population of different states in both spatial and temporal domains. In contrast to the conventional picture where singlet and triplet excitons migrate independently, TAM measurements of acene single crystals reveal cooperative transport between fast-moving singlet and slow-moving triplet excitons. Such cooperative transport is unique to singlet fission materials and allows hundreds of nanometers triplet migration on the nanosecond timescale, beneficial for solar cell applications. The transport of triplet pair intermediates and general criteria for achieving cooperative singlet-triplet transport are also discussed.

16:10 - 16:30
1.4-I3
Tang, Ming Lee
University of California Riverside
Towards photon upconversion in thin films with CdSe nanocrystal light absorbers
Tang, Ming Lee
University of California Riverside, US
Authors
Ming Lee Tang a
Affiliations
a, University of California, Riverside
Abstract

In order to step towards functional photon- upconverting thin films for solar and medical applications, efficient triplet energy transfer in solution should be translated to the solid state. In this process, many drawbacks to practical applications, such as volatile/ toxic organic solvents and long-term stability of the thin film, have to be be addressed. Our CdSe quantum dot photosensitized thin film has photon upconversion quantum yields (QYs) in solid state of over 2% with the best spot giving over 6% (Photon upconversion QYs are out of a maximum of 50%). By embedding the QDs and molecular emitters in a phosphorescent host, poly(9-vinylcarbazole), we eliminate volatile organic solvents and avoid the spontaneous crystallization of the emitter, thus addressing several challenges to practical applications. Analysis of thin-film morphology provides insight into further improving the photon upconversion QY.

16:30 - 16:50
Discussion
17:00 - 18:30
ePoster Session
 
Fri Mar 12 2021
10:30 - 10:35
ORGELE Opening nanoGe
10:30 - 10:35
PEROPV Opening nanoGe
10:30 - 10:35
RETCHEM Opening nanoGe
10:30 - 10:35
SELFNC Opening nanoGe
10:30 - 10:35
UPDOWN Opening nanoGe
10:35 - 10:45
ORGELE Session Introduction 2.1
10:35 - 10:45
PEROPV Session Introduction 2.1
10:35 - 10:45
RETCHEM Session Introduction 2.1
SELFNC 2.1
Chair: Dmitry Baranov
10:35 - 10:45
2.1-T1
Maier, Andre
University of Tübingen
The effect of long-range order on charge transport in self-assembled nanocrystal and nanocluster superlattices
Maier, Andre
University of Tübingen, DE
Authors
Andre Maier a, Florian Fetzer a, Olympia Geladari a, Philipp Frech a, Kai Braun a, Monika Fleischer a, Frank Schreiber a, Andreas Schnepf a, Marcus Scheele a, Dmitry Lapkin b, Nastasia Mukharamova b, Ivan Vartanyants b, Martin Hodas a
Affiliations
a, University of Tübingen, Auf der Morgenstelle, Tübingen, DE
b, DESY - Deutsches Elektronen-Synchrotron, Hamburg, Notkestraße, 85, Hamburg, DE
Abstract

The self-assembly of nanoparticulate building blocks into superlattices with long-range order bear immense potential for customized materials with novel structure-related properties by design. However, such structure-transport relationships have remained unenlucidated so far. We present correlative studies of the structure and transport properties of highly defined superlattices of two state-of-the-art model systems.

First, electric transport measurements and synchrotron-based X-ray nanodiffraction are performed on PbS nanocrystal superlattices.[1,2] This allows us to fully characterize the superlattice symmetry and nanocrystal orientation in direct correlation with the charge transport properties. We found strong evidence for a beneficial effect of the crystallinity on charge transport, and we reveal a charge transport anisotropy in long-range ordered monocrystalline superlattices based on the dominant effect of shortest interparticle hopping distances. We suggest that this is an inherent feature of weakly coupled superlattices.

Second, we report the first structure-transport correlation study of gold nanocluster exhibiting semiconducting behavior.[3] The conductivity of long-range ordered crystalline domains of self-assembled Au32 nanocluster exceeds that of glassy assemblies of the same nanoclusters by two orders of magnitude. Accompanied with emerging optical transitions, this points to an enhanced electronic coupling in highly ordered superlattices, attributed to a vanishing degree of structural and energetic disorder

10:45 - 10:55
2.1-T2
Mattiotti, Francesco
Thermal Decoherence of Superradiance in Lead Halide Perovskite Nanocrystal Superlattices
Mattiotti, Francesco
Authors
Francesco Mattiotti a, b, c, Masaru Kuno d, Fausto Borgonovi b, c, Boldizsár Jankó a, G. Luca Celardo e
Affiliations
a, Department of Physics, University of Notre Dame, US
b, Dipartimento di Matematica e Fisica and Interdisciplinary Laboratories for Advanced Materials Physics, Universita Cattolica del Sacro Cuore, Brescia, Italy
c, Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia, Italy
d, Department of Chemistry, University of Notre Dame, US
e, Instituto de Física, Benemérita Universidad Autónoma de Puebla, Puebla, Pue. 72570
Abstract

Recent experiments by Rainò et al. (Nature 2018, 563, 671−675) have documented cooperative emission from CsPbBr3 nanocrystal superlattices, exhibiting the hallmarks of low-temperature superradiance. In particular, the optical response is coherent and the radiative decay rate is increased by a factor of 3, relative to that of individual nanocrystals. However, the increase is 6 orders of magnitude smaller than what is theoretically expected from the superradiance of large assemblies, consisting of 106 −108 interacting nanocrystals. Here, we develop a theoretical model of superradiance for such systems and show that thermal decoherence is largely responsible for the drastic reduction of the radiative decay rate in nanocrystal superlattices. Our theoretical approach explains the experimental results (Nature 2018, 563, 671−675), provides insight into the design of small nanocrystal superlattices, and shows a 4 orders of magnitude enhancement in superradiant response. These quantitative predictions pave the path toward observing superradiance at higher temperatures.

10:55 - 11:05
2.1-T3
Marino, Emanuele
University of Pennsylvania
Controlled Deposition of Nanocrystals with Critical Casimir Forces
Marino, Emanuele
University of Pennsylvania, US
Authors
Emanuele Marino a, b, Oleg A. Vasilyev c, Bas B. Kluft b, Milo J.B. Stroink b, Svyatoslav Kondrat c, Peter Schall b
Affiliations
a, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104–6323, USA
b, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands, NL
c, Max Planck Institute for Intelligent systems
Abstract

Nanocrystal assembly represents the key fabrication step to develop next-generation optoelectronic devices with properties defined from the bottom-up. Despite numerous efforts,
our limited understanding of nanoscale interactions has so far delayed the establishment of assembly conditions leading to reproducible superstructure morphologies, therefore hampering integration with large-scale, industrial processes. In this talk, I will illustrate the deposition of a layer of semiconductor nanocrystals on a flat and unpatterned silicon substrate as mediated by the interplay of critical Casimir attraction and electrostatic repulsion. Through experimental work rationalized with Monte Carlo and molecular dynamics simulations, I will show how this assembly process can be biased towards the formation of 2D layers or 3D islands and how the morphology of the deposited superstructure can be tuned from crystalline to amorphous. Our findings demonstrate the potential of the critical Casimir interaction to direct the growth of future artificial solids based on nanocrystals as the ultimate building blocks.

References: 

[1]  Emanuele Marino, Oleg A. Vasilyev, Bas B. Kluft, Milo J.B. Stroink, Svyatoslav Kondrat, and Peter Schall, ''Controlled Deposition of Nanoparticles with
Critical Casimir Forces", Under review (2021).

[2] Oleg A. Vasilyev, Emanuele Marino, Bas B. Kluft, Peter Schall, and Svyatoslav Kondrat, "Debye vs Casimir: Controlling the Structure of Charged Nanoparticles Deposited On a Substrate", Under review (2021).

11:05 - 11:15
2.1-T4
Toso, Stefano
Istituto Italiano di Tecnologia - IIT
Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals
Toso, Stefano
Istituto Italiano di Tecnologia - IIT
Authors
Stefano Toso a, b, Dmitry Baranov a, Davide Altamura c, Francesco Scattarella c, Jakob Dahl d, e, Xingzhi Wang d, e, Sergio Marras f, A. Paul Alivisatos d, e, g, Andrej Singer h, Cinzia Giannini c, Liberato Manna a
Affiliations
a, Nanochemistry Department, Italian Institute of Technology, Italy, Via Morego, 30, Genova, IT
b, International Doctoral Program in Science, Università Cattolica del Sacro Cuore, Italy, 25121 Brescia, Italia, Brescia, IT
c, Istituto di Cristallografia, Consiglio Nazionale delle Ricerche, via Amendola 122/O, 70126 Bari, Italy
d, University of California Berkeley, Department of Chemistry, US
e, Material Sciences Division, Lawrence Berkeley National Laboratory, US, Berkeley, California 94720, US
f, Materials Characterization Facility, Italian Institute of Technology, Italy
g, Kavli Energy NanoSciences Institute at Berkeley, US
h, Cornell University, Department of Materials Science and Engineering, Ithaca, NY 14853, USA, Ithaca, US
Abstract

Colloidal nanocrystal superlattices are highly ordered aggregates of particles. Crystals are highly ordered aggregates of atoms. However, nanocrystal superlattices are not conventionally considered crystals. But where does the border lie? Previously, we reported that CsPbBr3 nanocrystal superlattices have a structural perfection comparable with that of epitaxially grown multilayers, which can be considered as full-fledged single-crystals.[1]

In our most recent work, we discuss a novel approach to the characterization of periodically stacked colloidal nanocrystals, which was inspired by diffraction experiments on multilayers grown by molecular beam epitaxy.[2,3] Our method takes advantage of optical interference phenomena arising from the superlattice periodicity, which enrich the profile of Bragg peaks in structural information. By fitting these profiles, acquired with a common lab-grade diffractometer, we can extract structural information that usually requires high-end setups such as synchrotron to be collected. Our approach is versatile and works well for faceted nanocrystals, but it is especially suitable for nanoplatelets and nanosheets, that easily assemble into stacked periodic structures thanks to their highly anisotropic shape. Moreover, we expect that the multilayer diffraction method can be also extended 2D-layered organic-inorganic materials, which are not considered superlattices but share with them the periodic alternation of different layers.

To demonstrate our approach, we analyzed nanoplatelets of CsPbBr3 and PbS, and measured with high precision thickness, interparticle distance and even distortions in their atomic lattice. In addition, we demonstrated that such nanocrystal superlattices reach stacking displacements as small as 0.3-0.5 Å. This is comparable with atomic displacement parameters found in metal-organic bulk crystals, leading to intriguing questions. For example, how different is a stacking of perovskite nanoplatelets from a bulk crystal of a hybrid Ruddlesden-Popper perovskite? Can we study nanocrystal superlattices as they were bulk crystals? In the end, are nanocrystal superlattices a new class of hybrid organic-inorganic bulk crystals?

