Sun May 12 2019
16:00 - 18:30
17:00 - 18:30
Mon May 13 2019
07:45 - 08:45
08:45 - 08:50
Announcement of the day
08:50 - 09:00
Session G1.1
Chair: Prashant Kamat
09:00 - 09:45
Miyasaka, Tsutomu
Toin University of Yokohama
Focusing key directions of perovskite photovoltaic R&Ds towards industrialization
Tsutomu Miyasaka
Toin University of Yokohama, JP

Tsutomu (Tom) Miyasaka received his Doctor of Engineering from The University of Tokyo in 1981. He joined Fuji Photo Film, Co., conducting R&Ds on high sensitivity photographic materials, lithium-ion secondary batteries, and design of an artificial photoreceptor, all of which relate to electrochemistry and photochemistry. In 2001, he moved to Toin University of Yokohama (TUY), Japan, as professor in Graduate School of Engineering to continue photoelectrochemistry. In 2006 to 2009 he was the dean of the Graduate School. In 2004 he has established a TUY-based company, Peccell Technologies, serving as CEO. In 2005 to 2010 he served as a guest professor at The University of Tokyo.

His research has been focused to light to electric energy conversion involving photochemical processes by enhancing rectified charge transfer at photo-functional interfaces of semiconductor electrodes. He has contributed to the design of low-temperature solution-printing process for fabrication of dye-sensitized solar cells and solid-state hybrid photovoltaic (PV) cells. Since the discovery of the organic inorganic hybrid perovskite as PV material in 2006 and fabrication of high efficiency PV device in 2012, his research has moved to R&Ds of the lead halide perovskite PV device. He has promoted the research field of perovskite photovoltaics by organizing international conferences and by publishing many papers on enhancement of PV efficiency and durability, overall citation number of which is reaching more than 5,000 times. In 2009 he was awarded a Ministry of Science & Education prize on his achievements of green sustainable solar cell technology. In 2017 he received Chemical Society of Japan (CSJ) Award. He is presently directing national research projects funded by Japan Science and Technology Agency (JST) and Japan Aerospace Exploration Agency (JAXA).

Tsutomu Miyasaka a
a, Graduate School of Engineering, Toin University of Yokohama, 1614, Kurogane-cho, Aoba, Yokohama, Kanagawa, Japan 225-8503

Organic inorganic lead halide perovskite materials have been matured in terms of conversion efficiency reaching the level exceeding those of CIGS and CdTe and approaching those of crystalline Si cells. In addition to high efficiency and high voltage, idiosyncratic merits of perovskite photovoltaic devices are lightweight and flexible body bearing thin and soft absorber film and ability to create a bifacial power generation device by utilizing semi-transparent absorbers, which enable use of the devices in the field where existing Si and CIGS cannot apply without extra cost of fabrication. For industrialization, remaining but serious issues of perovskite PV are reinforcing durability of performance against light and heat and replacement of lead with other environmentally acceptable metals. The former can be overcome by on-going compositional engineering, in particular innovation in developing all-inorganic materials. Further, heat resistance should not necessarily reach the level of Si because a major direction of perovskite PV in commercialization is applications in IoT society where temperature and light intensity environments are benign for perovskite and life of the power device can be as short as IoT devices. However, lead-containing device is not acceptable by the policy of industries rather than actual environmental impacts. In this viewpoint, development of non-lead type new perovskite absorbers is an urgent project for our next step of research. Further, lead-free materials can be invented without using organic cations. This direction of R&D leads to fabrication of non-lead, all inorganic PV devices, and is an important focus of our research to tackle. On the other hand, fundamental study for efficiency enhancement as the challenge to reach SQ limit should be directed to create a single cell capable of the performance approaching to those of GaAs [1]. For lead-based high performance perovskite solar cells, good news is that the device can have high stability, exceeding Si and GaAs, in applications to space satellites, thanks to thin film absorber and intrinsic defect tolerant properties of perovskites. Our recent examinations could reproduce the high stability against electron and proton radiations (published in iScience 2018 [2]) by using high efficiency versions of P3HT-based multi-cation perovskite cells. Needless to say, space industries require lightweight flexible device films loaded on the foldable wings of satellites. In IoT applications, perovskite devices were found to be operated with highest efficiency (>30%) under 200 lux indoor light, which exceeds the highest performance (exceeding amorphous Si) reached by dye-sensitized PV devices (>20%). Towards social implementation, my talk will be concerned with how to focus the strategies and challenges of compositional engineering in the community of perovskite PV.

09:45 - 10:15
Aernouts, Tom
Efficient Structures and Processes for Reliable Perovskite Solar Modules
Tom Aernouts
imec, BE

Dr Tom Aernouts is R&D leader of the Thin Film Photovoltaics group at imec. Over the last few years this activity has grown steadily with state-of-the-art work in organic solar cells and recently also perovskite-based photovoltaics, next to inorganic materials like Kesterites for future replacement of the currently strongly growing CIGS thin film solar cells. Also the lab environment was drastically improved with setting-up the O-line infrastructure in 2009 at imec, allowing the processing and characterization of thin film solar cells and modules with area up to 15 x 15 cm². A next upgrade in 2018 enabled to extend the device size to 35x35cm². Dr Aernouts earned his Master of Science and PhD degree in Physics (in 2006) at the Catholic University of Leuven, Belgium. Firstly, he worked on organic oligomer-based diode structures, afterwards continuing his research on organic photovoltaics at imec. There, his work focused on the processing and characterization of polymer-based organic solar cells and monolithic modules, introducing techniques like screen and inkjet printing. He has authored or co-authored more than 80 journal publications, book chapters and conference contributions. Also, his research group participates on a regular basis in a broad range of local and international projects, with the most recent example the coordination of the European H2020 project ESPResSo.

Tom Aernouts a
a, imec (partner in Solliance & EnergyVille), Kapeldreef 75, Leuven, 3001, Belgium.

Perovskite solar cell (PSC) technology has significant potential to revolutionise the photovoltaics (PV) industry due to high efficiencies and the potential for short energy payback periods in comparison to other established PV technologies making them truly competitive. Recently, solution processed PSCs have reached cell efficiency values rivalling those of established thin-film photovoltaic (PV) technology (CIGS, CdTe), even approaching crystalline Si (c-Si) records. The challenge is now to transfer this unprecedented progress from its cell level into a scalable, stable, low-cost technology on module level.

It will be key to bring forward technological solutions that combine high-throughput, low-cost manufacture of efficient and long-lasting PSC PV modules that can also have seamless integration in application areas that require customised end-products. This new approach is different to c-Si products produced as low-cost commodity products, in that customized products can create a high added value that allows for local production close to the end-user.

Therefore, at first substantial progress is targeted on cell efficiency, stability, and module process upscaling which enables to consolidate these results into glass-based modules at technology readiness level (TRL) 5. Demonstration of such modules in a high value application like building integrated PV (BIPV) facade element, supported with outdoor test results, opens then the door for technology validation at TRL6, for a fully integrated product.

Additionally other routes more towards customization and facilitation of integration are to be opened up. Novel processes will be initiated to allow transfer of the PSC technology from the glass-based platform to various flexible, plastic substrates. Additionally, novel interconnection schemes will be investigated to allow for easy variation in sizes and shapes of PSC modules. Options to realize semi-transparent device designs will be explored, for use as see-through PV modules for e.g. window integration or for tandem applications by stacking on top of existing (e.g. c-Si) PV technologies to boost the overall power conversion. Full technology validation of these novel routes in more specified applications is to be expected to occur in the coming years.

10:15 - 10:45
Hagfeldt, Anders
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
The Versatility of Mesoscopic Solar Cells
Anders Hagfeldt
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH

Anders Hagfeldt is Professor in Physical Chemistry at EPFL, Switzerland. He obtained his Ph.D. at Uppsala University in 1993 and was a post-doc with Prof. Michael Grätzel (1993-1994) at EPFL, Switzerland. His research focuses on the field of mesoporous dye-sensitized solar cells, specifically physical chemical characterization of mesoporous electrodes for different types of optoelectronic devices. He has published more than 370 scientific papers that have received over 35,000 citations (with an h-index of 90). He was ranked number 46 on a list of the top 100 material scientists of the past decade by Times Higher Education. In 2014, 2015 and 2016 he was on the list of Thomson Reuter’s Highly Cited Researchers. He is a member of the Royal Swedish Academy of Sciences, Stockholm, Royal Society of Sciences in Uppsala, and the Royal Swedish Academy of Engineering Sciences in Stockholm. He is a visiting professor at Uppsala University, Sweden and Nanyang Technological University, Singapore.

Anders Hagfeldt a
a, Laboratory of Photomolecular Science (LSPM), Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.

In our work on solid-state dye-sensitized solar cells (ssDSSC) we have recently shown that copper phenanthroline complexes can act as an efficient hole transporting material. We prepared ssDSCs with a novel organic dye WS-72 and [Cu(tmby)2]2+/+as redox system and achieved record power conversion efficiencies for ssDSCs of 11.7%. Our best DSC efficiency of 13.1% (32% for indoor ligh illumination) for a liquid Cu-complex electrolyte is achieved by the discovery that the PEDOT based counter electrode can be directly contacted with the dye/TiO2photoelectrode. Thus, there is no space between the two electrodes minimizing diffusion limitations and fill factors up to 0.8 is achieved.

In our work on perovskite solar cells (PSC) we have achieved efficiencies above 22% with a mixed composition of iodide/bromide and organic and inorganic cations. With the use of SnO2 compact underlayers as electron acceptor contacts we have constructed planar perovskite solar cells with a hysteresis free efficiency above 20%. Through the compositional engieneering larger preovskite grains grown in a monolithic manner are observed and reproducibility and device stability are improved. With regards to lifetime testing, we have shown a promising stability at 85 oC for 500 h under full solar illumination and maximum power point tracking (95% of the initial performance was retained). Recently, we have also commented on the standardization of PSC aging tests.

10:45 - 11:15
Coffee Break
Session G1.2
Chair: aleksandra djurisic
11:15 - 11:45
Chen, Lin
Northwestern University/ Argonne National Laboratory
Electronic Processes, Morphologies and Structural-functional Correlations in Conjugated Oligomers and Polymers for OPV and Photocatalysis
Lin Chen
Northwestern University/ Argonne National Laboratory
Lin Chen b
a, Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, United States
b, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinios 60439, United States

Conjugated polymers with charge transfer characters in a large extend are responsible for the recent advancement in organic photovoltaic (OPV) applications in bulk heterojunction (BHJ) devices. In the DOE-BES supported Energy Frontier Research Center (EFRC) Argonne-Northwestern-Solar-Energy-Research (ANSER) Center, we have carried out collaborative studies on electronic processes and in-situ morphological development of these low bandgap polymers and small molecules using ultrafast optical spectroscopy, static and in-situ grazing incident X-ray scattering (GIXS). Conventional organic photovoltaic models, in which donor molecules are treated as anonymous electron sources and charge carrier diffusion channels, are challenged by near-infrared transient absorption results of low bandgap polymers indicating strong correlations between intramolecular donor dynamics in < 100 fs and corresponding device power conversion efficiencies. The other conventional model being challenged is the driving force for exciton splitting in the bulk heterojunction environment which has been described by the LUMO-LUMO energy off-set between conjugated polymer electron donor and fullerene derivative electron acceptor. Our study suggests the intramolecular charge transfer characters must be combined with local and global conformations of conjugated polymer chains to achieve the low band gap.  Moreover, the morphology of the BHJ films is also investigated by in-situ GIWAS/GISAX methods including the effects of additives which suggest the interplays of the additives and the polymers in solution. The morphology of the heterojunction films has been correlated directly with the yield of the charge separation on time scales from femtosecond to microsecond. In addition, new photophysical studies are also carried out on a series of metal chelating conjugated polymers showing the capability and potential in photocatalytic hydrogen generation.

11:45 - 12:15
Kuno, Masaru
University of Notre Dame
Microscopic Measurements of Hybrid Perovskite Solar Cells
Masaru Kuno
University of Notre Dame, US
Masaru Kuno a
a, University of Notre Dame, Notre Dame, Indiana 46556, EE. UU., Notre Dame, US

This talk will focus on recent efforts to conduct local, spatially-resolved absorption/emission microscopy measurements on hybrid perovskite thin films.  Motivating these studies is the recent discovery that organometal halide perovskites such as methylammonium lead iodide (MAPbI3) possess impressive power conversion efficiencies when used as active layers in thin film solar cells.  Despite impressive performance gains realized in perovskite photovoltaics, much remains to be understood about their fundamental photophysics.  To illustrate, little is known about the role of compositional and/or morphological disorder in the optical and electrical response of these materials.  Additionally, effects such as light- and bias-induced anion and cation phase segregation as well as migration are known to alter the optical response of perovskite solar cells.  Consequently, a need exists for detailed microscopic studies of basic hybrid perovskite photophysics as well as spatially-resolved measurements to clarify their disorder-induced optical heterogeneities.  More recent work focuses on infrared imaging of cation migration in these materials.

12:15 - 12:45
Bolink, Henk
Universidad de Valencia - ICMol (Institute of Molecular Science)
Vapor Phase Deposited Single Junction and Tandem Perovskite Solar Cells.
Henk Bolink
Universidad de Valencia - ICMol (Institute of Molecular Science), ES

Hendrik (Henk) Bolink obtained his PhD in Materials Science at the University of Groningen in 1997 under the supervision of Prof. Hadziioannou. After that he worked at DSM as a materials scientist and project manager in the central research and new business development department, respectively. In 2001 he joined Philips, to lead the materials development activity of Philips´s PolyLED project.

Since 2003 he is at the Instituto de Ciencia Molecular (ICMol )of the University of Valencia where he initiated a research line on molecular opto-eletronic devices. His current research interests encompass: inorganic/organic hybrid materials such as transition metal complexes and perovskites and their integration in LEDs and solar cells.

Henk Bolink a
a, Universidad de Valencia - ICMol (Institute of Molecular Science), Catedrático José Beltrán Martinez 2, Paterna, ES

Organic-inorganic (hybrid) lead halide perovskites have recently attracted a self-standing, wide research field thanks to the demonstration of solar cells with rapidly increasing power conversion efficiencies (PCEs), now exceeding 20%. The interest toward these materials arises from the possibility of processing them into thin films by solution or vacuum techniques, which might lead to efficient and inexpensive photovoltaic devices. Hybrid perovskites have a wide spectrum of desirable properties; they are direct bandgap semiconductors with very high absorption coefficients, high and balanced hole and electron mobility, and large diffusion length. A unique feature of these materials is their versatility in terms of bandgap energy, which can be tuned by simple exchange of their components.Perovskite based solar cells, mostly employ solution processed perovskite layers. Evaporated methylammonium lead iodide perovskite layers have also been reported and been employed in solar cells. Our group has developed several perovskite based solar cells, using vacuum based perovskite preparation methods. These metal oxide free p-i-n type perovskite cells exhibit high power-conversion efficiencies. We have extended this work to fully evaporated perovskite devices reaching power conversion efficiencies as high as 20 % in a planar single junction device and similar performance in tandem devices. Avenues to further increase the device performance by using multiple cation perovskite prepared via sublimation will also be presented.                                                                                                                                                                                                                                                                                                                                                                                                                       

12:45 - 12:50
Sorbello, Luca
Greatcell Solar
Hyperion a bright future for solar simulators: The Greatcell Solar Italia way
Luca Sorbello
Greatcell Solar
Luca Sorbello a
a, Great Cell Solar

In the last decades to reproduce an AM1.5G spectrum, matching the A class, scientists were practically obliged to use expensive solar simulators mounting complex optics and using xenon arc bulbs as light sources. Such light source has multiple disadvantages and to this day spare bulbs are still quite expensive and with a limited life time (1000 h-1500 h) that make such technology not worth for long life testing, large area spot or frequent switching on and off.

In the last 5 years LED technology improved drastically and in the face of a constant improvement in quality, reliability and an increase in radiant power, a remarkable reduction in prices was observed, especially concerning critical bandwidth as the ones between 350 nm and 400 nm and the between 700 nm and 1100 nm. These allowed a very fast development of high efficient, long life, stable but expensive Solar Simulators based on LEDs technology.

Greatcell Solar Hyperion is, without doubts, a breakthrough on LED Solar simulators technology as it assures a high reliability, high accuracy and long life (>15000 h) at a very competitive price. Greatcell Solar Hyperion matches triple A+ class, respecting the most stringent international standards, over 16 cm X 16 cm spot (making it compatible i.e. with standard C-Si solar cells) and a triple A class over 22 cm X 22 cm illumination area, making it suitable to test multiple small and large areas devices.

Thanks to the innovative concept of Greatcell Solar Hyperion, it was possible to contain electrical consumption keeping the latter below a remarkable value of 600 W/h. Furthermore, through a dedicated driving software, it is possible to customise Hyperion spectrum modifying individually each one of the 20 LED families mounted. Greatcell Solar Hyperion LED solar simulator is was conceived as a modular structure, this opens the possibility to expand the illumination spot to host much larger substrates respect standard lab ones.

Greatcell Solar Hyperion can surely be considered a unique sun light emulator, capable to reproduce solar spectrum in a very faithful way as never done before with traditional xenon arc lamps sun simulators.

12:50 - 12:55
Dr. Gaebelein, Dirk
TCI Deutschland GmbH
TCI Industry talk
Dirk Dr. Gaebelein
TCI Deutschland GmbH
Taro Tanabe a
a, TCI

TCI is a leading global manufacturer of fine and specialty chemicals for research and industry. We offer and manufacture more than 29,000 research chemicals using our own facilities. Many of these chemicals are highly specialized, including a large number of reagents available only through TCI.

TCI is able to supply a wide selection of Fine and Specialty Chemicals by drawing upon our expertise of manufacturing techniques. With proven production experience and varied reaction capabilities, which rank us among the best in the industry, TCI can supply most compounds in sizes ranging from milligram to bulk scale.

TCI’s continuously expanding research and development, modern manufacturing facilities and quality assurance/control laboratories allows us to offer a wide range of products and services. You can count on TCI as your partner for products as well as custom solutions.

In pursuit of meeting customer demands, we have developed a worldwide network of effective communication and shared capability, which enables us to deliver our high quality reagents rapidly to customers across the globe from our offices and plants in North America, Europe, China and India.

We will continue to persevere in our efforts in “Moving Your Chemistry Forward".

12:55 - 13:00
Hebting, Yanek
Greatcell Solar Materials Pty Ltd
Innovative Materials for Innovative Technologies
Yanek Hebting
Greatcell Solar Materials Pty Ltd, AU
Yanek Hebting a
a, Greatcell Solar Materials Pty Ltd, Faunce Street, 28, Queanbeyan East, AU

As your trusted provider of Perovskite Solar Cells (PSC) and Dye Solar Cells (DSC) materials, Greatcell Solar Materials (GSM) aims to be the one-stop shop for researchers and industrialists. With the objective of optimizing performance and stability of PSC devices, GSM offers a wide range of ammonium halides (e.g. iodides, bromides and chlorides) and pseudo-halides (e.g. thiocyanates, tetrafluoroborates, hexafluorophosphates) designed to be used as replacement or dopant in existing compositions to investigate and optimize various device parameters. All materials are exclusively manufactured in our Australian facility and produced to stringent quality standards.

GSM is continuously expanding its development of innovative materials. As such, a range of ammonium carboxylates (acetates and trifluoroacetates) have recently been developed and are currently on offer.

GSM will continue to offer Dyes, Metal Oxide Pastes and Conductive Pastes it has previously developed for the industrialisation of DSC technology.

GSM is capable and ready for the industrialisation of DSC and PSC technologies. GSM is also aiming at providing materials for the commercialisation of innovative perovskite-based applications such as optoelectronic, piezoelectric and ferroelectric devices as well as molecular switches.

13:00 - 14:30
Lunch Break
Session A1
Chair: Shane Ardo
14:30 - 15:00
Meggiolaro, Daniele
Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM
Defects Chemistry and Charge Traps in MA(Pb,Sn)I3 Perovskites: A Computational Perspective
Daniele Meggiolaro
Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, IT
Daniele Meggiolaro a, b
a, Istituto Italiano di Tecnologia (IIT), Genova, Italy, Via Morego, 30, Genova, IT
b, Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, Via Elce di Sotto 8, 06123 Perugia, Italy

Lead halide perovskites are promising materials for photovoltaics, exceeding 22% of efficiency in solar cells devices.[1] Recently, mixed Pb-Sn and lead-free perovskites (MASnI3) have gain great interest due to the reduced toxicity compared to full-lead perovskites and the possibility of tuning the band gap to lower values. While the  partial substitution of Pb with Sn in mixed Pb-Sn perovskites has been demonstrated a successfull strategy to decrease the toxicity of these materials with limited impact on the overall efficiency (~17%),[2] the use of full tin MASnI3 perovskites is still limited due to self-doping phenomena which have detrimental effects on the charge carriers lifetimes and on the efficiencies in solar cell devices (<6%).[3]  

In this presentation a comparative study of native defects in MAPbI3 and MASnI3 perovskites based on state of the art Density Functional Theory (DFT) is presented. The nature of deep charge traps in these materials and the associated defects chemistry is investigated by the analysis of the defects formation energies in different conditions of growth and of the associated thermodynamic ionization levels.[4] This study aims to illustrate the most relevant similarities and differences in the defects chemistry of these materials. Starting from the analysis of MAPbI3 defects chemistry, the effects of partial Pb substitution by Sn will be discussed, by focussing on the potential holes self-trapping processes that Sn-doping can induce in the perovskite. Thus, the discussion moves to show results concerning the defects chemistry of full tin MASnI3 perovskite. Our analysis reveals that while in the full-lead perovskite iodine play a prominent role in determining the defects chemistry by modulating the relative trapping activity, in full-tin perovskites the different electronic structure and the high propensity of Sn to oxidation lead to a different defects chemistry scenario. Furthermore, a possible origin of the p self-doping in Sn-perovskites related to the high stability of tin vacancies in this system is discussed.

15:00 - 15:15
Motti, Silvia
University of Oxford
Defect Activity in Lead Halide Perovskites
Silvia Motti
University of Oxford, GB
Silvia Motti a, b, c, Daniele Meggiolaro d, e, Alex Barker b, Carlo Perini b, c, James Ball a, b, Marina Gandini b, c, Roberto Sorrentino b, c, Min Kim b, Filippo de Angelis d, e, Annamaria Petrozza b
a, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, GB
b, CNST, Istituto Italiano di Tecnologia, Milano
c, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, Milano, IT
d, Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, Via Elce di Sotto 8, I-06123, Perugia, IT
e, Istituto Italiano di Tecnologia (IIT), Genova, Italy, Via Morego, 30, Genova, IT

Perovskite semiconductors have proven to be very promising for photovoltaic application in the last years. Great research effort has been employed towards understanding how the perovskite crystalline and electronic structure relates to their remarkable defect tolerance and surprisingly long carrier lifetimes and high open circuit voltages. At the same time, the material instability often interferes with experimental observations, besides posing a major challenge for commercial application.[1–3] We report a comprehensive investigation of defect activity in lead halide semiconductors combining computational studies with experimental evidences obtained from transient photocurrent, transient absorption and steady-state and time resolved photoluminescence spectroscopy. We have identified the most relevant point defects in MAPbBr3 and MAPbI3 and found that the low trapping and trap-assisted recombination rates associated with electron trapping sites make these a less efficient loss channel when compared to hole trapping defects, therefore the predominance of electron traps can contribute to enhance radiative efficiency and solar cell open circuit voltage.[4,5] We also demonstrate the reactivity of defects and how it relates to the response of the material to external stimuli (i.e. atmosphere, photoexcitation), explaining the photoinstabilities observed in these materials, such as the photoinduced quenching and brightening of photoluminescence and atmosphere induced passivation. This understanding allows us to propose surface engineering methods that effectively block under-coordinated sites, favoring defect healing over defect formation and enhancing the material stability while also improving solar cell open circuit voltage.[6] Our findings on the interplay between defect chemistry and semiconductor performance sheds light to the factors in play regarding the material optimization during the last years of research. Moreover, it also opens the possibility of developing intelligent fabrication methods and further optimizing performance and stability of the material.

15:15 - 15:30
Sajedi Alvar, Mohammad
Max Planck Institute, Stuttgart
Concentration and Mobility of Ions in Methylammonium Lead Iodide Thin Films from Dielectric Response
Mohammad Sajedi Alvar
Max Planck Institute, Stuttgart, DE
Mohammad Sajedi Alvar a, Gert Jan Wetzelaer a, Paul Blom a
a, Max Planck Institute for Polymer Research, Mainz, Germany, Ackermannweg, 10, Mainz, DE

Concentration and Mobility of Ions in Methylammonium Lead Iodide Thin Films from Dielectric Response


M. Sajedi Alvar, G.A.H. Wetzelaer and P.W.M. Blom


Max Planck Institute for Polymer Research, Ackermannweg10, 55128 Mainz, Germany

For a quantitative modelling of devices based on methylammonium lead iodid (MAPbI3) understanding of its dielectric properties are indispensable. Ion migration plays an important role in the magnitude and frequency dependence of the dielectric constant of MAPbI3.  From impedance spectroscopy measurements on Au/MAPbI3/Au capacitors we have extracted a diffusion coefficient for positive ions of 1×10-15 m2/s.  This diffusion coefficient has been verified by measuring the dielectric displacement as a function of frequency. From the magnitude of the dielectric displacement an ion concentration of 2×1025 m-3 is obtained. Using drift - diffusion numerical simulations the effect of ion motion and voltage scan speed on the electric field distribution in MAPbI3 based devices can be predicted.  