11:15 - 11:45
Discussion
UPDOWN 2.1
Chair: Victor Gray
10:35 - 10:45
2.1-T1
Sharma, Abhinav
University of New South Wales, School of Photovoltaics and Renewable Energy Engineering
Design requirements imposed on solar energy conversion concepts by sparse solar photon flux
Sharma, Abhinav
University of New South Wales, School of Photovoltaics and Renewable Energy Engineering, AU
Authors
Abhinav Sharma a, Andreas Pusch a, Michael Nielsen a, Udo Roemer a, Murad Tayebjee a, Fiacre Rougieux a, Nicholas Ekins-Daukes a
Affiliations
a, 1School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, Australia
Abstract

Efficiently utilising near infrared (NIR) solar radiation remains a challenge in advanced solar energy conversion concepts for photocatalysis and photovoltaics. Here we argue that the particulate nature of the solar photon flux limits the efficiency of devices that require interactions between excitations to exploit low energy photons, such as in upconversion and hot carrier systems.

Energy transfer ranges, absorber cross-sections, and excitation lifetimes determine a spatial and temporal extent within which photons must be absorbed. Given an incoming photon flux, that extent needs to be large enough to encompass multiple photons to allow for efficient operation. If the interaction length and time scales in a device are too short, the photon flux from the sun may be too sparse for efficient solar energy conversion. We explore the literature for parameters pertaining to current technologies and present a quantitative indication of the extent to which they are limited by the sparse solar photon flux. Finally, we describe the role emerging strategies such as hybrid schemes and phononic (vibrational) engineering will play in bridging the gap between current devices and their efficiency limit

10:45 - 10:55
2.1-T2
Sawhney, Nipun
University of Cambridge
The Interplay of Entropy, Traps and Activation Energies in Endothermic Singlet Fission
Sawhney, Nipun
University of Cambridge, GB

I am Nipun Sawhney, a PhD student at the University of Cambridge, currently focusing on studying endothermic singlet fission in organic materials, triplet energy transfer and its applications in solar energy. I study the thermodynamics and photophysics of excitons in these materials using time resolved spectroscopy. 

Authors
Nipun Sawhney a, Raj Pandya a, Arya Thampi a, David Palecek a, Edoardo Ruggeri a, Akshay Rao a
Affiliations
a, Optoelectronics Group, Department of Physics, University of Cambridge
Abstract

Singlet fission (SF), in Tetracene and its derivatives, has been investigated extensively [1]. Singlet and triplet energies in these materials are favourable for down-conversion of light for use in solar energy applications. However, the nature of singlet fission, the role of entropy, traps, morphology and activation energies is still poorly understood, with little consensus across the scientific community. We investigate the role of entropy, traps and activation energies in endothermic singlet fission, using well-studied acenes such as TIPS-Tetracene and Tetracene. Using pump-probe spectroscopy, we observe singlet fission dynamics through more than ten orders of time (Femto to microsecond) in films of these materials. We find a strong correlation of morphology of TIPS-Tetracene films with trap creation and study its effect on the entropic drive in endothermic singlet fission. We contrast this with Tetracene film observations to fill gaps in the traditional understanding of singlet fission dynamics, notably observing and attempting to explain how Tetracene and TIPS-Tc, both endothermic SF materials, continue to produce triplets upon excitation even at very low temperatures.

We find a high degree of correlation between the existence of trap states, emissive decay (loss) pathways, varying magnetic field effects on photoluminescence and singlet fission efficiencies. A low activation energy barrier, throughout the process of SF, is observed with traps appearing to play a deciding role on SF efficiencies. This result is compounded by our initial observations of morphology dependent singlet fission in TIPS-Tc, wherein moving from one morphology to another, allows for an `apparent` 2 order (100 times) increase in SF rates. These results in conjunction with time-resolved photoluminescence help us resolve trap state emission kinetics and spectra from singlet emission and the singlet fission process.

Using temperature-dependent transient absorption spectroscopy at the femtosecond, picosecond, nanosecond and microsecond time scales, we map activation energy barriers, observe the relative energetics of traps, and study the role of entropy in endothermic singlet fission in a multitude of morphologies and films of the TIPS-Tetracene and Tetracene materials. Further, we critically analyse traditional markers of singlet fission and the veracity of the current understanding of endothermic singlet fission`s morphology dependence, rate-limiting steps, the role of intermediary states and thermodynamics of the process and provide our insights for the same.

 

 

10:55 - 11:05
2.1-T3
Börjesson, Karl
University of Gothenburg
Annihilation vs. Excimer Formation by the Triplet Pair in Triplet-Triplet Annihilation Photon Upconversion
Börjesson, Karl
University of Gothenburg, SE
Authors
Karl Börjesson a
Affiliations
a, University of Gothenburg, kemivaegen 10, Gothenburg, SE
Abstract

The triplet pair is the key functional unit in triplet-triplet annihilation photon upconversion. The same molecular properties that stabilize the triplet pair, also allow dimers to form on the singlet energy surface, creating an unwanted energy relaxation pathway. I will show that excimer formation in perylene systems most likely is a consequence of a triplet dimer formed before the annihilation event.[1] Alkyl substitution of perylene can suppress excimer formation, but decelerate triplet energy transfer and triplet-triplet annihilation at the same time. I will show that mono-substitution with small alkyl groups selectively blocks excimer formation without severely compromising the TTA-UC efficiency.[2] The results demonstrate how the chemical structure can be modified to block unwanted intermolecular excited state relaxation pathways with minimal effect on the preferred ones. Furthermore, a method that relates upconversion efficiencies measured with steady state and pulsed excitation conditions will be described.[3]

11:05 - 11:35
Discussion
ORGELE 2.1
Chair: Eleni Stavrinidou
10:45 - 11:05
2.1-I1
Owens, Roisin
University of Cambridge - UK
Conducting polymer devices integrated with cell membranes
Owens, Roisin
University of Cambridge - UK, GB
Authors
Roisin Owens a
Affiliations
a, Department of Chemical Engineering and Biotechnology, University of Cambridge - UK, Cambridge CB2 3RA, UK, Cambridge, GB
Abstract

In vitro models of biological systems are essential for our understanding of biological systems. In many cases where animal models have failed to translate to useful data for human diseases, physiologically relevant in vitro models can bridge the gap. Many difficulties exist in interfacing complex, biologically relevant models with technology adapted for monitoring function. Polymeric electroactive materials and devices can bridge the gap between hard inflexible materials used for physical transducers and soft, compliant biological components. In this presentation, I will discuss our recent progress in adapting conducting polymer devices, both OECTs and electrodes, to integrate with a variety of cell membranes preserving native membrane function. Since the cell membrane is the gateway to the cell, this platform allows monitoring of pathogens such as virus that may enter the cell, or drugs or toxins that may interact with the membrane compromising normal function (e.g. toxins binding to ion channels in the membrane).  I this presentation I will describe the development of this platform and showcase how it may be used as a rapid and highly quantitative method for monitoring events occurring at the membrane in a robust and scalable manner without recourse to live cells.

 

11:05 - 11:25
2.1-I2
Meredith, Paul
SPECIFIC, College of Engineering Swansea University
Photophysical and Spin Properties of Melanins – Towards Bioelectronic Interfaces
Meredith, Paul
SPECIFIC, College of Engineering Swansea University, GB

Professor Meredith is professor of materials physics at the University of Queensland in Brisbane, Australia. He is currently an Australian Research Council Discovery Outstanding Research Award Fellow, co-director of the Centre for Organic Photonics and Electronics, and Director of the UQ Solar Initiative. His research involves the development of new sustainable high-tech materials for applications such as solar energy and bioelectronics, and he particularly specialises in the transport physics and electro-optics of disordered semiconductors. Professor Meredith is also the co-founder of several start-up companies including XeroCoat and Brisbane Materials Technology. He is the recipient of numerous awards including the Premier of Queensland’s Sustainability Award (2013) and is widely recognised for his contributions to innovation and the promotion of renewable energy in Australia. He serves on several advisory boards including the Premier of Queensland’s Climate Change Council, the Australian Solar Thermal Research Initiative Strategic Advisory Board, and the Australian Renewable Energy Agency Technical Advisory Board. He originally hails from South Wales, was educated at Swansea University and Heriot-Watt University, and was DTI Postdoctoral Fellow at the Cavendish Laboratory in Cambridge before spending 6 years as an industrial scientist with Proctor and Gamble.

Authors
Paul Meredith a
Affiliations
a, Department of Physics, Swansea University, UK, Singleton Park, University College, Sketty, Swansea SA2 8PR, Reino Unido, GB
Abstract

The melanins are a ubiquitous class of functional biomacromolecules found throughout nature in many roles including photo-protection, pigmentation and free radical scavenging [1]. Due to their hybrid ion-electron solid-state electrical conduction properties [2], synthetic melanins based upon poly-indolequinones have also emerged as a classic model for bioinspired optoelectronic materials in applications such as bioelectronics [3]. It has been known for several years that the solid-state DC and AC electrical conductivity in melanin thin films and pellets is strongly modulated by adsorbed water which takes part in a local radical reaction known as the comproportionation equilibrium [2]. The mechanism is likely generic in conducting biomaterials (and indeed certain synthetic polymers) which have ionisable groups with local pKas around neutrality [3]. In addition, melanins show pronounced solid-state photoconductivity which is also linked to this mechanism – and in particular to the conversion between two distinct spin populations, a carbon centred radical and photo-induced semiquinone [4].

In my talk I will describe the photo-physics and spin-related fundamentals of these processes and in particular discuss new work showing how the comproportionation equilibrium can be manipulated to modulate bulk electrical properties [5]. This leads to the exciting possibility of melanin-based bioelectronic devices such as a new all-solid-state transistor capable of high fidelity transduction between electrons and protons [6].

[1] P. Meredith and T. Sarna, Pigment Cell Research, 2006, 19, 572-594

[2] A. B. Mostert, B. J. Powell, F. L. Pratt, G. R. Hanson, T. Sarna, I. R. Gentle and P. Meredith, Proceedings of the National Academy USA, 2012, 109, 8943-8947

[3] P. Meredith, C. J. Bettinger, M. Irimia-Vladu, A. B. Mostert and P. E. Schwenn, Reports on Progress in Physics, 2013, 76, 034501

[4] A.B. Mostert, S.B. Rienecker, C. Noble, G.R. Hanson & P. Meredith, Science Advances, 2018, 4(3), eaaq1293

[5] A.B. Mostert et al., Journal of Materials Chemistry B, 2020, 35, 7825

[6] M. Sheliakina, A.B. Mostert & P. Meredith, Materials Horizons, 2018, 5, 256-263

11:25 - 11:45
2.1-I3
Tait, Claudia
University of Oxford
Characterisation of Unpaired Spins in Doped Organic Semiconductors by Electron Spin Resonance
Tait, Claudia
University of Oxford, GB
Authors
Claudia Tait a, b, Malavika Arvind c, Reckwitz Anna a, Neher Dieter c, Behrends Jan a
Affiliations
a, Department of Physics, Freie Universität Berlin
b, Department of Chemistry, University of Oxford, Oxford, UK
c, University of Potsdam, Soft Matter Physics, Karl-Liebknecht-Straße 24–25, Potsdam, 14476, DE
Abstract

Efficient molecular doping of organic semiconductors typically leads to the generation of paramagnetic species that can be studied by Electron Spin Resonance (ESR) spectroscopy to gain insights into the doping mechanism and the properties of the introduced spin centres. The ability of ESR to not only detect and quantify unpaired electron spins, but also obtain information on their molecular environment through measurement of interactions between unpaired electron spins as well as with magnetic nuclei in their environment has the potential to provide new insights through detailed characterisation of the doped material at the molecular level [1-3].