15:30 - 15:45
Senocrate, Alessandro
Max Planck Institut for Solid State Research
Slow methylammonium migration in methylammonium lead iodide in the dark and under illumination
Alessandro Senocrate
Max Planck Institut for Solid State Research, DE
Alessandro Senocrate a, b, Igor Moudrakovski a, Tolga Acartuerk a, Gee Yeong Kim a, Rotraut Merkle a, Ulrich Starke a, Michael Graetzel a, b, Joachim Maier a
a, Max Planck Institut for Solid State Research, Heisenbergstr. 1, Stuttgart, 70569, DE
b, Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, Lausanne, CH

Ionic conductivity in methylammonium lead iodide (MAPbI3) and related compounds has received considerable attention after significant ion-induced polarisation phenomena have been observed in perovskite solar cell devices under operation.[1-3] Such polarization processes can affect both charge transport in the bulk of the material and charge extraction at the interfaces of a device, making a comprehensive knowledge of the nature of this process of utmost importance to understand and possibly improve halide-perovskite-based solar cell devices. While the existence of a significant iodine motion in MAPbI3 is now largely accepted,[4] the presence and extent of methylammonium motion is a more controversial topic. Here,[5] we investigate methylammonium transport in methylammonium lead iodide in the dark and under illumination by using tracer diffusion and 1H and 13C solid-state NMR. We observe a perceptible, but very sluggish, MA motion, and we extract the corresponding diffusion coefficient. The derived bulk conductivity is found to be orders of magnitude below the experimental ionic conductivity, corroborating the picture of pure iodine transport in MAPbI3 both in the dark and under illumination.

15:45 - 16:00
Futscher, Moritz
Ion Migration in Triple-Cation Mixed-Halide Perovskite Solar Cells with Potassium Passivation
Moritz Futscher
Moritz Futscher a, Lucie McGovern a, Kangyu Ji b, Sandy Sanchez c, Sam Stranks b, Bruno Ehrler a
a, Center for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
b, Cavendish Laboratory, Department of Physics, University of Cambridge, UK, JJ Thomson Avenue, Cambridge, GB
c, Adolphe Merkle Institute, Chemins des Verdiers 4, CH-1700 Fribourg

Solar cells based on halide perovskites show efficiencies close to highly-optimized silicon solar cells. However, ions migrating in these perovskites lead to device degradation and complicate the characterization of perovskite solar cells. We recently showed that transient ion-drift is a powerful method to quantify activation energy, concentration, and diffusion coefficient of mobile ions in perovskite solar cells. By studying methylammonium lead triiodide (MAPbI3) we found that both MA+ and I- ions migrate at room temperature, but with very different diffusion coefficients (10-9 and 10-12 cm2s-1 respectively).

Recently it was shown that introducing potassium into triple-cation mixed-halide perovskites passivates surfaces and stabilizes luminescence without compromising charge transport or extraction. [1] This has been attributed to the mitigation of both non-radiative losses and ion migration in perovskite films. Using transient ion-drift, we study ion migration in these triple-cation mixed-halide perovskites and find that the migration of mobile halide ions is comparable across different device geometries, but that the diffusion coefficient of mobile halide ions is two orders of magnitude lower than in MAPbI3 perovskites. We find no evidence of mobile cations, suggesting that cation migration is impeded in mixed-cation mixed-halide perovskites. We furthermore find that the activation energy of mobile halide ions in these triple-cation mixed-halide perovskites is not influenced by potassium passivation, but that the concentration decreases and the diffusion coefficient increases with increasing potassium passivation. This quantification of mobile ions in triple-cation mixed-halide perovskites will lead to a better understanding of ion migration and the influence of passivating agents on that migration.

16:00 - 16:30
Coffee Break
16:30 - 16:45
Van Brackle, Charles
University of North Carolina – Chapel Hill
Defect Passivation in Halide Perovskites
Charles Van Brackle
University of North Carolina – Chapel Hill, US
Jinsong Huang a, Charles Van Brackle a
a, University of North Carolina – Chapel Hill, 1112 Murray Hall Chapel Hill, NC 27599, North Carolina, US

Passivation of electronic defects at the surface and grain boundaries of perovskite materials has become one of the most important strategies to suppress charge recombination in both polycrystalline and single crystalline perovskite solar cells. Although many passivation molecules have been reported, it remains very unclear on the passivation mechanisms of various functional groups. Here, we systematically engineer the structures of passivation molecular functional groups, including carboxyl, amine, isopropyl, phenethyl and tert-butyl-phenethyl groups, and study their passivation capability to perovskites. It reveals the carboxyl and amine groups would heal charged defects via electrostatic interactions, and the neutral iodine related defects can be reduced by the aromatic structures. The judicious control of the interaction between perovskite surface and molecules can further realize the grain boundary passivation, including those are deep toward substrates.  Understanding of the underlining mechanisms allows us to design a new passivation molecule yielding high-performance p-i-n structure solar cells with a stabilized efficiency of 21.4%. The open-circuit voltage (VOC) of a device with perovskite optical bandgap of 1.57 eV reaches 1.23 V, corresponding to a record low VOC deficit of 0.34 V. Our findings provide a guidance for future design of new passivation molecules to realize multiple facets applications in perovskite electronics. The impact of defect passivation on device stability will also be discussed. 

16:45 - 17:00
Kaiser, Waldemar
Technical University Munich
3D Simulation of Ion Migration within the Microstructure of Perovskite Solar Cells
Waldemar Kaiser
Technical University Munich
Waldemar Kaiser a, Nga Phung b, Antonio Abate b, Alessio Gagliardi a
a, Department of Electrical and Computer Engineering, Technical University of Munich
b, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, Berlin, DE

Perovskite solar cells (PSCs) have gathered a large interest in the photovoltaic community due to their remarkable optoelectronic properties [1]. Low-temperature processed PSCs show sharp optical absorption edges, low bulk recombination, high charge carrier diffusion lengths, and a high light power conversion efficiency. Major remaining challenges with PSCs are the content of toxic lead, hysteresis effects, and the long-term stability of the material.

Although the quality of thin film PSCs has been enhanced successfully, grain boundaries (GBs) are still present within fabricated thin film devices. The perovskite film microstructure has a significant impact on the performance of the PSCs. Existing studies provided evidence for a strong correlation between ion migration and grain boundaries and emphasized the significance for stability and hysteresis effect during device operation [2,3]. Despite the rapid progress in the understanding of the role of interfaces within perovskite thin films [4,5], several aspects, such as the role of interfaces on the ion dynamics and charge carrier recombination, need both further experimental and theoretical investigations. Present numerical models are mainly based on 1D drift-diffusion simulations, which allow a simplified analysis of trap states [6, 7] and grain boundaries [8]. Ion densities covering a range from 1015 cm-3 [8] up to 1019 cm-3 [7,8] have been used in the numerical analysis to fit the experimental results. As the migration of ions and the distribution of trap states strongly depend on the microstructure of the  PSCs, a 3D numerical device model is required to study the relation between the grain boundaries and the PSC performance.

In this work, we present a joint theoretical-experimental investigation on the role of the microstructure of the perovskite thin film on the device performance. We develop a 3D kinetic Monte Carlo (kMC) model to simulate the PSCs including realistic grain morphologies, the dynamics of ions and photo-generated charge carriers, and recombination processes. The large difference in the diffusivity of ions and photo-generated charge carriers is handled by a multi-timescale approach, which solves the dynamics of ions and charge carriers separately, while the Coulomb interaction between ions and charge carriers is accounted for by an electrostatic background potential. This allows to perform transient device simulations despite the slow motion of ions. The kMC model is used to analyze the time-dependent response of the device performance as a function of charge accumulation within grain boundaries. We study the impact of (i) ion migration and (ii) trap states for different grain sizes and structures on the jV-characteristics of the PSC. The observed results are used to analyze transient current measurements of devices with different grain sizes. We observe that the screening of ions can be reduced by the presence of GBs, with the drawback of increased trap-assisted recombination at the GBs.

17:00 - 17:15
Kim, Geeyeong
Max Planck Institute for Solid State Research, Stuttgart
Equilibrium space charges effect at halide perovskite interactions: The role of ionic charge carriers
Geeyeong Kim
Max Planck Institute for Solid State Research, Stuttgart, DE
Gee Yeong Kim a, Alessandro Senocrate a, David Moia a, Joachim Maier a
a, Max Planck Institute for Solid State Research, Stuttgart, Heisenbergstraße, 1, Stuttgart, DE

Methylammonium lead iodide (MAPI), which is the halide perovskite that is currently in the focus of photovoltaic research because of its high conversion efficiencies. In this contribution we discuss equilibrium space charge effects in MAPI and concentrate on the MAPI/TiO2 and MAPI/Al2O3 contacts. Irrespective of polarization phenomena building up under operation, already the equilibrium situation is dominated by space charge effects (built-in space charge). While such equilibrium space charge effects are only considered in terms of electronic charge carrier redistribution, we will apply a generalized picture that discusses both ionic and electronic redistribution. We fine that ionic carriers are not only relevant, but they even dictated the space charge potential which the electrons have to follow (fellow-traveler effect). Our analysis is based on the measurement of electronic and ionic conductivities in MAPI/TiO2 and MAPI/Al2O3 composites, a technique that has been successfully applied in solid states ionics [1-3]. Those findings give strong indications of ionically-driven equilibrium space potentials forming at the MAPI/TiO2 and MAPI/Al2O3 interfaces. This study provides a completely new perspective for interfacial research in lead halide perovskites.

[1] J. Maier, Nature Mater. 2005, 4, 805.

[2] J. Maier, Phys. Chem. Chem. Phys. 2009, 11,3011-3022.

[3] H. Yamada, A. J. Bhattacharyya, J. Maier, Adv. Func. Mater. 2006, 16, 525-530.

17:15 - 17:30
Yang, Terry Chien-Jen
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
Photoinduced Halide Segregation and Diffusion in Mixed-halide Perovskite Solar Cells
Terry Chien-Jen Yang
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH
Terry Chien-Jen Yang a, Pietro Caprioglio c, d, Fan Fu a, Peter Fiala a, Martin Stolterfoht c, Florent Sahli a, Ricardo Razera a, e, Matthias Bräuninger a, Steve Albrecht d, Dieter Neher c, Quentin Jeangros a, Christophe Ballif a, b
a, École Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Switzerland, Rue de la Maladière, 71, Neuchâtel, CH
b, CSEM, PV-Center, Jaquet-Droz 1, 2002 Neuchâtel, Switzerland
c, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm, Germany
d, Young Investigator Group Perovskite Tandem Solar Cells, Helmholtz-Zentrum Berlin, Berlin, DE
e, PGMICRO, Instituto de Física, UFRGS, Av. Bento Gonçalves 9500, Porto Alegre-RS, Brazil

Photoinduced halide segregation, a phenomenon first shown by Hoke et al. [1] (2014) via photoluminescence (PL) peak shifting over time, poses a serious problem for high-bandgap mixed-halide perovskites which are used in high-efficiency multijunction solar cells (e.g. perovskite-silicon, perovskite-Cu(In,Ga)Se2 and perovskite-perovskite tandems) [2]. The main issue is that a proportional increase in bandgap with increasing bromide-to-iodide ratio does not yield the same increase in open-circuit voltage, thus limiting their performance. In this work, we investigate the diffusion controlled mechanisms behind photoinduced halide segregation in long-term stable cesium-formamidinium perovskites, fabricated via a 2-step hybrid deposition technique [3], as well as fully evaporated all-inorganic Cs-based perovskites. Temperature-dependent PL show distinct peak shifts attributed to the parting of iodide and bromide into separate domains, while the diffusion process slows down and eventually stops with a decrease in temperature. Therefore, solid-state diffusion models [4] can be used to fit the temperature-dependent PL of these mixed iodide-bromide compositions providing quantitative insights into the diffusion controlled mechanisms. In addition to peak shifting, for some samples, absolute PL measurements revealed increasing PL quantum yields in excess of 22% over time under constant illumination, after the phases segregate. The influence of this photoinduced halide segregation and diffusion on perovskite solar cell properties will be discussed at the conference.

Session B1
Chair: Henk Bolink
14:30 - 14:45
Holst Centre/TNO – Solliance - NL
Roll-to-roll slot-die coating of perovskite solar cells with efficiencies up to 13.5%: perspectives from the current status and further potential improvements
Holst Centre/TNO – Solliance - NL, NL
Ilker Dogan a, Francesco Di Giacomo a, Henri Fledderus a, Harrie Gorter a, Gerwin Kirchner a, Ike de Vries a, Sjoerd Veenstra a, Pim Groen a, Ronn Andriessen a, Yulia Galagan a
a, TNO Solliance

Organometallic halide perovskites are promising materials for photovoltaic applications, with achieved efficiencies over 23% at lab-scale. For promoting the use of perovskite solar cells (PSCs) in practical applications, it is essential to achieve an upscaling route, which ensures environmentally friendly processing of stable and highly efficient PSCs. In this presentation, we demonstrate and discuss the feasibility of upscaled production of PSCs via roll-to-roll (R2R) slot-die (SD) coating route. One of the main parts of the presentation involves how we have achieved these results with solvent selection & optimization. Most of the solvents used to prepare the inks for charges transport and absorber layers are toxic, carcinogenic, or harmful to environment. Being an ambient-exposed coating technique, most of the solvents for preparing the inks for layers has to be replaced by safer alternatives. Apart from that, as a result of high roll speeds, fast crystallization kinetics have to be investigated and implemented (preferably under ambient conditions) in order to obtain a uniform coating with desired morphology. We have performed R2R SD coating runs of electron transport layers and perovskite absorber layers on flexible substrates with a width of 30 cm and a web speed of 3-5 m/min, and developed layer drying methods for R2R coating. The stacks were completed by coating the hole transport layer using sheet-to-sheet (S2S) SD processing. The average stabilized power conversion efficiencies obtained from this n-i-p configurated stack reached to an average value of 12% (measured over different areas) and with the best value of 13.5%. This demonstrated value is an achievement towards future commercialization of large scale processing of PSCs. In addition, we currently investigate the R2R coating of perovskite layers on R2R-coated hole transport layers in order to realize p-i-n configuration. At this stage, this investigation focuses on the realization of uniform and pinholes-free coatings of perovskite and hole transport layers. Finally, we briefly demonstrate our initial results on flexible perovskite tandem solar cells realized by spin coating, yielding an efficiency of 21.5%, and we discuss the potential of scalability of this lab-scale cell.

14:45 - 15:00
Kosasih, Felix Utama
University of Cambridge - UK
Visualisation and Elemental Analysis of Perovskite Damage in Laser Scribing of Perovskite Solar Modules
Felix Utama Kosasih
University of Cambridge - UK, GB
Felix Utama Kosasih a, Lucija Rakocevic b, c, Jef Poortmans b, c, Caterina Ducati a
a, Department of Materials Science and Metallurgy, University of Cambridge, UK, Charles Babbage Road, 27, Cambridge, GB
b, IMEC– Solliance, Thin Film PV, Kapeldreef 75, B-3001 Leuven, Belgium
c, Department of Electrical Engineering, KU Leuven, Kasteelpark Arenberg 10, 3001 Heverlee, Belgium.

Perovskite solar cells’ power conversion efficiency has reached an impressive 23.7% [1] after vast improvements in material and fabrication techniques, but their widespread application is hampered by challenges in upscaling lab-sized cells into large modules. One enabling step in the upscaling process is laser scribing, in which a multilayer solar module is divided into series-connected cells by 3 scribe lines using a pulsed laser beam. So far, in active area and efficiency calculations it has been assumed that this laser beam does not damage the perovskite layer beyond the scribe lines themselves.

In this work, we aim to investigate the validity of this assumption by comparing modules scribed with a pulsed laser beam to that mechanically scribed with a knife. Specifically, we focus on the P3 scribe which removes the top metal contact from a module stack. We used focused ion beam milling to cut a lamella immediately adjacent to a P3 scribe. Then, we studied the samples with cross-sectional high-angle annular dark field (HAADF) imaging and energy-dispersive X-ray spectroscopy (EDX) in a scanning transmission electron microscope (STEM) to directly visualise laser damage on this slice of the module. We subsequently applied three multivariate statistical analysis algorithms to denoise and decompose our data sets, namely principal component analysis, independent component analysis, and non-negative matrix factorisation. These algorithms enabled acquisition of meaningful data with high signal-to-noise ratio while minimising beam current and dwell time. Plotting the brightness of our HAADF images showed lower intensity in the perovskite layer of laser scribed modules, indicating a loss of heavy elements such as lead or iodine. Meanwhile, an analysis of the EDX data revealed a much higher prevalence of PbI2 flakes in the perovskite layer of laser scribed modules, suggesting laser-triggered decomposition of perovskite into PbI2. Furthermore, we also investigated the effects of laser power, perovskite deposition method, and ablation depth on the extent of damage. Finally, we conducted top-view EDX scans in a scanning electron microscope to examine the integrity of the indium tin oxide contact, which must not be damaged by the P3 scribe. We anticipate that this work will help the perovskite photovoltaics community to further optimise the laser scribing process, simultaneously minimising the width of dead area and perovskite damage.

15:00 - 15:15
Matteocci, Fabio
CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’
Long-Term Stability of Large Area Perovskite Solar Cell under Thermal Stress
Fabio Matteocci
CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, IT
Fabio Matteocci a, Emanuele Calabrò a, Diego Di Girolamo b, Enrico Lamanna a, Danilo Dini b, Aldo Di Carlo a
a, CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, Via del Politecnico, 1, Roma, IT
b, Dept. of Chemistry, University of Rome Sapienza, P.le A. Moro 5, 00185 Rome,Italy

The stability of the perovskite solar cell is the main topic for the validation of this photovoltaic technology at the industrial level. One of the major challenging topic is the achievement of the thermal stability measured following IEC protocols. Several degradation factors play a crucial role on the stability issue such like the contact migration and the iodine leakage in the perovskite absorber[1]. In this work, we will show how the the thermal stress at 85°C affects the performance of the perovskite solar cell in air. In particular, the open circuit voltage and the fill factor are the main parameters responsible of the decrease in power conversion efficiency[2]. We tested several type of encapsulated devices where the perovskite, the architecture and the interface are designed in order to evaluate the best strategy to achieve long-term stability. The results show that both nip and pin architectures suffer about the electrode migration especially when the electrode is thermally evaporated. Alternative electrodes based on ITO and Carbon are introduced to mitigate this effect. Furthermore, the role of the interfaces between the constituent layers will be reported by varying the perovskite composition and additives. Thanks to the optimization of the contact and the interfaces, T80 lifetime of more than 500 hours will be presented for both architectures.

15:15 - 15:30
Sahli, Florent
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
Perovskite/Silicon Monolithic Tandem Based on a P-type High-temperature Tolerant Silicon Bottom Cell
Florent Sahli
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH
Florent Sahli a, Gizem Nogay b, Jérémie Werner a, c, Fan Fu a, Arnaud Walter b, Saeid Rafizadeh b, Vincent Paratte a, Raphäel Monnard a, Brett A. Kamino b, Peter Fiala a, Terry Chien-Jen Yang a, Matthias Bräuninger a, Ricardo A. Z. Razera a, Matthieu Despeisse b, Sylvain Nicolay b, Mathieu Boccard a, Andrea Ingenito a, Quentin Jeangros a, Christophe Ballif a, b
a, École Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Switzerland, Rue de la Maladière, 71, Neuchâtel, CH
b, CSEM, PV-Center, Jaquet-Droz 1, 2002 Neuchâtel, Switzerland.
c, ǂ now at University of Colorado Boulder, Colorado, USA.

Increasing the power output per unit area is the most promising way to further decrease the levelized cost of electricity (LCOE) of crystalline silicon (c-Si) photovoltaics. In this regard, adding a wide-bandgap top cell to c-Si can reduce thermalization losses and enables the cell to surpass the theoretical efficiency limit of single-junctions. Organic-inorganic perovskite solar cells have been identified as promising partners for silicon solar cells due to their high power conversion efficiency at the single-junction level, sharp absorption edge, and potentially low fabrication costs. Because of these attributes, perovskite/c-Si tandems have the potential to achieve efficiencies >30% at a competitive LCOE, with a current record efficiency of 28%. Until now, all published perovskite/c-Si devices with efficiencies over 25% have featured an n-type silicon heterojunction (SHJ) bottom cell.1-4 While this type of cell can reach high efficiencies, the low thermal stability of the passivating and selective amorphous silicon layers of SHJ cells limit the perovskite top cell processing to temperatures below 250°C, which limits the choice of charge-selective contact materials. In contrast to mainstream contacting schemes, the low processing temperature of SHJs does not trigger any improvement of the wafer through impurity gettering and/or thermal donor deactivation, preventing the use of low-quality p-type wafers routinely used in the industry. Here we demonstrate the first tandem solar cell featuring a p-type bottom silicon cell based on passivating contacts formed at high temperatures,5 achieving a steady-state efficiency of 25.1%. This value is on par with our record tandems made with n-type SHJs. The c-Si bottom cell fabrication reported here is compatible with the high-temperature emitter diffusion processes used today in the c-Si PV industry. In addition, the high-temperature tolerance of the bottom silicon cell allows using charge-selective contacts formed at high temperatures such as m-TiOx, c-TiOx, NiOx, SnOx for an improved top cell efficiency.

15:30 - 16:00
Di Giacomo, Francesco
Towards Stable Perovskite Solar Modules Made by Sheet to Sheet and Roll to Roll Fabrication
Francesco Di Giacomo
Francesco Di Giacomo a, Henri Fledderus a, Ilker Dogan a, Wiljan Verhees a, Valerio Zardetto a, Claire Burgess b, Meherdad Najafi a, Dong Zhang a, Harrie Gorter a, Gerwin Kirchner a, Ike de Vries a, Herbert Lifka a, Yulia Galagan b, Tom Aernouts c, Mariadriana Creatore b, Pim Groen a, Sjoerd Veenstra a, Ronn Andriessen a
a, TNO – partner in Solliance, PO Box 8550, 5605KN Eindhoven, The Netherlands
b, Department of Applied Physics – partner in Solliance, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
c, Imec – partner in Solliance – Thin-Film PV group, Thor Park 8320, 3600 Genk, Belgium


  The main challenges in the industrial development of the perovskite solar cell (PSC) technology is the upscaling of the deposition of the electro-active layers and the poor stability of PSC devices, which can hinder the path towards commercialization. In this work we will present the transition made in Solliance from lab-scale to a large area fabrication process: first by sheet-to-sheet (S2S) and later by a high-throughput roll-to-roll (R2R) production, using a combination of slot die coating, (spatial) atomic layer deposition (ALD) and sputtering. We will also demonstrate that with the developed S2S deposition processes it is possible to achieve thermal stability at 85°C for 100 cm2 PSC modules.


  The S2S perovskite ink formulation and coating/drying process were first optimized in a nip architecture: in this way it was possible to fabricate 144 cm2 modules with 13.8% stabilized aperture PCE with no losses with respect to equivalent lab-scale cell of 0.09 cm2, an up-scaling of more than three orders of magnitude. For the sake of stability, the same perovskite layer was transferred to a pin stack. Slot die coating was used for the NiOx hole transport, the perovskite and the PCBM layers, while a combination of (conventional or spatial) ALD and sputtering of ITO were introduced as scalable techniques for the deposition of the semitransparent top electrode. Large area coated non-transparent and semitransparent pin cells with stabilized PCE of up to 17% and 15% respectively were fabricated, with equivalent minimodules of 4 cm2 displaying stabilized aperture PCE of 14.3% and 13.6% respectively. Thanks to the introduction of compact metal oxide ETL by ALD and the use of sputtered ITO the semitransparent cells can retain 90% of the initial PCE after 1000h of continuous light soaking or 1000h of thermal stress at 85°C (as much as the lab-scale devices). In addition to this result, a 100 cm2 semitransparent module with 12% stabilized aperture PCE will be presented. Remarkably also the 100 cm2 module can withstand 1000h of thermal stress at 85°C with only 10% losses.


To further reduce the production cost of PSC, a R2R coating process has been developed in parallel to S2S. An environmentally acceptable solvent was introduced, to avoid using volatile carcinogenic, mutagenic or reprotoxic compounds. By using two R2R coated electro-active layers, 10 cm2 and 160 cm2 flexible modules with stabilized aperture PCE of 12.3 and 10.1% were demonstrated. In a next step, by applying three consecutive R2R coated electro-active layers, stabilized cell efficiencies up to 16% have been achieved. These R2R deposition processes are now being adapted to a pin architecture to fabricate stable flexible PSCs. The obtained results demonstrate that low-cost, stable, low-temperature and large area manufacturing of perovskite solar modules is within reach by using both S2S and R2R processes.