The p-type doping of the prototypical organic semiconductor poly(3-hexylthiophene) (P3HT) with two different molecular dopants, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and tris(pentafluorophenyl)borane (BCF) was investigated by continuous-wave and pulse ESR. Significant differences in the ESR spectral signatures obtained for P3HT doped with the two types of dopants pointed at fundamental differences in the molecular environment of the spin centres introduced on the P3HT backbone. Measurements at different microwave frequencies provided further insights into the nature of the detected paramagnetic species and allowed identification of contributions from the radical cation on P3HT and the F4TCNQ radical anion. The results suggested the presence of strong exchange interactions between the two types of spin-carrying species for this host-dopant combination.

The extent of spin delocalisation in the P3HT radical cation was quantified through the measurement of hyperfine interactions with the protons on the polymer backbone using the ENDOR (Electron Nuclear DOuble Resonance) technique. Comparison of results obtained for the two types of dopants and for the regioregular and regiorandom forms of P3HT showed different degrees of spin localisation depending on both the degree of order of the polymer chain and the type of dopant used.

11:45 - 12:05
Discussion
PEROPV 2.1
Chair not set
10:45 - 11:05
2.1-I1
Tan, Hairen
Nanjing University
High-Efficiency All-Perovskite Tandem Solar Cells
Tan, Hairen
Nanjing University, CN
Authors
Hairen Tan a
Affiliations
a, College of Engineering and Applied Sciences, Nanjing University
Abstract

Organic-inorganic halide perovskites have received widespread attention thanks to their strong light absorption, long carrier diffusion lengths, tunable bandgaps, and low temperature processing. Single-junction perovskite solar cells (PSCs) have achieved a boost of the power conversion efficiency (PCE) from 3.8% to 25.5% in just a decade. With the continuous growth of PCE in single-junction PSCs, exploiting of monolithic all-perovskite tandem solar cells is now an important strategy to go beyond the efficiency available in single-junction PSCs. In this tall, I will summarize our recent research progress in monolithic all-perovskite tandem solar cells from the perspectives of different structural units in the device: tunnel recombination junction, wide-bandgap top subcell, and narrow-bandgap bottom subcell. I will also present our strategies in fabricating all-perovskite triple-junction solar cells, in which the perovskite layers are all solution processed.

11:05 - 11:25
2.1-I2
You, Jingbi
Institute of Semiconductors, Chinese Academy of Sciences
Efficient perovskite solar cells with various bandgaps
You, Jingbi
Institute of Semiconductors, Chinese Academy of Sciences, CN
Authors
Jingbi You a
Affiliations
a, Institute of Semiconductors, Chinese Academy of Sciences, CN
Abstract

Perovskite solar cells with different bandgaps of absorber need to be studied for making efficient single or tandem solar cells. In this talk, I will talk about: 1) By charge transport layer and perovskite composition engineering, for the bandgap around 1.5 eV, we have achieved close to 25% efficiency with the FF close to 85%, 2) By surface passivation, we have pushed the PCE of inorganic perovskite CsPbI3 based solar cells to 20% efficiency, 3) According to the defect engineering, over 20% efficiency of the perovskite solar cells have been demonstrated for the perovskite bandgap around 1.35 eV.

11:25 - 11:45
2.1-I3
Hou, Yi
National University of Singapore
Textured perovskite/Si tandem solar cells: from the lab to fab?
Hou, Yi
National University of Singapore, SG
Authors
Yi Hou a, b
Affiliations
a, Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585 Singapore
b, Solar Energy Research Institute of Singapore (SERIS), National University of Singapore, 7 Engineering Drive 1, 117574, Singapore
Abstract

The development of perovskite/silicon tandem solar cells represents a promising strategy to enhance the performance of silicon-based photovoltaics beyond the single-junction Shockley-Queisser limit. Previous solution-processed perovskite/silicon tandems have relied on single-side textured silicon wafers. The flat-polished front side is compatible with perovskite solution processing; however, this configuration compromises optical light trapping. In this presentation I will discuss a perovskite/silicon tandem solar cell that unites high quality solution-processed perovskite solar cells with industry-relevant textured silicon. Optically, the fully textured bottom cells minimize reflection losses and provide efficient light trapping in the bottom cells, critical to satisfying the current-matching condition. Electronically, charge collection is improved in perovskites on textured Si substrates. The depletion region extends deep into the valleys formed by silicon pyramids in textured tandems. The self-limiting passivant that anchors on the rough wide-bandgap perovskite surfaces, stabilizing the bandgap. The advances reported herein show that it is possible – and powerful – to marry the industry-relevant textured silicon and perovskite technologies in tandems.

11:45 - 12:05
Discussion
RETCHEM 2.1
Chair not set
10:45 - 11:05
2.1-I1
Eddaoudi, Mohamed
King Abdullah University of Science and Technology (KAUST) - Saudi Arabia
Metal-Organic Frameworks (MOFs) as Prospect Adsorbents for Effective Carbon Capture.
Eddaoudi, Mohamed
King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, SA
Authors
Mohamed Eddaoudi a
Affiliations
a, King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal, SA
Abstract

We are at a critical juncture where both improvement of existing materials and new approaches to the design of novel materials are required to address the myriad technological challenges that face us, pertaining to energy an environmental sustainability.

The building-block approach, whereby at the design stage the desired properties and functionality can be introduced in preselected molecular building blocks (MBBs) prior to the assembly process, has emerged as a prominent pathway for the rational construction of functional solid- state materials. One class of inorganic-organic hybrid materials, metal-organic frameworks (MOFs), has burgeoned in recent past years as one of the most promising candidate materials for incorporating functionality by design. MOFs deservedly set at the forefront of contemporary materials research because their modular nature combines nanoscale porosity with enormous diversity of structure and property.

This inherent built-in information allows access to made-to-order porous materials, purporting great prospects to effectively enable the Carbon Removal and Reduction needs in the framework of Circular Carbon Economy (CCE). Markedly, KAUST MOF adsorbents are positioned to offer energy-efficient gas separations and effective carbon capture from diluted CO2 streams (e.g. NGCC) and eventually from the atmosphere, direct air capture (DAC).

11:05 - 11:25
2.1-I2
Li, Qiaowei
Fudan University
Structural Design of Multinary Metal-Organic Frameworks
Li, Qiaowei
Fudan University, CN
Authors
Qiaowei Li a
Affiliations
a, Department of Chemistry, Fudan University, Shanghai, China
Abstract

Metal-organic frameworks (MOFs) are usually constructed by one kind of metal and one kind of organic link. It remains a challenge to increase the number of components in one single framework, since the installation of multiple components in a well-ordered framework requires careful design of the lattice topology, judicious selection of building blocks, and precise control of the crystallization parameters[1].

In this talk, I will present several strategies to introduce multiple metals and linkers, in an ordered way, into one framework. We created ordered metal vacancies and linker vacancies in a cubic MOF by symmetry-guided removal of the metal ions and the linkers[2]. By filling the vacancies with new metals and new linkers, new single-crystalline MOFs with four components (two metals and two linkers) are introduced. Furthermore, multinary MOF structures were prepared by consolidating two metal ions (Cu and Zn) with distinct coordination preferences and geometries, and two or three different linkers, achieving quaternary and quinary MOFs[3]. We have further shown that the valence of the Cu ions can be switched between Cu(I) and Cu(II) without destroying the framework in these multinary MOFs[4]. The redox chemistry of these open metal sites was further evidenced by H2O2 decomposition, CO oxidation, and demonstrated for photodynamic therapy. In the end, I will show our progress in incorporating multiple linkers with variable lengths into one conservative matrix, pointing to a general method in creating linker variance along a specific direction in an ordered way.

11:25 - 11:45
2.1-I3
Banerjee, Rahul
Indian Institute of Science Education and Research Kolkata
Porous Framework Materials: Spheres, Films and Membranes
Banerjee, Rahul
Indian Institute of Science Education and Research Kolkata, IN
Authors
Rahul Banerjee a
Affiliations
a, IISER Kolkata
Abstract

Covalent Organic Frameworks (COFs) represent a new class of highly porous, crystalline polymers with uniformly arranged ordered pore channels.1 Even though COFs have been used for storage of a wide variety of molecular species like gases, nanoparticles, enzymes and drugs; the benefits of their ordered pore channels for molecular separation is hardly extracted. The key issue behind this problem is the difficulty of fabricating COF particles into a self-standing, stable membrane form. Apart from the processability, the other formidable obstacle that prevents utilization of COFs in real life applications are i) chemical stability, ii) difficult synthetic procedures, and iii) scalability. In this context, we have successfully overcome the chemical stability problem of COFs, by synthesizing β-ketoenamine based frameworks. Irreversible enol to keto tautomerism resulted in phenomenal stability within the frameworks.2 While processability, synthetic hurdles, and scalability of COFs still remain unexplored. In order to address these key issues, we have developed a very simple, scalable and novel methodology by which COFs can be synthesized by simple mixing and heating of the reactants. Using this method COF can be processed in to self-standing covalent organic framework membranes (COMs).3 The resultant COMs display higher porosity and crystallinity over their reported powder form. These self-standing COMs are flexible, continuous, devoid of any internal defects or cracks, show long-term durability. It retains structural integrity in water, organic solvents and even in mineral acid (3 N HCl). We have utilized these COMs for separation applications such as waste water treatment and recovery of valuable active pharmaceutical ingredients [APIs] from organic solvents.3 Our result highlight, that COMs could satisfactorily address world’s most challenging separation problems including waste water treatment, drug recovery from organic solvents in pharma industries.

11:45 - 12:05
Discussion
11:30 - 11:35
PEREMER Opening nanoGe
11:35 - 11:45
PEREMER Session Introduction 2.1
11:35 - 11:45
UPDOWN Session Introduction 2.2
PEREMER 2.1
Chair: Simon Kahmann
11:45 - 12:05
2.1-I1
Shao, Shuyan
2D/3D tin perovskites: crystallization mechanism and charge transport properties
Shao, Shuyan
Authors
Shuyan Shao a, b, Giuseppe Portale a, Maria Antonietta Loi a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
b, Current Address: Institute of Molecular Aggregation Science, Tianjin University, Weijin Street 92, 300072, Tianjin, China
Abstract

Tin based perovskites as an alternative to lead based counterparts have been drawing increasing research interest in various optoelectronic devices due to its excellent opto-electronic properties. However, pure 3D tin perovskites suffer from severe p-type doping due to formation of structural defects and oxidation by oxygen, which pose great challenges in obtaining highly efficient solar cells and working field effect transistors. We demonstrate that highly crystalline and oriented 3D tin perovskite forms in the presence of a tiny amount of 2D layered tin perovskite. We revealed the crystallization mechanism of the tin perovskites by systematically monitoring the dynamic crystallization process of the tin perovskites by in-situ and ex-situ grazing incidence wide angle x-ray scattering (GIWAXS) techniques. As a consequence of the enhanced lattice ordering, the hole carrier density of the 2D/3D tin perovskite mixtures is reduced by more than one order of magnitude as compared to pure 3D tin perovskite. This enables us to fabricate working field effect transistors (FET) and to investigate their charge transport properties. FET with 2D/3D tin perovskite as semiconducting channel exhibits good gate modulated p-type conduction behavior, a small threshold voltage (2.8 V), Ion/off in the order of 104, and hole mobility up to 0.21 m2/Vs. In contrast, the counterpart based on 3D tin perovskite failed to offer obvious gated modulated conduction behavior. 

12:05 - 12:25
2.1-I2
Egger, David
Technical University of Munich
Electronic Structure and Exciton Diffusion in 2D Halide Perovskites
Egger, David
Technical University of Munich, DE
Authors
David Egger a
Affiliations
a, Technical University of Munich, Physics Department, D-85748 Garching, DE
Abstract

The study of two-dimensional halide perovskites (2D HaPs) has received renewed great interest in the past few years in light of their potential use as materials in energy and optoelectronic devices. 2D HaPs also show various fascinating physical properties revolving around their electronic-structure and lattice-dynamical characteristics that are important for such technological applications. In this talk, I will present our recent theoretical findings on the electronic properties of 2D HaPs and discuss their role in various experimental settings. In particular, the combination of density functional theory calculations and high magnetic field spectroscopy will be used to demonstrate a broad tunability of the carrier effective mass in 2D HaPs, which is due to distortions imposed by the organic spacers and orbital hybridization effects by the metal cation.[1] Furthermore, the current limitations of standard semi-classical transport models to explain exciton diffusion around room temperature will be discussed on the basis of experimental results obtained from ultrafast emission microscopy for hBN-encapsulated 2D HaPs.[2]

12:25 - 12:45
2.1-I3
Nogueira, Ana Flavia
How in-situ experiments can help us to understand formation, stability and composition in two-dimensional perovskites
Nogueira, Ana Flavia
Authors
Ana Flavia Nogueira a
Affiliations
a, Laboratory of Nanotechnology and Solar Energy, Institute of Chemistry, University of Campinas – UNICAMP, P.O. Box 6154, Campinas, 13083-970, BR
Abstract

Metal halide perovskite solar cells have reached the recent efficiency breakthrough of 25.5%, higher than silicon polycrystalline photovoltaics. Such fantastic result was only possible due to a precise control and engineering of the morphology, interfaces and the use of multiple cations in perovskite A-site, as Rb, Cs, MA (methylamonnium) and FA (formamidinium). For tandem perovskite solar cells, a mixture of different anions, as Br and I is also desired to adjust the band gap. Such cocktail of different cations and anions influences the formation of intermediates, new phases, favours halide homogenization, etc; so that at the end, the efficiency of the device is closely related to not only the optical quality of the film (e.g. crystallinity), but morphology and composition.

In this presentation, we will summarize important results using in situ experiments to probe perovskite formation (2D and 3D), stability and composition. We employed time-resolved grazing incidence wide angle x-ray scattering (GIWAXS), small angle x-ray scattering (SAXS) and high-resolution XRD taken at the Brazilian Synchrotron National Laboratory and SSRL-Stanford.

In situ GIWAXS experiments allowed us to understand the influence of the relative humidity and time to drop the antisolvent during the preparation of perovskite films and get important information about final composition and morphology [1]. It is well known that a 2D layer on the top of a 3D bulk perovskite improves stability and performance. In situ GIWAXS revealed us that during thermal annealing the two-dimensional layer transforms itself into a disorder layer, improving hole transfer and stability [2]. This technique was also employed to identify the first intermediates formed during the degradation of different Cs and Br perovskite compositions under ambient conditions [3].

In situ SAXS is another powerful technique to follow the first stages of the two-dimensional perosvkite’s formation. Our results suggest that the formation of the individual slabs in BA2[FAPbI3]PbI4 is quite fast (within the first 10 s) and, then, these slabs self-assemble into bulk crystallites during the next 40 minutes [4].

 

 

12:45 - 13:05
Discussion
11:45 - 11:50
SELFNC Break
UPDOWN 2.2
Chair: Victor Gray
11:45 - 12:05
2.2-I1
Clark, Jenny
Department of Physics and Astronomy, University of Sheffield, UK
Triplet-pair states in (hetero)acenes and polyenes.
Clark, Jenny
Department of Physics and Astronomy, University of Sheffield, UK, GB
Authors
Jenny Clark a
Affiliations
a, Department of Physics and Astronomy, University of Sheffield, UK, Hounsfield Road, GB
Abstract

Incoherent up/down conversion can be achieved via triplet-triplet annihilation (TTA) up-conversion and its reverse, singlet exciton fission (SF) in molecular systems. However, fundamental understanding of these processes, and how they depend on material properties, is still lacking. In this talk I will describe recent work from my group focussing on the role and nature of triplet-pair states in SF and TTA in two classes of molecules: (hetero)acenes and polyene-like molecules such as carotenoids.

Our recent work on high-quality pentacene single crystals and anthradithiophene (diF-TES-ADT) thin films [1] demonstrates that distinct 1(TT) emission arises directly from bimolecular triplet–triplet annihilation. This suggests that a real, emissive triplet-pair state acts as an intermediate in both SF and TTA and that this is true for both endo- and exothermic singlet fission materials.

In polyenes, on the other hand, the lowest-lying intramolecular singlet state is already known to have significant 1(TT) character, but its role – and that of other triplet-pair states – in SF is far from clear. I will describe our recent work studying model protein systems [3] using transient and magnetic-field dependent spectroscopy to describe triplet-pair states in polyenes.

12:05 - 12:25
2.2-I2
Rao, Akshay
University of Cambridge - UK
Controlling Triplet Exciton Dynamics Using Hybrid Organic-Lanthanide Nanoparticle Systems
Rao, Akshay
University of Cambridge - UK, GB
Authors
Akshay Rao a
Affiliations
a, Optoelectronics Group, University of Cambridge, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Abstract

The generation, control and transfer of triplet excitons in molecular and hybrid systems is of great interest owing to their long lifetime and diffusion length in both solid-state and solution phase systems, and to their applications in light emission, optoelectronics, photon frequency conversion and photocatalysis. Molecular triplet excitons (bound electron–hole pairs) are ‘dark states’ because of the forbidden nature of the direct optical transition between the spin-zero ground state and the spin-one triplet levels8. Hence, triplet dynamics are conventionally controlled through heavy-metal-based spin–orbit coupling or tuning of the singlet–triplet energy splitting via molecular design. Both these methods place constraints on the range of properties that can be modified and the molecular structures that can be used.
In this talk I will introduce our recent work demonstratrating that it is possible to control triplet dynamics by coupling organic molecules to lanthanide-doped inorganic insulating nanoparticles. This allows the classically forbidden transitions from the ground-state singlet to excited-state triplets to gain oscillator strength, enabling triplets to be directly generated on molecules via photon absorption. Photogenerated singlet excitons can be converted to triplet excitons on sub-10-picosecond timescales with unity efficiency by intersystem crossing. Triplet exciton states of the molecules can undergo energy transfer to the lanthanide ions with unity efficiency, which allows us to achieve luminescent harvesting of the dark triplet excitons. Furthermore, we demonstrate that the triplet excitons generated in the lanthanide nanoparticle–molecule hybrid systems by near-infrared photoexcitation can undergo efficient upconversion via a lanthanide–triplet excitation fusion process: this process enables endothermic upconversion and allows efficient upconversion from near-infrared to visible frequencies in the solid state. These results provide a new way to control triplet excitons, which is essential for many fields of optoelectronic and biomedical research.

12:25 - 12:45
2.2-I3
Monguzzi, Angelo
University of Milano-Bicocca
Photon upconversion in multicomponent systems: Role of back energy transfer
Monguzzi, Angelo
University of Milano-Bicocca, IT
Authors
Angelo Monguzzi a
Affiliations
a, Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, via Roberto Cozzi 55, I-20125, Milano, Italy
Abstract

Photon upconversion based on sensitized triplet–triplet annihilation in bi-component systems is a multistep process that involves a triplet–triplet energy transfer (ET) from a donor to an acceptor moiety. This is aimed at sensitizing the population of annihilating optically dark triplets that generates the high energy photoluminescence. A large resonance between the involved triplets is usually recommended because it increases the energy gain between absorbed and emitted upconverted photons. However, it can also enable back-ET from acceptor to donor triplets, with potential detrimental consequences on the system performance. By analyzing a model system by means of time resolved and steady state photoluminescence spectroscopy, it is possible to develop a kinetic model that describes the iterative loop that transfers the triplet exciton between the donor and acceptor molecules. In such a way, it is possible to point out  the effect of the back-ET mechanisms on the upconversion process and evaluate potential detrimental effects, thus obtaining the guidelines for the optimization of the system composition required to maximize the upconversion quantum yield at low powers.

12:45 - 13:05
Discussion
11:50 - 12:00
SELFNC Session Introduction 2.2
SELFNC 2.2
Chair: Agustín Mihi
12:00 - 12:20
2.2-I1
Pastoriza-Santos, Isabel
Universidad de Vigo
Large-scale Plasmonic Superlaticces Fabrication through Microfluidics
Pastoriza-Santos, Isabel
Universidad de Vigo, ES

Ph. D. in Chemistry from the University of Vigo (Spain). She is currently Assoc. Prof at CINBIO-Department of Physical Chemistry. Since 2012, she is the leader of the Colloid Chemistry Group. Her current interest involves the synthesis, assembly and surface modification of nanoparticles with unique properties as well as development of (multi)functional nanostructured materials and tools with applicability in nanoplasmonics, (bio)sensing, catalysis and biomedicine.

Authors
Isabel Pastoriza-Santos a
Affiliations
a, CINBIO, Universidade de Vigo, Lagoas-Marcosende 36310 Vigo
Abstract

The assembly of Au nanoparticles into ordered three-dimensional supercrystals could pave the way towards a novel class of materials with improved properties for sensing, photocatalysis or light harvesting. The fabrication of high-quality superlatticess are strongly dependent on the monodistersity and surface chemistry of the nanoparticles used as building blocks as well as the assembly strategy. Herein I will show you the synthesis of highly monodispersed Au nanoctahedra as well as their assembly into uniform and large 3D supercrystals using microfluidics. The pervaporation-induced nanoparticles assembly was studied by a combination of X-ray scattering techniques with FIB-SEM tomography revealing single-domain supercrystals with long-range order and monoclinic C2/m symmetry.

Additionally, I will show that the integration of these supercrystals within microfluidic channels allows the fabrication of plasmonic microchips with outstanding SERS sensing capabilities even in biological medium.

12:20 - 12:40
2.2-I2
Acuna, Guillermo
University of Fribourg
DNA-mediated self-assembly of optical antennas for single molecule enhanced spectroscopies and nanophotonics
Acuna, Guillermo
University of Fribourg, CH
Authors
Guillermo Acuna a
Affiliations
a, Département de Physique - Photonic Nanosystems Université de Fribourg - Faculté des Sciences et de Médecine
Abstract

Over the last decade, the DNA origami technique [1] has consolidated into the state-of-the-art approach for the self-assembly of nanophotonic [2] structures since it provides unique control and versatility to organize different molecules and nanoparticles in well-defined geometric arrangements. In particular, this technique has proven extremely useful to fabricate nanophotonic devices with specific functionality by setting single-photon emitters, such as fluorescent molecules or quantum dots, and metallic nanoparticles in precise geometries with high positional and stoichiometric control.

In this contribution, we will first introduce this technique and discuss its strengths and limitations together with a comparison with state-of-the-art top down approaches. Then we will show how this technique can be applied to study light-matter interaction at the single molecule level for enhanced spectroscopies [3] (including fluorescence and Raman) and sensing with portable devices such as smartphones. We will also show how these antennas can be engineered to manipulate the fluorescence emission [4], including directivity and shifting the apparent fluorescence emission center [5].