16:00 - 16:30
Coffee Break
16:30 - 16:45
Lutsen, Laurence
Towards 2D Layered Hybrid Perovskites with Enhanced Functionality
Laurence Lutsen
Laurence Lutsen a, Dirk Vanderzance a, b, Wouter Van Gompel b, Roald Herckens b, Paul-Henri Denis b, Martijn Mertens b, Tom Aernouts c, Jan D'Haen d, Bart Ruttens d, Kristof Van Hecke e
a, 1 IMEC, Imomec, Diepenbeek (Belgium)
b, Hasselt University, WET/OBPC/HyMat, Diepenbeek (Belgium)
c, IMEC, Leuven, Leuven, BE
d, Hasselt University, IMO, Diepenbeek (Belgium)
e, Gent University, Department of Chemistry, Gent (Belgium)

Recently organic-inorganic perovskite hybrid materials have been developed for solar cell applications reaching record efficiencies of more than 23%. Furthermore, these materials allow to move from a fundamentally 3D structure using small organic molecules to essentially 2D layered structures using larger organic molecules. This opens an avenue towards a quite new class of organic-inorganic nanocomposites in which the inorganic perovskite sheet acts as a template for the self-assembly of organic chromophores confined between the sheets of the inorganic layer. Thus the complexity of the organic interlayer in organic-inorganic hybrid perovskites can be increased by introducing additional secondary interactions between different organic components, e.g. pi-interactions. A fluent transition of electro-optical properties can be achieved of the inorganic part from confined 2D structures to strongly delocalized quasi-3D structures. The use of carbazole ammonium salts in 2D hybrid perovskites leads to materials for solar cells with enhanced photoconductivity and stronger resistance toward moisture yielding solar cells with enhanced stability [1]. Also, the use of pyrene ammonium salts to synthesize 2D hybrid perovskites has been explored and initial results on the structure and optoelectronic properties will be discussed [2]. In combination with the introduction of extra secondary interactions in the organic layer, a material is obtained with an exceptionally low bandgap.


[1] Multi-layered hybrid perovskites templated with carbazole derivatives: optical properties, enhanced moisture stability and solar cell characteristics. Roald Herckens, Wouter T. M. Van Gompel, Wenya Song,bc Maria C. Gelvez-Rueda, Arthur Maufort, Bart Ruttens, Jan D'Haen, Ferdinand C. Grozema, Tom Aernouts, Laurence Lutsen and Dirk Vanderzande. J. Mater. Chem. A, 2018, 6, 22899. DOI: 10.1039/c8ta08019d.

[2] Low-dimensional Hybrid Perovskites Containing an Organic Cation with an Extended Conjugated System: Tuning the Excitonic Absorption Features Wouter T.M. Van Gompel, Roald Herckens, Kristof Van Hecke, Bart Ruttens, Jan D’Haen, Laurence Lutsen and Dirk Vanderzande. ChemNanoMat 2019, 5. Accepted. DOI: 10.1002/cnma.201800561.

16:45 - 17:00
Agresti, Antonio
CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’
2D Material Engineering of Perovskite Solar Cells: the Emergence of MXenes
Antonio Agresti
CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, IT
Antonio Agresti a, Sara Pescetelli a, Hanna Pazniak b, Danina Saranin b, Daniele Rossi a, Matthias Auf der Maur a, Alessia Di Vito a, Alessandro Pecchia c, Andrea Liedl d, Rosanna Larciprete d, Aldo Di Carlo a
a, CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, Via del Politecnico, 1, Roma, IT
b, LASE–Laboratory for Advanced Solar Energy, National University of Science and Technology MISiS, Leninsky Avenue, 6, Moskva, RU
c, Consiglio Nazionale delle Ricerche-CNR, ISMN, Rome, Italy.
d, INFN-LNF - Frascati (Rome) Italy.

In the context of renewable and low cost energy production, new generation photovoltaics aims to ensure high power conversion efficiency (PCE) accomplished by low cost manufacturing processes. Perovskite solar cells (PSCs) are one of the most impressive attempt in achieving such ambitious goals. In this scenario, several device architectures and materials modifications have been proposed to tune the device interface properties and the perovskite crystal morphology. Indeed, graphene, related materials and transition metal dichalcogenide such as molybdenum disulphide (MoS2) have been successful applied in PSCs and modules [1] as interface engineering by improving the device performance [2] and by enlarging the lifetime.[3,4] Recently MXenes (MX) with the general formula Mn+1XnTx, where M represents an early  transition metal, X is carbon and/or nitrogen,  and Tx stands for surface terminations (such as OH, O, and F) came out as a new class of bidimensional (2D) materials with outstanding properties. MXenes exhibit high electronic conductivity, hydrophilic surface, high surface energy, and remarkable tunability in term of work function, ranging from 1.6eV till 6.5eV.[5] In this work, we demonstrate the use of Ti3C2Tx MX for perovskite photovoltaics by fine tuning the interface optoelectronic properties in engineered mesoscopic device. In particular, we modified the photo-electrode properties by adding MX within the precursor solutions. On one hand, transient measurements revealed the addition of MX within perovskite active layer reduces the charge trapping efficiency of deep trap states by reducing the charge accumulation and eventually the hysteresis in the current-voltage (I-V) curve. On the other hand, UPS measurements showed a shift in perovskite workfunction testifying the role of MX in modifying the perovskite electronic structure. Moreover, when ETL is modified with MX, the improvement in device PCE stems mainly from VOC and FF increase. Indeed, a reduction of charge recombination rate is demonstrated at ETL+MX/perovskite+MX interface. As further confirmation, charge carrier lifetime showed an enlarged value when MX-based ETL is used in the cell. Notably, the proposed MX-perovskite cells showed superior PCE overcoming 20% with outstanding reduction of hysteresis phenomenon. Detailed DFT calculations and device simulations permitted to define the role of MX. Due to the chemical versatility of MX, this work opens the way for a further development of perovskite technology by exploiting the possibility to optimize device structures, layers and interfaces with proper material tuning.

17:00 - 17:15
Helmbrecht, Lukas
A Bio-Inspired Route to 3D Lead-Halide Perovskites
Lukas Helmbrecht
Lukas Helmbrecht a, Hans C. Hendrikse a, Tim Holtus a, Iaroslav Baglai a, Sophie Meuret a, Gede W. P. Adhyaska a, Erik C. Garnett a, Wim L. Noorduin a
a, AMOLF, science park 104, amsterdam, 1098, NL

Strategies that offer control over the three-dimensional (3D) shape nano- and micro-scale perovskite architectures are of fundamental interest and may ultimately enable for fields ranging from optics and sensing to microelectronics and catalysis.

Here we present a route to fabricate 3D lead-halide perovskite microstructures by converting a wide range of metal carbonate structures formed by bio-inspired mineralization into lead-halide perovskite semiconductors with tunable bandgaps, while preserving the 3D shape. [1]

First, we introduce lead ions by cation exchange. Second, we use carbonate as a leaving group, facilitating anion exchange with halide, which is followed rapidly by methylammonium insertion to form the perovskite. As proof- of-principle, preprogrammed carbonate salt shapes such as vases, coral-like forms and helices are transformed into perovskites while preserving the morphology and crystallinity of the initial micro-architectures (see TOC figure).

This approach open up a novel way to create 3D perovskites by fist creating a shape and then exchanging its composition for perovskite.

17:15 - 17:30
Paetzold, Ulrich
2D/3D Perovskite Heterostructures for High Performance and High Open Circuit Voltage in Wide-Bandgap Perovskite Photovoltaics
Ulrich Paetzold
Saba Gharibzadeh a, b, Bahram Abdollahi Nejand a, b, Marius Jackoby a, Tobias Abzieher b, Somayeh Moghadamzadeh b, Jonas A. Schwenzer b, Philipp Brenner b, Raphael Schmager a, b, Amir Abbas Haghighirad c, Uli Lemmer a, b, Bryce S. Richards a, b, Ian A. Howard a, b, Ulrich W. Paetzold a, b
a, Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
b, Karlsruhe Institute of Technology (KIT), Light Technology Institute (LTI), Engesserstrasse 13, 76131 Karlsruhe, Germany
c, Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

The fast rise of organic-inorganic hybrid perovskites is based on their excellent optoelectronic material properties, combining long charge carrier lifetimes, very low non-radiative recombination rates and a high absorption coefficient. In addition, the material class of mixed-halide organic-inorganic hybrid perovskites exhibits a tunable bandgap from 1.2 - 3.1 eV, simply by adjusting the ratio of the halide precursors. This property makes these materials excellent candidates for low-cost multi-junction photovoltaics (PV). In particular, wide-bandgap perovskites (WBP) with a bandgap ranging between EG ~ 1.7 - 1.8 eV are attractive top-cell materials to improve the power conversion efficiency (PCE) of single-junction silicon or thin-film solar cells in multi-junction PV. However, obtaining high open-circuit voltage (VOC), which is a mandatory requirement to achieve sufficient PCE, is still a key challenge for WBP solar cells.

In this contribution, we report on wide-bandgap perovskite solar cells with a stable power output efficiency of up to 19.4% and a remarkable VOC of up to 1.31 V. The WBP solar cells in focus of this study employ a double-cation perovskite absorber layer based on FA and Cs in the composition FA0.83Cs0.17Pb(I0.6Br0.4)3 with a bandgap of 1.72 eV. By solution processing ammonium derivatives on top of the perovskite absorber layer, an interlayer is introduced between the bulk 3D perovskite absorber layer and the hole transport layer (spiro-OMeTAD). As we will show by means of XRD studies, this interlayer is composed of 2D Ruddlesden-Popper perovskites in intermediate phases of n = 2, resulting in a thin 2D/3D perovskite heterostructure at the hole extracting side of the solar cell. The devices with 2D/3D heterostructure achieve an enhancement in VOC of up to 80 mV, leading to a stable record VOC for WBPs (EG ~ 1.72 eV) of up to 1.31 eV. This very remarkable VOC reaches > 90% of the Shockley Queisser (SQ) limit and corresponds to one of the highest ratios of VOC-to-EG (0.76) reported for any perovskite solar cell with decent PCE. Since the relation of VOC to the SQ limit as well as the ratio VOC-to-EG serve as key figure of merits for the quality of PV absorber materials, our results highlight the very high quality of the presented 2D/3D perovskite heterostructure. Along with an improvement of the VOC, also the fill factor (FF) increased up to 78% without losing in short-circuit current density (JSC). The devices with 2D/3D perovskite heterostructure show negligible hysteresis and demonstrate very high PCE of 19.8% with corresponding stable power output efficiency of 19.4% under continuous illumination of one sun irradiation intensity and maximum power point tracking. The stable performance and high reproducibility of the perovskite solar cells employing the 2D/3D perovskite heterostructure was proven further by providing data on the statistics of > 50 devices.

Next to the material characteristics also the photophysics of the devices and 2D/3D heterostructure are studied, in order to explain the causes for the performance increase and strong enhancements in VOC. They show that the 2D/3D perovskite heterostructure at the hole extracting side of the solar cell reduces non-radiative recombination which results in a high VOC. Given the very limited conductivity of disordered 2D perovskite layers, only for an optimized 2D Ruddlesden-Popper perovskite interlayer thickness the passivation of the 2D/3D perovskite heterostructure appears in combination with fast hole extraction.

Session C1
Chair: Lioz Etgar
14:30 - 14:45
Correa, Luiza
CSEM Brasil
Electron Transport Material Modification for High-efficiency and Stable Flexible P3HT:O-IDTBR Polymer Solar Cells Blade Coated in Air from Non-halogenated Solvents
Luiza Correa
CSEM Brasil, BR
Luiza de Queiroz Correa a, Juliana Luiza da Silva Martins a, Gabriela de Amorim Soares a, Barbara Hellen de Souza Miranda a, Diego Bagnis a
a, CSEM Brasil, Avenida José Cândido da Silveira, 2000, Belo Horizonte, BR

The recent rise of non-fullerene (NF) acceptor molecules has taken P3HT polymer donor (poly(3-hexylthiophene)) to a next level in the field of organic solar cells. Despite of its competitive price compared to other semiconductor polymers, the bulk heterojunction of P3HT combined with the standard fullerene acceptor [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) has shown low power conversion efficiencies and burn-in under light exposure. For these reasons, P3HT-based devices had limited commercial application for years. However, the rapid development of the NF molecules and the launch of O-IDTBR (rhodanine-benzothiadiazole-coupled indacenodithiophene) [1] a few years ago enabled to think of P3HT as a feasible material to be used in production once this system can combine reasonable efficiency, stability and low cost.

In this work, we present results of 6.0% efficiency in a lab-scale of all solution-processed devices on flexible substrates (AA 0.55 cm2) from environmentally friendly solvents. The cells were fabricated in air by the scalable method of blade coating. The interlayers used are zinc oxide (ZnO) as electron transport material (ETM) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) as hole transport material (HTM). The bottom electrode is the IMI, a triple layer of a silver alloy sandwiched by Indium tin oxide (ITO) layers coated on top of the PET-based substrate. The top electrode is the Silver (Ag) deposited by thermal vacuum evaporation.  The inverted device structure is as follows: PET/IMI/ZnO/P3HT:O-IDTBR/PEDOT:PSS/Ag. [2]

We show as well how an ETM modification made by the introduction of a polymer additive in the inorganic ZnO layer played a key role on the stability of devices. This solution shows to be necessary to reduce in a drastic way the drop in performance after standard encapsulation with flexible barriers and enhance the photo-stability. The usual loss in performance that has been observed with the pure ZnO-based devices is connected to the large increase in series resistance (Rs) after encapsulation. The additive concentration was tested from 1 up to 5% in weight and the impact in efficiency and stability were investigated in order to find the optimized recipe and the right additive content. Both solutions of the modificated ETM and the active layer based in green solvents were successfully applied on the roll-to-roll (R2R) R&D pilot machine leading to stable encapsulated large-area modules (AA 21.6cm2) of over 4.0% efficiencies.