12:40 - 13:00
2.2-I3
TREGUER-DELAPIERRE, Mona
ICMCB_CNRS, U.Bordeaux
SYMMETRIC PLASMONIC CLUSTERS FROM MULTI-STEP COLLOIDAL CHEMSITRY
TREGUER-DELAPIERRE, Mona
ICMCB_CNRS, U.Bordeaux, FR

Mona Tréguer-Delapierre received her PhD degree in physical chemistry from the University of Orsay, Paris Saclay. She has received an award from the Chancellerie des Universités de Paris for her PhD thesis. After a postdoctoral fellowship at the University of Notre Dame, Indiana (USA) with Dan Meisel, she joined the faculty in the Chemistry Department at the University of Bordeaux, in 2000. Her research is centered on the fabrication of nanomaterials for catalysis, biology and optics. She has published 100 papers in international journals including Nature, Nanoletters, ACS Nano, Phys.Rev.Lett., Adv.Mat, Material Horizons. She co-edited 3 book chapters and held 12 Patents. Recently, she was awarded as the H&M Zimmer Scholar from the University of Cincinnati (USA).

Authors
Mona TREGUER-DELAPIERRE a, Laurent LERMUSIAUX a, Alexandre BARON b, Philippe BAROIS b, Serge RAVAINE b, Etienne DUGUET a, Vinothan MANOHARAN c
Affiliations
a, ICMCB_CNRS, U.Bordeaux, 87 A. DR A. Schweitzer,, PESSAC, FR
b, CNRS, CRPP, F-33600 Pessac, FR
c, Department of Physics, Harvard University
Abstract

In this talk, we will describe a new approach to making plasmonic clusters with well-controlled resonances at optical wavelengths. These clusters consist of a small number of spherical plasmonic particles (up to 12). They are highly symmetric, subwavelength-scale clusters of metal and dielectric. They are of interest for metafluids, metasurfaces, isotropic optical materials with applications in imaging and optical communications. For such applications, the morphology must be precisely controlled: the optical response is sensitive to  the distances between metal satellites. To achieve this precision, we use a multi-step colloidal synthesis approach. Starting from highly monodisperse seeds, we grow symmetrical clusters of polymer spheres using seeded-growth polymerization. We then overgrow the silica and remove the polystyrene to create a dimpled template. Finally, we attach or grow a controlled number of gold or silver satellites to the template. The objects with a dodecahedral symmetry exhibit large electric and magnetic dipolar and quadrupolar responses. They display a strong forward scattering that may be used in various optical applications operating in visible light. More broadly, our approach shows how metamolecules can be produced in bulk by combining different, high-yield colloidal synthesis steps, analogous to how small molecules are produced by multi-step chemical reactions.

13:00 - 13:20
Discussion
12:05 - 13:30
Break
PEROPV 2.2
Chair not set
12:05 - 12:15
2.2-T1
Hu, Long
Macquarie University
Flexible and Efficient Perovskite Quantum Dot Solar Cells via Hybrid Interfacial Architecture
Hu, Long
Macquarie University, AU
Authors
Long Hu a, Shujuan Huang b
Affiliations
a, Macquarie University, AU
b, Macquarie University, AU
Abstract

 

Colloidal semiconducting quantum dots (QDs) are intensively researched due to outstanding optoelectronic properties and the tunable character based on size and surface related effects. All-inorganic CsPbI3 perovskite QDs have received substantial research interest for photovoltaic applications because of higher power conversion efficiency (PCE) compared to solar cells using other QD materials and the various exciting properties that perovskites have to offer. These QD devices also exhibit good mechanical stability amongst various thin-film photovoltaic technologies. A detailed morphological characterization reveals that the perovskite QD film can better retain structural integrity than large grain perovskite bulk thin film after external mechanical stress. We demonstrate higher mechanical endurance of QD films compared to bulk thin film and highlight the importance of further research on high-performance and flexible optoelectronic devices using nanoscale grains as an advantage. Specifically, we develop a hybrid interfacial architecture consisting of CsPbI3 QD/PCBM heterojunction, enabling an energy cascade for efficient charge transfer and mechanical adhesion. The champion CsPbI3 QD solar cell has a PCE of 15.1%, which is among the highest report to date. Building on this strategy, we further demonstrate a highest efficiency of 12.3% in flexible QD photovoltaics.

  

12:15 - 12:25
2.2-T2
Wang, Qiong
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany
Inorganic Perovskite Solar Cells: from The Bulk to The Interface
Wang, Qiong
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, DE
Authors
Qiong Wang a, Antonio Abate a
Affiliations
a, Helmholtz-Zentrum Berlin für Materialien und Energie, Young Investigator Group Active Materials and interfaces for stable perovskite solar cells, Kekulestraße, 5, Berlin, DE
Abstract

In this talk, we will first discuss the crystal structure stability challenges in inorganic perovskite, compared to that of organic-inorganic perovskite. In our work, we demonstrated that how the initial annealing temperature could play such a crucial role on the phase purity and crystal orientation in inorganic perovskite and therefore on the photovoltaic stability in the maximum power point measurement tracked for over 300 hours. Then from the bulk property of the inorganic perovskite, we moved to examine the interface property by applying two electron selective contacts. We found that a slower charge extraction was observed for the tin oxide that has a small conduction band minimum energy offset, which resulted in a poor fill factor in the devices. Prospects on future development and challenges in inorganic perovskite with pure iodide is discussed in the end.

12:25 - 12:35
2.2-T3
Simenas, Mantas
Vilnius University, Vilnius, Lithuania
Suppression of phase transitions and glass phase signatures in mixed cation halide perovskites
Simenas, Mantas
Vilnius University, Vilnius, Lithuania, LT
Authors
Mantas Simenas a, Sergejus Balciunas a, Jacob N. Wilson b, Sarunas Svirskas a, Martynas Kinka a, Vidmantas Kalendra a, Anna Gagor c, Daria Szewczyk c, Adam Sieradzki d, Miroslaw Maczka c, Aron Walsh b, e, Robertas Grigalaitis a, Juras Banys a
Affiliations
a, Faculty of Physics, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
b, Thomas Young Centre and Department ofMaterials, Imperial College London, SW7 2AZ London, UK
c, Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wroclaw, Poland
d, Department of Experimental Physics, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland
e, Department of Materials Science and Engineering, Yonsei University, 03722 Seoul, Korea
Abstract

Cation engineering provides a route to control the structure and properties of hybrid halide perovskites, which has resulted in the highest performance solar cells based on mixtures of Cs, methylammonium, and formamidinium. Here, we present a multi-technique experimental and theoretical study of structural phase transitions, structural phases and dipolar dynamics in the mixed hybrid perovskites including a novel methylammonium/dimethylammonium MA1-xDMAxPbBr3 (0 ≤ x ≤ 1) [1]. Our results demonstrate a significant suppression of the structural phase transitions, enhanced MA disorder and stabilization of the cubic phase even for a small level of mixing.We observe the disappearance of the structural phase transitions and indications of a glassy dipolar phase formation. We also reveal a significant tunability of the dielectric permittivity upon mixing of the molecular cations that arises from frustrated electric dipoles.

12:35 - 13:05
Discussion
13:05 - 14:00
PEREMER Break
13:05 - 15:15
PEROPV Break
13:05 - 13:10
UPDOWN Closing
13:10 - 14:10
UPDOWN Happpy Hour
13:20 - 15:00
SELFNC Break
13:30 - 13:40
ORGELE Session Introduction 2.2
ORGELE 2.2
Chair: James Ryan
13:40 - 14:00
2.2-I1
Nelson, Jenny
Imperial College London, United Kingdom
Understanding structure-property relationships in conjugated polymer electrodes for electrochemical energy storage
Nelson, Jenny
Imperial College London, United Kingdom, GB

Jenny Nelson is a Professor of Physics at Imperial College London, where she has researched novel varieties of material for use in solar cells since 1989. Her current research is focussed on understanding the properties of molecular semiconductor materials and their application to organic solar cells. This work combines fundamental electrical, spectroscopic and structural studies of molecular electronic materials with numerical modelling and device studies, with the aim of optimising the performance of plastic solar cells. She has published around 200 articles in peer reviewed journals, several book chapters and a book on the physics of solar cells.

Authors
Jenny Nelson a
Affiliations
a, Department of Physics, Imperial College London, London SW7 2AZ, UK
Abstract

Conjugated polymers with polar side chains are interesting candidates for electrodes in electrochemical devices because of their chemical tuneability, abundance, low cost, mechanical flexibility and the potential ease of both manufacture and recycling.  In particular, their electrochemical and redox properties can be tuned through independent choice of polymer backbone and side chain [1]. When applied as electrodes in electrochemical energy storage devices, conjugated polymer electrodes show excellent charging and discharging rates, high coulometric efficiency and compatibility with simple salt-water electrolytes [2]. However, their specific capacity is still low and their stability in ambient environments can be poor. In this work, we investigate the relationship between the functional properties of the electrodes, namely their specific capacity, rate capabilities, redox properties, electrochemical and mechanical stability, and the choice of side chains. We show that small changes of the side chain composition can significantly influence the degree of water uptake (and thereby the mechanical stability of the electrodes), the redox-stability of the materials in aqueous electrolytes, and the electrodes’ specific capacity. We use molecular dynamics and density functional theory calculations in order to understand how the chemical structure of the polymer controls the water and ion uptake in the conjugated polymer electrode, and how the structure and environment control the redox behaviour. Our work shows the value of chemical design strategies for developing high performance conjugated polymers for aqueous electrolytes.

14:00 - 14:20
2.2-I2
Fabiano, Simone
Linköping University
Toward dopant-free organic electronics
Fabiano, Simone
Linköping University, SE
Authors
Simone Fabiano a
Affiliations
a, Linköping University, Sweden, SE-581 83, Linköping, SE
Abstract

Chemical doping is crucial for the operation of organic (opto)electronic and electrochemical devices. This is typically achieved by adding dopant molecules to the polymer bulk, enabling high electrical conductivities. However, this process can result in poor stability and performance due to nonoptimal charge transfer and thin film morphologies. Besides, once the dopant molecules are incorporated, they tend to diffuse through the free volume between polymer chains or to escape during the heating steps, degrading both the electrical and mechanical properties of the semiconductor. In addition, the diffusion of dopant molecules could pose a risk when these materials are placed in contact with the human body like e.g., in the case of wearable sensors. Thus, molecular doping of organic semiconductors significantly limits their implementation into novel opto-/bioelectronics applications. In this presentation, we will report on our recent efforts to develop stable and highly conductive polymer blends based on mutual electrical doping. First, we will discuss the case of non-conjugated polymeric dopants and then move toward a new generation of conjugated polymer-donor/polymer-acceptor blends based on the effect of ground-state electron transfer in all-polymer heterojunctions. These molecular dopant-free systems hold promise for the development of next-generation opto-/bioelectronics devices, in particular targeting novel functionality, efficiency and power performance.

14:20 - 14:40
2.2-I3
Ludwigs, Sabine
University of Stuttgart
Bioinspired Mixed Conducting Polymer Films
Ludwigs, Sabine
University of Stuttgart, DE
Authors
Sabine Ludwigs a
Affiliations
a, University of Stuttgart, DE
Abstract

The beauty and multifunctionality of nature has been a constant inspiration for materials scientists to mimic functionalities and hierarchical structures in man-made materials. Both, color and motion in plants are examples which can be - to some extent - replicated by stimuli-responsive polymers and materials thereof. The field of expertise of my group are conducting polymers which are used in a number of polymer electronics devices, but also in electrochemical applications where electronic and ionic charge transport are intimately linked with each other.1

Among various self-synthesized materials we study the commercially available blend poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Apart from its use as “synthetic metal” as transparent flexible electrode, the material is a mixed conductor and shows ionic conductivity which is strongly affected by humidity.2 The humidity dependence of the PSS polyelectrolyte phase together with the electroactive nature of the PEDOT can be used to create multifunctional and multiresponsive materials. A recent example from my group is the preparation of “intelligent” humidity-triggered bilayer actuators whose bending behavior (curvature) can be nicely explained by the humidity-dependent mechanical behavior of the constituents.3

 


 

14:40 - 15:00
Discussion
PEREMER 2.2
Chair: David Egger
14:00 - 14:10
2.2-T1
Lédée, Ferdinand
CNRS, University Paris-Saclay
DISCUSSING OPTICAL PROCESSES IN 2D LAYERED PEROVSKITES INCORPORATING PHOTO-ACTIVE SPACERS : TETRAZINE AS IDEAL TEST-BED FOR CHARGE AND ENERGY TRANSFER PROCESSES.
Lédée, Ferdinand
CNRS, University Paris-Saclay, FR
Authors
Ferdinand Lédée a, b, Pierre Audebert b, Gaëlle Trippé-Allard a, Laurent Galmiche b, Damien Garrot c, Jérôme Marrot d, Jean-Sébastien Lauret a, Emmanuelle Deleporte a, Claudine Katan e, Jacky Even f, Claudio Quarti g
Affiliations
a, CNRS, University Paris-Saclay, Boulevard Thomas Gobert, 10, Palaiseau, FR
b, PPSM, ENS Paris-Saclay, CNRS, Université Paris-Saclay, France
c, Groupe d’Etude de la Matière Condensée, Université de Versailles Saint Quentin En Yvelines, Université Paris-Saclay, France, Avenue des États Unis, 45, Versailles, FR
d, Université Paris-Saclay, UVSQ, CNRS, Institut Lavoisier de Versailles, France, FR
e, Univ Rennes, ENSCR, INSA Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F 35000 Rennes, France
f, Université Européenne de Bretagne, INSA, FOTON, UMR 6082, France, FR
g, University of Mons, Laboratory for Chemistry of Novel Materials, B-7000 Mons, Belgium
Abstract

Hybrid perovskites are on the verge of revolutionizing the field of opto-electronics. While 3D perovskites such as CH3NH3PbI3 were made famous by their impressive performances in solar cells, 2D layered perovskites have attracted renewed interest in the past few years. This class of perovskites covering the compounds with stoichiometry (R-NH3)2BX4 (B = Pb2+ , Sn2+ ; X = I- , Br- , Cl- and R = C6H5C2H4 , C4H9) have shown recently remarkable potentiality in a broad range of applications.1–3 Layered structure inherently relaxes the size requirements for the organic component, as expressed in the 3D case by the Goldschmidt tolerance factor, hence widely extending the number of potential organic compounds to be incorporated in these hybrid structures. To date, most reports on 2D layered perovskites use aliphatic or mono aromatic compounds characterized by large HOMO-LUMO gap (5 – 6 eV). It is now well known that these compounds form type-I multiple quantum well-like structures, characterized by important quantum and dielectric confinement effects in the inorganic sheets, the organic sheets acting as insulating barriers.4 To go further, including optically active chromophores as organic spacers represents an original and effective strategy to tune the optoelectronic properties of 2D layered perovskites.5 In particular, ways for charge and energy transfer phenomena at the inorganic/organic interface, such as exciton separation or organic–mediated charge transport, will be opened, which are potentially useful for optoelectronic applications.

In this work, we took advantage of the compositional flexibility of 2D layered perovskites to introduce optically active s-tetrazine (R-C2N4-R) in the perovskite structure. These small luminophores possess unique, low energy n->π* visible transition as well as a higher energy π->π* UV transition displaying quasi-perfect optical matching with the exciton resonance of the lead-chloride and mixed chloride/bromide perovskite frames. Here, we successfully synthesized 2D perovskites containing 100% of the theoretical content of the photoactive s-tetrazine organic moieties. We further performed extensive optical characterization supported by computational studies, in order to gain a complete picture of all potential charge and energy transfer processes ongoing in this complex perovskite-luminophore system. More specifically, both excited states as well as band alignment were studied to rationalize the complete quenching of the perovskites light-emission. We conclude that several decay channels may coexist between the s-tetrazine and the perovskite frame, and highlight the necessity of depicting these materials at the level of both excitonic and monoelectronic states.

14:10 - 14:20
2.2-T2
Magdaleno, Alvaro J
Condensed Matter Physics Center (IFIMAC), Autonomous University of Madrid
Efficient Interlayer Exciton Transport in Two-Dimensional Metal-Halide Perovskites
Magdaleno, Alvaro J
Condensed Matter Physics Center (IFIMAC), Autonomous University of Madrid, ES
Authors
Alvaro J Magdaleno a, b, Michael Seitz a, b, Michel Frising a, b, Ana Herranz de la Cruz a, b, Antonio I Fernández-Domínguez a, c, Ferry Prins a, b
Affiliations
a, Condensed Matter Physics Center (IFIMAC), Autonomous University of Madrid, Madrid, ES
b, Department of Condensed Matter Physics, Autonomous University of Madrid
c, Department of Theoretical Condensed Matter Physics, Autonomous University of Madrid, Madrid, ES
Abstract

Two-dimensional (2D) metal-halide perovskites have emerged as a more robust alternative to their three-dimensional counterparts. Due to quantum and dielectric confinement effects, excitons dominate the energy transport characteristics in thinnest members of the 2D perovskites family. Recently we have reported on the in-plane exciton diffusion using transient photoluminescence microscopy, where high diffusivities were found (0.2 cm2/s for PEA2PbI4).1 Using the same technique, here, we will show that this material exhibits remarkably efficient out-of-plane exciton transport (0.06 cm2/s) as well. This out-of-plane diffusivity translates to a diffusion length of exceeds 100 nm, making it relevant to device design. Moreover, our result show that the individual energy transfer steps that underly the out-of-plane transport occur on a sub-ps timescale. Such ultrafast timescales are over two orders of magnitude faster than predictions using Förster theory. We will discuss the shortcomings of Förster theory for the case of excitons in the layered perovskites. Most importantly, our results show that the excitonic energy transport is considerably less anisotropic than charge-carrier transport for 2D perovskites.2

14:20 - 14:30
2.2-T3
Marchal, Nadège
Università degli Studi di Perugia - CNR-ISTM
Theoretical Analysis of <110> and <100> Low-dimensional Lead Halide Perovskites with a Promising Organic-Inorganic Level Alignment
Marchal, Nadège
Università degli Studi di Perugia - CNR-ISTM, IT
Authors
Nadège Marchal a, b, Edoardo Mosconi a, Gonzalo García-Espejo e, Claudio Quarti b, David Beljonne b, Filippo De Angelis a, c, d
Affiliations
a, Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-SCITEC, Italy, IT
b, University of Mons, Laboratory for Chemistry of Novel Materials, B-7000 Mons, Belgium
c, CompuNet, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
d, Department of Chemistry, Biology and Biotechnology, University of Perugia, via Elce di Sotto 8, I-06123 Perugia, Italy
e, Dipartimento di Scienza e Alta Tecnologia & To.Sca.Lab., Università dell'Insubria, via Valleggio 11, 22100 Como, Italy
Abstract

Currently, low-dimensional lead halide hybrid perovskites are in the spotlight because of their improved stability and their interesting chemical flexibility compared to their 3D counterparts. These improvements come however at the expense of their electronic properties. Indeed, commonly employed organic spacers, mainly consisting in alkyl- or phenyl-derivatives, do not have common Bloch states with the inorganic frame. Then, these cations act as barriers for the charge and energy diffusion along the direction of the plane stacking, which results in poor charge collection in technologic devices, as solar cells1. Then, one of the current approaches to overcome this drawback is to design novel functionalized organic cations and innovative hybrid interfaces, whose electronic level could sustain more effective charge/energy transport processes, not only within the inorganic sheets but also along the normal direction2,3,4 .

Aiming to provide guidelines for the development of novel and more performant layered perovskite materials, we perform here cutting-edge electronic structure calculations, both for the organic spacer in gas phase and when embedded into the crystal lattice. Based on an in-depth analysis of the results obtained from Density Functional Theory calculations, we screen new electronically active cations. In addition, we assess the role of the organic/inorganic interfaces, by considering not only commonly used <100> terminated layered inorganic frames but also less investigated <110> ones5,6. We show that, thanks to its zig-zag conformation, <110> surface termination offers extended possibilities to enhance the electronic interaction, between the organic and the inorganic components. In particular, we find that spacers incorporating only one aromatic ring show non-negligible hybridization with lead-iodide <110> terminated sheets, while this is not the case for <100> terminated sheets7. This interaction mainly involves the highest occupied molecular orbital of the organic spacer and the valence band maximum of the inorganic frame, hence mainly affecting the transfer processes related to the photogenerated holes. A significant interplay of A-cation size, electronic structure and steric constraints is revealed, suggesting intriguing means of further tuning the 2D perovskite electronic structure towards achieving stable and efficient solar cell devices.

14:30 - 14:40
2.2-T4
Tekelenburg, Eelco
University of Groningen, The Netherlands
The Impact of Cation Fluorination on the Structure and Photophysics of Layered Perovskites
Tekelenburg, Eelco
University of Groningen, The Netherlands, NL
Authors
Eelco Tekelenburg a, Simon Kahmann a, b, Machteld Kamminga a, c, Graeme Blake a, Maria Loi a
Affiliations
a, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands, Nijenborgh 4, Groningen, NL
b, Cavendish Laboratory, Department of Physics, University of Cambridge, UK, JJ Thomson Avenue, Cambridge, GB
c, Niels Bohr Institute, University of Copenhagen
Abstract

Layered perovskites are a promising class of materials for solar cells and light-emitting devices. These materials consist of inorganic sheets sandwiched between organic cations, which result in ideal 2D structures with concomitant rich excitonic photophysics. Although layered perovskites display a well-documented improved stability towards heat and moisture compared to 3D perovskites, their structure and photophysics received far less attention. In this study, we elucidate the structure and its photophysics of the commonly employed phenethylammonium lead iodide (PEA) and its fluorinated derivative (3-FPEA). The bulkier 3-FPEA increases the distortion of the inorganic sheets, hereby shifting the absorption and emission peak to higher energy. Low-temperature photoluminescence spectroscopy reveals complex emission spectra. 3-FPEA shows hot-exciton resonances at high energy separated by 12 to 15 meV, in contrast to the 40 to 46 meV in PEA. High-resolution spectra show that the emission at lower energy consists of a substructure, previously thought to be a single line. We propose that the low-energy emission originates from excitons bound to defects by analysing a series of power-dependent, temperature-dependent, and time-resolved photoluminescence spectra. This work serves to further the understanding of the fundamental properties of layered perovskites.