14:45 - 15:00
Barulina, Elena
Aix-Marseille University, Centre Interdisciplinaire de Nanosciences de Marseille CINaM, UMR CNRS 7325, Marseille, France
A Detailed Stability Study of Highly Efficient Polymer Solar Cells Based on ITIC Derivatives
Elena Barulina
Aix-Marseille University, Centre Interdisciplinaire de Nanosciences de Marseille CINaM, UMR CNRS 7325, Marseille, France, FR
Elena Barulina a, b, Pavlo Perkhun a, Wolfgang Köntges c, Martin Pfannmöller c, Sadok Ben Dkhil b, Jean-Jacques Simon d, Olivier Margeat a, Christine Videlot-Ackermann a, Jörg Ackermann a
a, Aix-Marseille Univ., UMR CNRS 7325, Centre Interdisciplinaire de Nanosciences de Marseille (CINaM), 13009 Marseille Cedex 09, France
b, Dracula Technologies, 4 rue Georges Auric, 26000 Valence, France
c, Centre for Advanced Materials (CAM), Heidelberg University, Heidelberg, Germany
d, Aix-Marseille Univ., Univ. Toulon, UMR CNRS 7334, Institut Matériaux Microélectronique Nanoscience de Provence (IM2NP), Marseille, France

   Today, organic solar cells are alternative energy sources, which are now competitive for an introduction into a new generation photovoltaic market due to their high performance, processing on a large surface, flexibility and low price. There has been considerable research that allowed very recently to achieve certified power conversion efficiency over 17% in a tandem organic solar cells [1]. This tremendous increase for organic photovoltaics during the last two years was enabled by the development of novel non-fullerene acceptor (NFA) materials that outperform fullerene-based acceptors. However, the long-term stability of these new photovoltaic materials and the corresponding devices is a key factor to figure out the commercial viability and must be addressed in detail.

   While some works on new NFAs mentioned improved stability of NFA based solar cells under specific conditions (storage in air or under LED light soaking), the work of Brabec and coll. [2] has very recently provided a study dedicated to one of the most important new NFA family, namely the ITIC derivatives (ITIC, ITIC-4F, ITIC-M, ITIC-DM, ITIC-Th) indicating the fluorinated acceptor are most stable. However, the stability of the solar cells was only studied under LED light, while standard tests such as ISOS-D-2 High-temperature storage as well as ISOS-L-1 (Laboratory weathering under continuous illumination at AM 1.5) [3] were missing.

   Previously, we investigated the stability of solar cells based on PTB7 and fullerene derivatives depending on interfacial layers [4], [5] and thermal treatments. The aim of this work is to study in detail the stability of high efficiency organic solar cells using different ITIC derivatives by applying the three standard tests and compare the degradation processes of NFA based solar cells under illumination at AM 1.5 and LED.  Furthermore, in order to compare the NFA to fullerene acceptors, we developed a PCE10:PC70BM blend system that is fully stable [6] under ISOS-L-1 conditions. This demonstrates the stability of our device structure including interfacial layers and allows to evaluate the NFA related degradation processes in the corresponding solar cells. The stabilized PCE-10:PC70BM solar cells are compared to PCE-12:ITIC, PBDBT-F:ITIC-4F, Furthermore, detailed characterizations of the device degradation in relation to the morphology will be discussed using atomic force microscopy and spectral imaging analyses from analytical scanning transmission electron microscopy. Whilst PCE-10:PC70BM solar cells are found to be stable with an efficiency of 7%, we show that both ITIC:PCE-12 and ITIC-4F:PBDBT-F solar cells with performances of 10% and 11%, respectively, degrade very fast under simulated AM 1.5 illumination. LED light clearly reduced device degradation. We also discuss thermal treatment techniques aiming to improve the stability of ITIC based solar cells by improving the crystallinity of the polymer blend.

Figure 1 The stability of encapsulated device under continuous illumination at 1.5 AM lamp in an air

15:00 - 15:15
Pfannmöller, Martin
Centre for Advanced Materials (CAM), Heidelberg University, Heidelberg, Germany
Visualizing the Surface Morphology of Non-fullerene Acceptor Blends by Automated segmentation of Spatially Resolved Electron Spectra from Ultra-low Voltage Scanning Electron Microscopy
Martin Pfannmöller
Centre for Advanced Materials (CAM), Heidelberg University, Heidelberg, Germany
Jochen Kammerer a, Rasmus Schröder a, b, Irene Wacker a, b, Riva Alkarsifi c, Pavlo Perkhun c, Christine Videlot-Ackermann c, Olivier Margeat c, Jörg Ackermann c, Martin Pfannmöller a
a, Centre for Advanced Materials (CAM), Heidelberg University, Heidelberg, Germany
b, Cryo Electron Microscopy, BioQuant, Heidelberg University Hospital, Heidelberg, Germany
c, CINaM, CNRS, Aix Marseille University, Marseille, France

Significant advances were recently made in achieving high efficiency organic photovoltaic cells based on non-fullerene acceptors (NFA) [1, 2]. The morphology of bulk heterojunctions (BHJ) is one of the key parameters determining their efficiency. However, optimization still relies primarily on trial and error and personal experience rather than on profound knowledge of the evolving morphology. The similar atomic composition and structures of the donor and acceptor molecules necessitate the use of advanced spatially resolved spectroscopy to identify the different phases at the nanoscale [3]. This is particularly valid for polymer:NFA blends, which show considerable higher similarity in their electronic spectral fingerprint, as compared to polymer:fullerene systems. Deeper knowledge of the morphology and of developing material phases will not only improve the optimization process of the cells [4], they are also crucial for understanding fundamental physical processes at the interfaces within NFA based BHJs. This information may also explain observations, where the absence of a significant driving force for charge separation at the donor/acceptor interface is in the center of an ongoing debate [5].

We demonstrate a novel technique to visualize the surface morphology of organic photovoltaic blends at the nanoscale. We use spatially resolved electron spectroscopy in a prototype aberration corrected ultra-low voltage scanning electron microscope (ULVSEM), the DELTA (Carl Zeiss Microscopy, Germany) [6]. The main advantage of ULVSEM is the extremely low electron landing energy down to 20 eV instead of ≥1 keV in standard SEM and 30 – 300 keV in TEM. Firstly, the interaction volume between electron probe and sample at such low primary energy is drastically reduced – only the first few nanometers below the surface are imaged. Thus, signal mixing at interfaces is minimized (cf. Figure 1a). Secondly, we observe minimal beam damage for organic materials in this ultra-low voltage regime.

In contrast to previous attempts with spectroscopy in SEM [7], we do not compare spectra of the pure components to identify spectrometer settings to maximize contrast between donor and acceptor materials. Instead, our method relies on nano-resolved spectra and is therefore sensitive towards local variations in the electronic structure of the investigated sample. Unsupervised machine learning algorithms are used to reveal spectroscopic similarities within the datasets. This unbiased procedure yields three phases in a PTB7:PC70BM model system investigated at 50 eV primary energy. The phases can be assigned to a polymer rich, a fullerene rich and a mixed phase. Smaller domain structures are observed in comparison to results from analytical transmission electron microscope (ATEM) reference measurements based on the methodology proposed in previous works [8]. The procedure and resulting morphology data are illustrated in Figure 1b,c.

We expect that combined analyses of lateral and cross-sectional surfaces will shed light on the processes at inter-layer as well as donor:acceptor interfaces for an enhanced understanding of charge separation processes.

15:15 - 15:30
Polino, Giuseppina
CHOSE- Dept. of Electronics Engineering-University of Rome
Fully Spray-Coated Organic Photovoltaic Cells with Green Solvents: Study of Interfaces and Scale-Up
Giuseppina Polino
CHOSE- Dept. of Electronics Engineering-University of Rome
Giuseppina Polino a, Luca La Notte a, Simone Dell'Elce b, Andrea Liscio b, c, Giorgio Cardone d, Babak Taheri a, Aldo Di Carlo a, Andrea Reale a, Francesca Brunetti a
a, CHOSE- Centre for Hybrid and Organic Solar Energy, University of Rome “Tor Vergata”, Electronic Engineering Department, Via Giacomo Peroni 400, Rome, 131, IT
b, Istituto per la Sintesi e la Fotoreattivita` CNR, via Gobetti 101, Bologna, 40120, IT
c, Istituto dei sistemi complessi CNR
d, PPG Italy Business Support SRL

The introduction of low-band-gap polymer donors in organic bulk heterojunction solar cells allowed to achieve high power conversion efficiency (PCE) [1]. Such optimal performance are strongly correlated to the use of spin coating as technique to ensure reproducible and homogeneous films and chlorinated solvents that help the suitable nanoscale morphology. But this procedure is not industry compatible since spin coating does not allow large scale production and chlorinated solvents are poorly tolerated in workplaces since they are harmful towards environment and human health [2,3]. For this reason, we realized high-performing inverted polymer solar cells by depositing all the layers through a scalable technique as spray coating [4] by using green solvents. We investigated the morphology at the interface between photoactive layer (PAL) deposited through a non-chlorinated solvent (ortho-xylene) and hole and electron transport layers processed from alcohol based solvents, via atomic force microscopy (AFM). In particular, we analyzed the interface between PAL and an electron transport layer (ETL) fabricated using zinc oxide nanoparticles coated with polyethylenimine ethoxylated (PEIE) [5]. Then, we studied the interface between PAL and three different combination of  hole transport layer (HTL)/anode: i) a mixture of two commercial poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) formulations (CPP:PH1000), ii)  an anhydrous PEDOT:PSS (A-PEDOT) dispersion developed in our laboratory, iii) a double layer composed of vanadium (V) oxide (V2O5) and PH1000 electrode. Finally, we evaluated the electrical performance of small area devices (10 mm2) realized using the three typologies of HTL/Anode interfaces, obtaining comparable results in terms of PCE in the case of V2O5/PH1000 (3.25%) and anhydrous PEDOT:PSS (3.6%) when the devices were illuminated from ITO side. By illuminating from the PEDOT side, the PCE decreased of 26% in the case of V2O5/PH1000 and was halved in the case of A-PEDOT. Therefore, we decide to fabricate and electrically characterize organic photovoltaic modules (active area: 13 cm2) with ITO/ZnO-PEIE/PTB7:PC70BM/V2O5/PH1000 structure, by demonstrating the successful application of spray coating for scale-up of Organic Photovoltaics.

15:30 - 15:45
Schiller, Andreas
Institute of Computational Physics, Zurich University of Applied Sciences
Accumulation of ionic charge carriers and the influence of steric potential in perovskite solar cells
Andreas Schiller
Institute of Computational Physics, Zurich University of Applied Sciences, CH
Andreas Schiller a, b, Balthasar Blülle b, Christoph Kirsch a, Martin Neukom a, b, Beat Ruhstaller a, b
a, Institute of Computational Physics, Zurich University of Applied Sciences (ZHAW), 8401 Winterthur (Switzerland)
b, Fluxim AG, Katharina-Sulzer-Platz, 2, Winterthur, CH

Modeling perovskite cells with the drift-diffusion approach including both electronic and ionic charge carriers can qualitatively reproduce several characteristic measurement results including IV curve hysteresis [1,2], dark current decay transients [3] and negative capacitance [4]. Up to now, however, no parameter set has been published which quantitatively matches multiple experiments. This raises the question, whether and how the model needs to be extended or adapted further.

The commonly used drift-diffusion approach makes use of the Boltzmann statistics for both electronic and ionic charge carriers. This model typically leads to a strong accumulation of ionic charge carriers at layer interfaces and thus a very fine space discretization is required in order to achieve numerical results of sufficient precision. More importantly, the exceedingly high ion density close to interfaces contradicts the physical understanding of ions as particles or vacancies with a certain volume requirement. S. van Reenen et al [5] described this behavior for OLECs but they circumvented the problem of strong accumulation by using a coarse space discretization.

We propose to model the interaction among ionic charge carriers as a purely geometrical effect. The steric potential derived in that way leads to a Fermi-like model [6], which effectively takes into account the limited amount of available states for ions in a given volume.

In this presentation, we shall discuss the suggested model and its implementation for both, steady-state and transient drift-diffusion simulations. In a detailed case study for a Methyl Ammonium Lead Iodide (MAPI) perovskite solar cell, we investigate the influence of the steric potential on the charge carrier profiles and we discuss the impact of the charge carrier statistics on the device properties of a solar cell.