14:40 - 15:10
Discussion
15:00 - 15:05
ORGELE Closing
15:00 - 15:05
SELFNC Opening nanoGe
15:05 - 17:00
ORGELE Happy Hour
15:05 - 15:15
SELFNC Session Introduction 2.3
15:10 - 15:20
PEREMER Session Introduction 2.3
15:15 - 15:20
RETCHEM Opening nanoGe
SELFNC Session 2.3
Chair: Elena V. Shevchenko
15:15 - 15:35
2.3-I1
Gang, Oleg
Columbia University and Brookhaven National Laboratory
Engineering and assembling targeted 3D nanomaterials through DNA programmability
Gang, Oleg
Columbia University and Brookhaven National Laboratory, US
Authors
Oleg Gang a
Affiliations
a, Columbia University and Brookhaven National Laboratory, US
Abstract

The ability to organize functional inorganic and bioderived nano-components into desired 3D architectures with targeted properties can enable a broad range of nanotechnological applications, from designed biomaterial to optical and information processing systems. However, we are currently lacking an adaptable and broadly applicable methodology for the bottom-up 3D nanofabrication of the prescribed nano-structures. I will discuss our efforts in establishing a versatile platform for the formation of targeted 3D architectures from inorganic and biomolecular nano-components using a DNA-programmable assembly strategy. The recent advances in building periodic and hierarchical organizations from inorganic nanoparticles, proteins and enzymes using DNA-based methods will be presented. I will demonstrate the use of these assembly approaches for creating complex 3D inorganic nanomaterials and for a fabrication of nanosystems with novel nano-optical, electrical and biochemical functions.

15:35 - 15:55
2.3-I2
Glotzer, Sharon
University of Michigan
From self assembly to colloidal robots
Glotzer, Sharon
University of Michigan, US
Authors
Sharon Glotzer a
Affiliations
a, Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
Abstract
15:55 - 16:15
2.3-I3
Braun, Paul
University of Illinois at Urbana-Champaign
Additive assembly of ultra-high refractive index contrast gradient index lenses and 3D waveguides in nanoporous materials
Braun, Paul
University of Illinois at Urbana-Champaign, US

Prof. Paul V. Braun is the Director of the Materials Research Laboratory, the Grainger Distinguished Chair in Engineering, and Professor of Materials Science and Engineering. He also has a co-appointment as a Professor in Chemistry and is affiliated with the Department of Mechanical Sciences and Engineering and the Beckman Institute for Advanced Science and Technology. Prof. Braun has co-authored a book, about 300 peer-reviewed publications, been awarded multiple patents, and has co-founded three companies. He is the recipient of the Illinois MatSE Young Alumnus Award (2011), the Friedrich Wilhelm Bessel Research Award of the Alexander von Humboldt Foundation (2010), the Stanley H. Pierce Faculty Award (2010), the 2002 Robert Lansing Hardy Award from TMS, a Beckman Young Investigator Award (2001), a 3M Nontenured Faculty Award (2001), the Xerox Award for Faculty Research (2004, 2009), and multiple teaching awards. He is a Fellow of the Materials Research Society and AAAS.

Authors
Paul Braun a
Affiliations
a, University of Illinois at Urbana-Champaign, South Mathews Avenue, 600, Urbana, US
Abstract

Here, we present Subsurface Controllable Refractive Index via Beam Exposure (SCRIBE), a lithographic approach that enables the tuning of the refractive index inside nanostructured porous solids over a range of greater than 0.3 [1]. The basis of SCRIBE is multiphoton polymerization inside monomer-filled nanoporous silicon and silica scaffolds. Adjusting the laser exposure during printing enables 3D submicron control of the polymer infilling and thus the refractive index and chromatic dispersion. Combining SCRIBE’s unprecedented index range and 3D writing accuracy has realized the world’s smallest (15 µm diameter) spherical Luneburg lens operating at visible wavelengths. SCRIBE’s ability to tune the chromatic dispersion alongside the refractive index was leveraged to render achromatic doublets in a single printing step, eliminating the need for multiple photoresins and writing sequences. SCRIBE also has the potential to form multicomponent optics by cascading optical elements within a scaffold. As a demonstration, stacked focusing structures that generate photonic nanojets were fabricated inside porous silicon. Finally, an all-pass ring resonator was coupled to a subsurface 3D waveguide. The measured quality factor of 4600 at 1550 nm suggests the possibility of compact photonic systems with optical interconnects that traverse multiple planes. SCRIBE is uniquely suited for constructing such photonic integrated circuits due to its ability to integrate multiple optical components, including lenses and waveguides, without additional printed supports and compatible with almost any nanostructured host as long as the host does not strongly absorb the writing laser (~800 nm) and the structure can be filled with monomer.

16:15 - 16:35
Discussion
PEREMER 2.3
Chair: Giulia Grancini
15:20 - 15:40
2.3-I1
Mitzi, David
Duke University
2D Hybrid Perovskites: Highly Diverse and Tunable Semiconductors
Mitzi, David
Duke University, US

David Mitzi received a B.S.E. in Electrical Engineering from Princeton University in 1985 and a Ph.D. in Applied Physics from Stanford University in 1990. In 1990, he joined the IBM T. J. Watson Research Center and initiated a program examining structure-property relationships, low-cost thin-film deposition techniques and device applications for a variety of electronic materials (e.g., oxides, halides, chalcogenides, organic-inorganic hybrids). Between 2009 and 2014 he managed the Photovoltaic Science and Technology department at IBM, with a focus on developing solution-processed high-performance inorganic semiconductors for thin-film photovoltaic (PV) devices. In July 2015, Dr. Mitzi moved to the Department of Mechanical Engineering and Materials Science at Duke University as a professor. He holds a number of patents and has authored or coauthored more than 180 papers and book chapters.

Authors
David Mitzi a
Affiliations
a, Duke University, PO Box 90281, Durham, 27708, US
Abstract

Hybrid semiconductors offer an unprecedented degree of tunability through mixing and matching of diverse inorganic and organic functionalities [1]. Two-dimensional (2D) perovskites (i.e., conceptionally derived from the 3D parent structure by taking 2D cuts and stacking these up in alternation with organic cations) represent particularly interesting examples, due to the extraordinary flexibility of organic chemistry for tailoring molecular components. In these systems, the interactions among organic cations and at organic-inorganic interfaces (mediated by hydrogen bonding and steric interactions) play an especially important role in determining emergent properties. As one example, selection of suitable chiral organic cations may lead to a transfer of chirality to and an associated breaking of symmetry within the inorganic layers, which in turn can provide a large Rashba-Dresselhaus splitting of the conduction band and associated control over spin texture [2]. Alternatively, the organic cation may be used to lower the melting temperature of hybrid perovskites by >100°C for a given inorganic framework [3], enabling facile film melt-processing and the design of hybrid phase-change materials that exhibit convenient glass-crystalline switching and associated modulation in optoelectronic properties [4]. The above examples of tunability point to new opportunities for fundamental science and prospective device applications.   

15:40 - 16:00
2.3-I2
Solis-Ibarra, Diego
Instituto de Energías Renovables - Universidad Nacional Autónoma de México
When 2D Perovskites Meet Conducting Polymers
Solis-Ibarra, Diego
Instituto de Energías Renovables - Universidad Nacional Autónoma de México, MX
Authors
Diego Solis-Ibarra a
Affiliations
a, National Autonomous University of Mexico, Circuito Exterior S/N Circuito de la, Investigación Científica, C.U., CDMX, MX
Abstract

Two‐dimensional (2D) organic-inorganic perovskites have recently become an attractive alternative to three‐dimensional (3D) perovskites due to their chemical and structural diversity and improved stability and stability. Despite their advantages, the organic cations' insulating nature and diminished light absorption limit some of their application. 

In this talk, we will show how the incorporation of conjugated diynes in 2D perovskites and subsequent thermal treatment results in the topochemical formation of 2D perovskites that incorporate polydiacetylenes in their structure. The incorporation of polydiacetylenes results in drastic improvements in these materials' properties, such as improved stability, light absorption, electrical conductivity, and hydrophobicity. Finally, we will discuss our recent findings on the area as well as potential avenues for improvement.

16:00 - 16:20
2.3-I3
Huang, Libai
Purdue University
Long-Range Exciton Transport and Slow Annihilation in Two-Dimensional Hybrid Perovskites
Huang, Libai
Purdue University, US
Authors
Libai Huang a
Affiliations
a, Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
Abstract

Two-dimensional hybrid organic-inorganic perovskites with strongly bound excitons and tunable structures are desirable for optoelectronic applications. Exciton transport and annihilation are two key processes in determining device efficiencies; however, a thorough understanding of these processes is hindered by that annihilation rates are often convoluted with exciton diffusion constants. Here we employ transient absorption microscopy to disentangle quantum-well-thickness-dependent exciton diffusion and annihilation in two-dimensional perovskites, unraveling the key role of electron-hole interactions and dielectric screening. The exciton diffusion constant is found to increase with quantum-well thickness, ranging from 0.06 ± 0.03 to 0.34 ± 0.03 cm2s-1, which leads to long-range exciton diffusion over hundreds of nanometers. The exciton annihilation rates are more than one order of magnitude lower than those found in the monolayers of transition metal dichalcogenides. The combination of long-range exciton transport and slow annihilation highlights the unique attributes of two-dimensional perovskites as an exciting class of optoelectronic materials.

16:20 - 16:40
Discussion
15:20 - 15:30
RETCHEM Session Introduction 2.1
15:30 - 15:40
PEROPV Session Introduction 2.3
RETCHEM 2.1
Chair not set
15:30 - 15:50
2.1-I1
Lotsch, Bettina
Max Planck Institute for Solid State Research, Stuttgart, Germany
Porous Frameworks for Solar Energy Conversion: Design, Disorder, and Defects
Lotsch, Bettina
Max Planck Institute for Solid State Research, Stuttgart, Germany, DE

Bettina Lotsch is the Director of the Nanochemistry Department at the Max Planck Institute for Solid State Research (MPI-FKF) in Stuttgart, Germany. She studied Chemistry at the Ludwig-Maximilians-Universität München (LMU) and the University of Oxford and received her PhD from LMU Munich in 2006. After a postdoctoral stay at the University of Toronto she became professor at LMU Munich in 2009 and was appointed Director at MPI-FKF in 2017. Bettina also holds honorary professorships at LMU Munich and the University of Stuttgart, and is PI of the Munich-based Cluster of Excellence e-conversion.

Bettina’s research explores the rational synthesis of new materials by combining the tools of molecular, solid-state and nanochemistry. Current research interests include molecular frameworks for solar energy conversion and storage, solid electrolytes for all-solid-state batteries, and “smart” photonic crystals for optical sensing.

Bettina was awarded an ERC Starting Grant (2014) and has been elected a Fellow of the Royal Society of Chemistry in 2014. Her work has been recognized by a number of awards, including the EU-40 Materials Prize 2017 of the European Materials Research Society.

Authors
Bettina Lotsch b
Affiliations
a, Max Planck Institute for Solid State Research, Stuttgart, Germany, DE
b, Ludwig- Maximilians-Universität München (LMU), Königinstraße 10, München, DE
Abstract

From a design perspective, metal and covalent organic frameworks (MOFs and COFs) are highly attractive materials for energy conversion and storage, as they are widely tunable at the molecular level while being robust and structurally precise. As a new generation of metal-free semiconductors, 2D COFs have recently put a new spin on the development of “all-single-site” heterogenous photocatalysts owing to their tunable optoelectronic properties, combined with ordered porosity.

While the development of molecular frameworks with competitive photocatalytic efficiencies is rapid, our understanding of what drives photocatalytic activity and how to translate this knowledge into rational catalyst design is still limited. Since catalysis occurs at the local level (the “active site”) and is often driven by defects, insight into the local structure and control of disorder and defects is mandatory.

In this talk I will present our recent progress towards the design of COF photocatalysts for the hydrogen evolution reaction with a particular focus on structure—property—activity relationships. I will discuss the structural (local and long range), optoelectronic and catalytic boundary conditions guiding our design of all-single-site COF photocatalysts and highlight the importance of real structure effects and defects in COFs and MOFs as a future design principle to create precisely tailored porous frameworks for catalysis and beyond.

15:50 - 16:10
2.1-I2
Mirica, Katherine
Dartmouth College
Energy-Efficient MOF-Based Electronic Textiles for Simultaneous Detection, Filtration, and Decontamination of Toxic Gases
Mirica, Katherine
Dartmouth College, DE

Katherine was born and raised in Eastern Ukraine, and moved with her family to the state of Rhode Island during her freshman year in high school.  She attended Boston College, where she developed a passion for Materials Chemistry, working in the laboratory of Lawrence T. Scott.  She graduated with high honors in 2004, and later that year moved across the river to pursue graduate studies at Harvard University.  In 2011, Katherine earned her Ph.D. in Chemistry from Harvard University under the guidance of George M. Whitesides. Her doctoral dissertation focused on the development and characterization of a simple and portable method that used magnetic levitation for density-based chemical analysis. She also contributed to several other research efforts in the areas of paper-based diagnostics and protein biophysics.  Katherine then joined the laboratory of Timothy M. Swager at the Massachusetts Institute of Technology as an NIH postdoctoral fellow to pursue the development of portable electronic carbon-based chemical sensors for the detection of hazardous gases and vapors.  At MIT, she developed a solvent-free approach, operationally analogous to drawing with pencil on paper, for the fabrication of sensitive and selective sensors from carbon nanomaterials. Katherine began her independent scientific career as an Assistant Professor in the Department of Chemistry at Dartmouth College in July 2015. She is a recipient of the Army Research Office Young Investigator Award (2017), Sloan Research Fellowship (2018), 3M Non-Tenured Faculty Award (2018-2019), and Cottrell Scholars Award (2019).

Authors
Katherine Mirica a
Affiliations
a, Department of Chemistry, Dartmouth College, Hanover, DE
Abstract

Wearable electronics have the potential to advance personalized health care, alleviate disability, enhance communication, and improve homeland security. Development of multifunctional electronic textiles (e-textiles) with the capacity to interact with the local environment is a promising strategy for achieving electronic transduction of physical and chemical information. This paper describes a simple and rapid approach for fabricating multifunctional e-textiles by integrating and patterning conductive two-dimensional (2D) metal−organic frameworks (MOFs) into fabrics through direct solution-phase self-assembly from simple molecular building blocks. These e-textiles display reliable conductivity, enhanced porosity, flexibility, exceptional stability to washing and ability to transduce chemical stimuli in low-power, energy efficient electronic sensors. The functional utility of these integrated systems is demonstrated in the context of chemiresistive gas sensing, uptake, and decontamination of toxic gases.

16:10 - 16:30
2.1-I3
Farha, Omar
Smart and Programmable Sponges for protection
Farha, Omar
Authors
Omar Farha a
Affiliations
a, Department of Chemistry, Northwestern University, Evanston, IL, 60208, USA
Abstract

This talk will focus on metal-organic frameworks (MOFs) from basic research to implementation and commercialization. MOFs are a class of porous, crystalline materials composed of metal-based nodes and organic ligands that self-assemble into multi-dimensional lattices. In contrast to conventional porous materials such as zeolites and activated carbon, an abundantly diverse set of molecular building blocks allows for the realization of MOFs with a broad range of properties. We have developed an extensive understanding of how the physical architecture and chemical properties of MOFs affect material performance in applications such as catalytic activity for the degradation of chemical warfare agents and simulants. 

16:30 - 16:50
Discussion
PEROPV 2.3
Chair not set
15:40 - 16:00
2.3-I1
Nazeeruddin, Mohammad Khaja
Ecole Polytechnique Federale de Lausanne (EPFL)
Perovskites Solar Cells: A New Paradigm in the Energy Sector
Nazeeruddin, Mohammad Khaja
Ecole Polytechnique Federale de Lausanne (EPFL), CH

Dr. Md. K. Nazeeruddin received M.Sc. and Ph. D. in inorganic chemistry from Osmania University, Hyderabad, India. His current research focuses on Dye-sensitized solar cells, Hydrogen production, Light-emitting diodes and Chemical sensors. He has published more than 400 peer-reviewed papers, nine book chapters, and inventor of 49 patents. The high impact of his work has been recognized with invitations to speak at over 100 international conferences. He appeared in the ISI listing of most cited chemists, and has more than 10000 citations with an h-index of 93. He is directing, and managing several industrial, national, and European Union projects on Hydrogen energy, Photovoltaics (DSC), and Organic Light Emitting Diodes. He was awarded EPFL Excellence prize in 1998 and 2006, Brazilian FAPESP Fellowship in 1999, Japanese Government Science & Technology Agency Fellowship, in 1998, Government of India National Fellowship in 1987-1988. Recently he has been appointed as World Class University (WCU) professor for the period of March 1, 2009 ~ December 31, 2012 by the Korea University, Jochiwon, Korea.

Authors
Mohammad Khaja Nazeeruddin a, Bin Ding a, Ding Yong a, b, Hiroyuki Kanda a, Zhang Yi a, Paul J. Dyson a
Affiliations
a, The Group for Molecular Engineering of Functional Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1951 Sion, Switzerland.
b, North China Electric Power University, State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, No.2 Beinong Road, Changping District, Beijing, 102206, Country: China
Abstract

Perovskite solar cells (PSC) are a new paradigm in renewable energy because of their high efficiency reaching over 25%. The perovskite solar cells' high efficiency is due to their excellent optoelectronic properties, which were optimized by various cations and anions with different ratios. Another advantage of perovskite solar cells is their simple fabrication through solution-processing methods, either in n-i-p or p-i-n configurations. However, the PSCs' long-term stability is still a significant concern and is the bottleneck to commercialization. We have developed strategies to enhance the stability by using functionalized ionic liquids as additives and interface engineering by hydrophobic 2-Dimensional perovskite materials, preventing ion migration and protecting the perovskite absorber. The long-term stability of unencapsulated devices under one sun illumination retains>95% of their original efficiencies after 1000 h aging. In this talk, we present layer by layer deposition of 3-Dimensional and 2-Dimensional perovskites and compositionally engineered perovskite with polymerizable novel ionic liquids resulting in 24% certified power conversion efficiency under one sun.

16:00 - 16:20
2.3-I2
McGehee, Michael
University of Colorado Boulder
Why studying perovskite solar cells in reverse bias is surprisingly important
McGehee, Michael
University of Colorado Boulder, US

Michael D. McGehee is a Professor in the Chemical and Biological Engineering Department at the University of Colorado Boulder. He is the Associate Director of the Materials Science and Engineering Program and has a joint appointment at the National Renewable Energy Lab. He was a professor in the Materials Science and Engineering Department at Stanford University for 18 years and a Senior Fellow of the Precourt Institute for Energy. His current research interests are developing new materials for smart windows and solar cells. He has previously done research on polymer lasers, light-emitting diodes and transistors as well as transparent electrodes made from carbon nanotubes and silver nanowires. His group makes materials and devices, performs a wide variety of characterization techniques, models devices and assesses long-term stability. He received his undergraduate degree in physics from Princeton University and his PhD degree in Materials Science from the University of California at Santa Barbara.

Authors
Michael McGehee b
Affiliations
a, University of Colorado Boulder, US
b, National Renewable Energy Laboratory, US, Denver West Parkway, 15013, Golden, US
Abstract

Partial shading of a solar module can induce a set of cells within the module to operate under reverse bias. Previous studies have shown that metal halide perovskite solar cells with a wide variety of compositions and contacts exhibit interesting behavior in reverse bias that includes both reversible performance loss and non-reversible degradation. As metal-halide perovskite solar cells and photodetectors, which are often meant to be operated in reverse bias, reach ever closer to mass production, it is critical to understand how these devices behave under reverse bias. In this paper, we use an advanced drift-diffusion approach incorporating an electrochemical term to explain the short-circuit, open circuit and fill factor losses we experimentally measure after prolonged reverse bias. We show that holes can tunnel into the perovskite due to sharp band bending near the contact, accumulate within the bulk of the perovskite absorber, and trigger the oxidation of halides to form neutral halogens. The density of neutral halogens is much higher in reverse bias because there are hardly any electrons available to reduce the iodine. The resulting halogens act as bulk recombination centers. While the interstitial halogen density does decay when the cell is operated in forward bias, permanent degradation can occur if the iodine diffuses out of the perovskite layer.  We will discuss the implications of reverse bias degradation for both single and multijunction solar cells.

16:20 - 16:40
Discussion
16:35 - 16:40
SELFNC Closing
16:40 - 16:45
PEREMER Closing
16:40 - 16:45
PEROPV Closing
16:50 - 16:55
RETCHEM Closing
17:00 - 18:30
"Happy Hour": Do you want to stay in academia after your PhD? Why and how?
 
Posters
Bettina Baumgartner, Kenji Okada, Masahide Takahashi
Orientation of Metal-Organic Framework Films determined via Polarization-Dependent Infrared Spectroscopy
Can Lu, Adam Slabon
Interfacial Effects in Multi-Heterojunction Photoelectrodes for Photoelectrochemical Water Splitting
Arthur Markus Anton, Christian David Heinrich, Mukundan Thelakkat, Friedrich Kremer, Jenny Clark
Orientation and Order of Molecular Subunits and Excited State Dynamics of a Novel P3HT Bottlebrush Copolymer-
Rajashik Paul, Naveen Tailor, Heng Zhang, Hai Wang, Soumitra Satapathi
Decoding the Photophysical Phenomena of Charge Carrier Interplay in MAPbI3 and MAPbBr3 with Time Resolved THz Spectroscopy (TRTS) Study.
Huan Doan, Hoa Thi Nguyen, Valeska Ting, Xuan Nui Pham
Improved photodegradation of anionic dyes using a complex graphitic carbon nitride and iron-based metal-organic framework material
Lucie McGovern, Isabel Koschany, Gianluca Grimaldi, Loreta Muscarella, Bruno Ehrler
Grain Size Influences Activation Energy and Migration Pathways in MAPbBr3 Perovskite Solar Cells
Hakan Bildirir, Cuneyt Erdinc Tas, Oznur Karaoglu, Buket Alkan Tas, Erdal Ertas, Hayriye Unal
Improved Latent Heat Storage Properties Through Mesopore Enrichment of a Zeolitic Shape Stabilizer
José Catalán-Toledo, Francesc Bejarano, Jaume Veciana, Marta Mas-Torrent, Concepció Rovira, Núria Crivillers
Redox-active response of self-assembled AuNps on the liquid-liquid interface with alkyne-based Ferrocenyl Stilbene Analog
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