The proper understanding of ion accumulation at the interfaces of perovskite devices will be a significant step towards the description of the full steady-state and dynamic device characteristics by a single set of parameters.

15:45 - 16:00
Daiber, Benjamin
Efficiency Potential of Singlet Fission Enhanced Silicon Solar Cells using Different Energy Transfer Schemes
Benjamin Daiber
Benjamin Daiber a, Koen v.d. Hoven a, Moritz H. Futscher a, Bruno Ehrler a
a, Center for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands

Silicon is the dominating solar cell material, therefore add-ons on the silicon solar cell that can improve the power conversion efficiency are urgently needed. In certain organic materials singlet fission generates two triplet (spin 1) excitons from one singlet (spin 0) exciton. If the triplet excitons are harvested in the silicon solar cell the efficiency could be dramatically increased, as we show. There are different transfer pathways between the organic singlet fission material and silicon. We have simulated the achievable efficiency for each transfer path with realistic assumptions such as a singlet fission quantum efficiency of 1.7 (1.7 e-h pairs per high energy photon), a transmission loss of 5%, and a 50 meV Stokes shift in case of optical transmission.

Even with these realistic assumptions, the efficiency of a silicon/singlet fission solar cell can be as high as 34% when combined with the current record silicon solar cell of 27%. We found that dissociating the triplet excitons at the interface leads to a large potential efficiency gain because a triplet energy lower than the silicon bandgap still leads to charge generation, and allows for high current generation. We also find that current singlet fission materials do not absorb light strongly enough, motivating sensitization schemes. Finally, we compare the singlet fission/silicon solar cells to the efficiency potential of perovskite/silicon tandem solar cells. We find that tandem cells are particularly beneficial for a silicon base cell with low efficiency, while a highly efficient silicon solar cells benefits less from the perovskite top cell. In contrast, the efficiency gain from the singlet fission layer is almost constant for all silicon base cells, and for highly efficient silicon cells would clearly outperform a high-efficiency perovskite top cell.

16:00 - 16:30
Coffee Break
16:30 - 17:00
Ehrler, Bruno
Institute AMOLF
The Path towards Efficient and Stable Perovskite/Silicon Tandem Solar Cells
Bruno Ehrler
Institute AMOLF

Bruno Ehrler is currently heading the Hybrid Solar Cells group at AMOLF since 2014, focusing on organic small molecules undergoing singlet fission, quantum dots and perovskites. Before moving to Amsterdam, he was a research fellow in the Optoelectronics Group at Cambridge University following post-doctoral work with Professor Sir Richard Friend. He obtained his PhD from the University of Cambridge under the supervision of Professor Neil Greenham.

Bruno Ehrler a, Moritz Futscher a, Lucie McGovern a
a, Center for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands

Perovskite/silicon tandem solar cells appear to be the implementation with the highest efficiency potential in the short term. For successful implementation these cells need to be both efficient and stable.

In most cases, the efficiency of these cells is tested in the laboratory under standard test conditions. However, in real weather conditions the performance may vary because of a changing solar spectrum, temperature, and light intensity. We model the efficiency of perovskite/silicon tandem solar cells under real world conditions. We show that the two-terminal implementation is sensitive to spectral changes, but that also the four terminal configuration is sensitive to climate conditions, in particular low-intensity light. We use the model to determine how perovskite cells have to improve to minimize the losses of tandem cells in realistic conditions. We show that the largest potential comes from reducing non-radiative recombination.

Non-radiative recombination has been linked to the density and distribution of mobile ions in these perovskites. Thus, understanding and controlling ion migration is critical for highest-performance perovskite solar cells. In addition, ion migration is also linked to long-term degradation of perovskite solar cells. In the second part of my talk I will summarize our work on ion migration in MAPbI3 and other perovskite compositions. We use transient ion-drift, a capacitance-based technique, to extract the activation energy, mobile ion density, diffusion coefficient, and charge, of each mobile ion species. I will discuss the influence of degradation, fabrication and composition on ion migration.

A complete understanding of mobile ions in perovskite materials and devices will allow us to control the migration, and thereby minimize both non-radiative recombination and degradation, critical for the success of perovskite/silicon tandem solar cells.

17:00 - 17:15
Borchert, Juliane
University of Oxford
Impurities and Their Influence on the Co-evaporation of Methylammonium Perovskite Thin-film Solar Cells
Juliane Borchert
University of Oxford, GB
Juliane Bochert a, Ievgen Levchuk b, Lavina C. Snoek a, Mathias Uller Rothmann a, Henry J. Snaith a, Christoph J. Brabec b, Laura M. Herz a, Michael B. Johnston a
a, Clarendon Laboratory, Department of Physics, Oxford University, Oxford OX1 3PU, UK
b, Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander Universität Erlangen-Nürnberg, Martensstr. 7, 91058 Erlangen, Germany

In recent years power conversion efficiencies for lab-scale metal halide perovskite solar cells have risen rapidly to over 23.7% [1]. These perovskite semiconductors are advantageous due to their low Shockley-Read-Hall recombination rates, high absorption coefficients across much of the solar spectrum and high charge-carrier diffusion lengths and mobilities [2]. The planar heterojunction solar cell is a simple and popular design with the first efficient perovskite solar cell of this architecture fabricated by co-evaporation of lead iodide and methylammonium iodide (MAI) [3]. Co-evaporation of perovskite thin-films is carried out in a vacuum chamber in which two or more precursors are heated simultaneously until they evaporate. The vapours rise up and condense on the substrate which is mounted above on a rotating sample holder. Co-evaporation is a scalable process which is already used in a number of other industries and films grown via co-evaporation are uniform, have no pin-holes and are smooth over large areas [4]. This process is also solvent free which makes it fully additive and avoids the washing off of underlying layers. This is especially useful when complex layer stacks are being fabricated, for example in tandem solar cells.

An important factor that will influence the commercial success of metal halide perovskite solar cells is the scalability of the deposition processes. To be able to scale a process, the reproducibility and yield of that process are both critical. In the past, several groups have encountered challenges with the evaporation of methylammonium iodide, including a variability of the chamber pressure and problems with the rate control of MAI deposition. The established method for the control of thermal evaporation processes, such as co-evaporation, is the use of quartz micro balances (QMBs). Unfortunately, it has frequently been reported, that these do not yield reliable results when used to monitor MAI evaporation. To resolve some of these challenges, we studied the role of impurities during the co-evaporation and their influence on the control of the evaporation process. To do this, we first characterised the precursor itself using nuclear magnetic resonance (NMR) and mass spectroscopy. We then evaporated perovskite films and monitored the evaporation process using quartz micro balances which are the established approach for rate control in thin-film deposition. Additionally we employed a residual gas analysis system to perform mass spectroscopy of the gas in the vacuum chamber during the evaporation. After the evaporation we characterised the deposited thin-films using a variety of methods, including scanning electron microscopy and X-ray diffraction. Finally we fabricated solar cells using MAI of different purity and measured their power conversion efficiency. Using this approach we are able to shed light on the influence of impurities in MAI on the co-evaporation of methylammonium lead iodide and the final solar cell performance. We are furthermore able to make suggestions on how to improve the control of the MAI evaporation and therefore the control over and reproducibility of the co-evaporation of methylammonium lead iodide thin-films.

17:15 - 17:30
Abdi Jalebi, Mojtaba
University of Cambridge - UK
Highly Luminescent and Stable Metal Halide Perovskite Devices via Graded Hole Transport Layers
Mojtaba Abdi Jalebi
University of Cambridge - UK, GB
Mojtaba Abdi-Jalebi a, M. Ibrahim Dar b, Satyaprasad P. Senanayak a, Henning Sirringhaus a, Michael Grätzel b, Richard H. Friend a
a, Cavendish Laboratory, Department of Physics, University of Cambridge, UK, JJ Thomson Avenue, Cambridge, GB
b, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, Station 6, CH-1015 Lausanne, Lausanne, CH

Despite rapid improvements in power conversion efficiency (PCE) over the past few years, the long-term stability of perovskite solar cells (PSCs) remains a pressing challenge that hinders their commercialisation. One source of instability in these devices is interfacial defects, in particular, those that exist between the perovskite and the hole transport layer (HTL). Here, we demonstrate that thermally evaporated dopant-free tetracene on top of the perovskite layer, capped with a doped Spiro-OMeTAD layer and top gold electrode offers an excellent hole-extracting stack with minimal interfacial defect levels.  However, we and others find that dopant-free organic semiconductor HTLs introduce undesirable injection barriers to the metal electrode. By capping 120 nm of tetracene with 200 nm solution-processed lithium TFSI - doped Spiro-OMeTAD, we demonstrate a graded hole injection interface to the top gold layer with enhanced ohmic extraction. For a perovskite layer interfaced between this graded HTLs structure and a mesoporous TiO2 electron-extracting layer its external photoluminescence yield reaches 15%, compared to 5% for the perovskite layer interfaced between TiO2 and Spiro-OMeTAD alone. For complete solar cell devices containing tetracene/Spiro-OMeTAD as the HTL with graded doping profile, we demonstrate PCEs of up to 21.5% and extended power output over 550 hours continuous illumination at AM1.5 retaining more than 90% of the initial performance, validating our approach. Our findings represent a breakthrough in the construction of stable PSCs with minimized non-radiative losses.

17:30 - 19:00
Poster Session
Tue May 14 2019
08:55 - 09:00
Announcement of the day
Session G2.1
Chair: Filippo De Angelis
09:00 - 09:45
Kanatzidis, Mercouri
Northwestern University
Chemistry and Devices from Low Dimensional Halide Perovskites Semiconductors
Mercouri Kanatzidis
Northwestern University, US
Professor MERCOURI G. KANATZIDIS Charles E. and Emma H. Morrison Chair Department of Chemistry, Northwestern University, Evanston, IL 60208 Tel. (847)-467-1541, FAX (847)-491-7713 EDUCATION AND TRAINING B.S. Chemistry, November 1979, Aristotle University of Thessaloniki Ph.D. Chemistry, 1984, University of Iowa, Postdoctoral Associate, 1985, University of Michigan Postdoctoral Associate, 1987, Northwestern University RESEARCH AND PROFESSIONAL EXPERIENCE 8/06- present: Professor of Chemistry, Northwestern University (joint appointment with Argonne National Laboratory). 6/93-7/06: Professor of Chemistry, Michigan State University. 7/91-6/93: Associate Professor, Michigan State University. 7/87-6/91: Assistant Professor, Michigan State University. Awards and honors: Presidential Young Investigator Award. National Science Foundation, 1989-1994. ACS Inorganic Chemistry Div. Award: EXXON Faculty Fellowship in Solid State Chemistry, 1990. Beckman Young Investigator, 1992-1994. Alfred P. Sloan Fellow 1991-1993. Camille and Henry Dreyfus Teacher Scholar 1993-1998. Michigan State University Distinguished Professor 1998. Sigma Xi Senior Meritorious Faculty Award 2000. University Distinguished Professor MSU 2001. John Simon Guggenheim Foundation Fellow 2002. Alexander von Humboldt Prize, 2003. Morley Medal, American Chemical Society, Cleveland Section, 2003. Charles E. and Emma H. Morrison Professor Northwestern University 2006. Materials Research Society Fellow 2010. American Association for the Advancement of Science Fellow 2012. Chetham Lecturer Award, University of California Santa Barbara, 2013. Einstein Professor Chinese Academy of Sciences 2014. International Thermoelectric Society Outstanding Achievement Award 2014. PROFESSIONAL SERVICE AND RECOGNITION Chair-Elect Solid State Subdivision, Division of Inorganic Chemistry, ACS, 1997-1998. Editorial Advisory Board Chemistry of Materials, 1993-2000. Editorial Advisory Board Inorganic Chemistry 1994-1997. Editorial Advisory Board Journal of Alloys and Compounds 1996-2012. Editorial Advisory Board Energy and Environmental Science 2012-present. Editor-in-Chief: Journal of Solid State Chemistry. Chairman Solid State Chemistry Subdivision, American Chemical Soc 1998-1999. American Chemical Society, Div. of Chemical Education, Examinations Institute: 1996 and 2003 Inorganic Chemistry Committee, DOE Review Panelist 2004, 2007, 2010, 2012 NSF Panelist 2006, 2008, 2010, 2011, 2012. PUBLICATIONS (Publications >800, citations >26,000, H index 80) Total number of graduate students graduated: 47 Total number of postdocs advised: 75 Ten female group-alumnae hold faculty positions in American and foreign universities. Graduate Advisor: Dimitri Coucouvanis, (U. Michigan) Postdoctoral Advisor: Tobin J. Marks (Northwestern University)
Mercouri Kanatzidis a
a, Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.

Two-dimensional (2D) metal halide perovskites have made an impressive entry in the field of solar cells and LEDs as highly promising semiconductors. They feature a high degree of structural flexibility and tunable optoelectronic properties. They have a general formula of (A’)2(A)n-1MnX3n+1, where A = Cs+, CH3NH3+ (MA), HC(NH2)2+ (FA), M = Ge2+, Sn2+, Pb2+ and X = Cl-, Br-, I-, are the perovskite components and A’+ = RNH3 is an organic spacer. There are four kinds of 2D organic inorganic hybrid perovskites so far: Ruddelsden-Popper, Cation-ordered, Jacobson-Dion and Diammonium Cation. These vary from one another in ways the inorganic slabs stack and the way the spacer cations interact with the inorganic slabs. Generally, 2D perovskites form from solution via the bottom-up self-assembly of individual, semiconducting perovskite sheets having an adjustable slab thickness of up to few nanometers, separated by insulating bulky organic molecules. As a result, they behave as natural multiple quantum wells (QWs) with the semiconducting perovskite layers representing the wells and the insulating organic spacers representing the barriers. The width of the barrier is fixed and depends only on the length of the A’ cation, while the width of the well can be adjusted by varying the thickness of perovskite slabs, which is defined by the n variable in (A’)2(A)n-1MnX3n+1. It is critical to understand the thermodynamic and chemical limitations of the maximum layer thickness that can be sandwiched between the organic bilayers while retaining the structural integrity of the 2D perovskite.


09:45 - 10:15
Ginsberg, Naomi
University of California, Berkeley, US
Resolving Carrier Dynamics in Metal Halide Perovskites to Elucidate Structural Transformation Mechanisms and the Impact of Structural Heterogeneity on Transport
Naomi Ginsberg
University of California, Berkeley, US
Naomi Ginsberg a, b, Milan Delor b, Connor Bischak b, Minliang Lai b, Hannah Weaver a, Dylan Lu b, QinQin Yu a, Peidong Yang b, David Limmer b
a, Department of Physics, University of California, Berkeley, USA
b, Department of Chemistry, University of California, Berkeley, USA

The intrinsic physical properties of metal halide perovskites, such as electron-phonon coupling, combined with the inhomogeneities that result from many solution-based thin film deposition processes, motivate a strong emphasis on characterization approaches that elucidate the complex and fascinating relationships between material structure and function across multiple relevant scales. We therefore describe lessons from a spectrum of dynamic imaging measurements that address this important need. First, we show how our development of time-resolved elastic scattering microscopy—with a nanoscale sensitivity—allows us to elucidate how grain boundaries impact charge carrier migration through their lateral- and depth-dependent resistivities in a variety of thin films. While this approach may also be used to detect photoinduced demixing in mixed halide perovskites, we demonstrate the way in which A-cation selection enables the tuning of the extent of demixing at high spatial resolution via cathodoluminescence microscopy. This second approach furthermore facilitates a quantitative mechanistic analysis of the activation energy in the structural phase transition in inorganic lead halide nanostructures. We determine that the conversion from non-perovskite to perovskite phases requires only the energy required to break lead-halide bonds, requiring a disordered region between phases that suggests that the perovskite phase grows above the transition temperature from a nanoscale melt. Correlating the electronic and optical properties with structural ones at the nanoscale with these powerful dynamic imaging approaches provides highly complementary insight into the many enigmatic properties of metal halide perovskites that will need to be addressed to fully develop them into widely adopted photovoltaics.

10:15 - 10:45
Padture, Nitin
Brown University
Nano-/Micro-structural Tailoring of Pb-based and Pb-free Multi-dimensional Halide Perovskites for Scalable, Efficient, and Stable Solar Cells
Nitin Padture
Brown University
Nitin Padture a
a, Brown University, 184 Hope Street, Box D, Providence, RI 02912

Thin-film perovskite solar cells (PSCs), where the record efficiency has rocketed from under 4% to near 24% in just nine years, offer unprecedented promise of low-cost, high-efficiency renewable electricity generation. Organic-inorganic halide perovskites (OIHPs) at the heart of PSCs have unique structures with desirable optical and electronic properties. To exploit these properties for PSCs application, the reliable deposition of high-quality OIHP thin films over large areas is critically important. The microstructures and grain-boundary networks in the resulting polycrystalline OIHP thin films are equally important as they control the PSC performance and stability. Fundamental phenomena pertaining to synthesis, crystallization, coarsening, microstructural evolution, and grain-boundary functionalization involved in the processing of OIHP thin films for PSCs will be discussed with specific examples. In addition, the discovery of three new Pb-free halide perovskites (3D Ti-based and Sn-Ge-based all-inorganic; and low-dimensional organic-inorganic), together with the demonstration of viable PSCs based on these new materials, will be presented. Furthermore, the unique ion-diffusion resistance and mechanical behavior of the latter halide perovskites will be discussed. The overall goal of our research is to have deterministic control over the scalable processing of tailored halide perovskite thin films with desired compositions, phases, dimensionalities, microstructures, and grain-boundary networks for scalable, efficient, and stable PSCs.

10:45 - 11:15
Coffee Break
Session G2.2
Chair: Mercouri Kanatzidis
11:15 - 11:45
Etgar, Lioz
The Hebrew University of Jerusalem
Low Dimensional Perovskite: Stability, Solar Cells and Nanostructures
Lioz Etgar
The Hebrew University of Jerusalem, IL

Lioz Etgar obtained his Ph.D. (2009) at the Technion–Israel Institute of Technology and completed post-doctoral research with Prof. Michael Grätzel at EPFL, Switzerland.  In his post-doctoral research, he received a Marie Curie Fellowship and won the Wolf Prize for young scientists. Since 2012, he has been a senior lecturer in the Institute of Chemistry at the Hebrew University. On 2017 he received an Associate Professor position. Prof. Etgar was the first to demonstrate the possibility to work with the perovskite as light harvester and hole conductor in the solar cell which result in one of the pioneer publication in this field. Recently Prof. Etgar won the prestigious Krill prize by the Wolf foundation. Etgar’s research group focuses on the development of innovative solar cells. Prof. Etgar is researching new excitonic solar cells structures/architectures while designing and controlling the inorganic light harvester structure and properties to improve the photovoltaic parameters.

Lioz Etgar a
a, Institute of Chemistry, Hebrew University of Jerusalem, Givat Ram, david simony 34, Jerusalem, IL

Perovskite is a promising light harvester for use in photovoltaic solar cells. In recent

years, the power conversion efficiency of perovskite solar cells has been dramatically

increased, making them a competitive source of renewable energy.

This work will discusses new directions related to organic inorganic perovskite and their applications in solar cells.

In low dimensional systems, stability of excitons in quantum wells is greatly enhanced due to the confined effect and the coulomb interaction. The exciton binding energy of the typical 2D organic-inorganic perovskites is up to 300 meV and their self-assembled films exhibit bright photoluminescence at room temperature.

In this work we will show the dimensionality in the perovskite structure. The 2D perovskite structure should provide stable perovskite structure compare to the 3D structure. The additional long organic cation, which is added to the perovskite structure (in the 2D structure), is expected to provide hydrophobicity, which will enhance the resistivity of the perovskite to humidity. Moreover, we will demonstrate the use of 2D perovskite in high efficiency solar cells.

In addition, we will show that the black phase of cesium lead iodide can be stabilized when the perovskite dimensionality is reduced. X-ray diffraction, absorbance, and scanning electron microscopy were used to follow the degradation process of various dimensionalities under room conditions and 1 sun illumination.

Organic-inorganic halide perovskite is used mainly in its “bulk” form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this part, we will present our recent progress related to the synthesis and characterization of perovskite NPs- i.e. Inorganic and hybrid organic-inorganic NPs. New nanostructures such us: NRs and NWs will be presented and the introduction of other cations such us Rb will be shown.

11:45 - 12:15
Manna, Liberato
Istituto Italiano di Tecnologia
Halide Perovskite Nanocrystals: Their Synthesis, Chemical, Structural, and Surface Transformations
Liberato Manna
Istituto Italiano di Tecnologia, IT

Bio Professional Preparation M.S. in Chemistry, with Honours, University of Bari, Italy, 1996 Ph.D. in Chemistry, University of Bari, Italy, 2001 Research interests Prof. L. Manna is an expert of synthesis and assembly of colloidal nanocrystals. His research interests span the advanced synthesis, structural characterization and assembly of inorganic nanostructures for applications in energy-related areas, in photonics, electronics and biology.

Liberato Manna a
a, Istituto Italiano di Tecnologia (IIT), Genova, Italy, Via Morego, 30, Genova, IT

Halide perovskite semiconductors can merge the highly efficient operational principles of conventional inorganic semiconductors with the low‑temperature solution processability of emerging organic and hybrid materials, offering a promising route towards cheaply generating electricity as well as light. Perovskites not only show exceptional primary optoelectronic properties such as a direct bandgap, small exciton binding energy, low carrier recombination rates, ambipolar transport, and tunability of the bandgap covering a wavelength range from the near‑infrared to the ultraviolet, but they are also very attractive for their ease of processability for mass production (e.g. printing from solution) and for the large availability of their chemical components. Following a surge of interest in this class of materials, research on halide perovskite nanocrystals as well has gathered momentum in the last years. In such a narrow time span, several properties/features of halide perovskite nanocrystals were investigated, among them electroluminescence, lasing, anion-exchange, as well as control of size and shape such that nanocrystals in the quantum confinement regime were recently reported. Important developments include doping, synthesis of Pb-free perovskite nanocrystals, and investigations of their rich surface chemistry. The present talk will highlight the research activities of our group on halide perovskite and perovskite-related nanocrystals, with emphasis on synthesis, as well as structural, chemical, and surface transformations.

12:15 - 12:45
Bakr, Osman
Nanoscale and Bulk Perovskite Single-Crystals: Surface Engineering for Efficient LEDs, Photodetectors, and Solar Cells
Osman Bakr
Osman M. Bakr a
a, King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal, SA

In colloidal nanocrystal form, lead halide perovskites possess high photoluminescence quantum yields, while in bulk single-crystal form they exhibit long charge-carrier diffusion lengths. However, without proper strategies to diminish crystal surface defects and manage surface quality, the desired characteristics of perovskites cannot be effectively exploited for photovoltaic and optoelectronic devices. Here I discuss novel strategies to passivate the surface defects and improve the surface quality of perovskite nanocrystals and bulk single-crystals, enabling the fabrication of efficient devices. We demonstrate the passivation of CsPbX3-type nanocrystals with molecular ligands and metal dopants leading to stable near-unity quantum yield emitters, as well as efficient blue and red light-emitting diodes (LEDs). We also show the importance of designing crystal growth conditions, such as solvent, temperature, and substrate in order to grow bulk single-crystals with low-defect densities and good surface quality. Depending on the composition, MAPbX3-type single crystals grown (tens of microns thick) under optimal conditions were used to realize: a) very sensitive visible-blind UV-photodetectors with nanosecond response time; and b) single-crystal solar cells with ~21% power conversion efficiency. Unlike thin film polycrystalline solar cells, efficient cells with a grain-free single-crystal absorber are an ideal unobstructed system for investigating the device physics and chemistry of perovskites.

12:45 - 13:15
Case, Christopher
Oxford PV
From PERC to passivated contacts to perovskite: the path to increasing efficiency
Christopher Case
Oxford PV, GB

Christopher Case is the Chief Technology Officer at Oxford PV, a spin-out of Oxford University (UK) that is commercialising perovskites for tandem solar cell applications. Most recently, he was the Chief Technology Officer for Linde Electronics, a gas and equipment supplier and the former Chief Scientific Officer of The BOC Group (UK). A long time chair of the International Technology Roadmap for Semiconductors, he spent 10 years at AT&T Bell Labs in Murray Hill, NJ (US). He was an assistant professor of engineering at Brown University and director of the Thin Film Institute. He was a Fulbright-Hays scholar at the Université de Bordeaux and holds a Ph.D. degree in materials science from Brown University where he studied thin film chalcopyrite photovoltaic materials.

Christopher Case a
a, Oxford PV, Yarnton, Kidlington OX5 1PF, Reino Unido, Yarnton, GB

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13:15 - 14:30
Lunch Break
Session A2
Chair: Naomi Ginsberg
14:30 - 15:00
Ardo, Shane
University of California Irvine
Leveraging Iodide Oxidation Electrocatalysts to Overcome Efficiency Limitations in Dye-Sensitized Solar Cells
Shane Ardo
University of California Irvine, US
Joseph Cardon a, Kevin Tkaczibson b, Hsiang-Yun Chen a, Shane Ardo a, b
a, Department of Chemistry, University of California, Irvine, CA 92617 USA
b, Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92617 USA

Thin films of inexpensive metal-oxide semiconductors containing surface-bound molecular dyes could serve as low-cost and robust alternatives to silicon for indoor photovoltaic applications. However, the 1 Sun power-conversion efficiencies of dye-sensitized solar cells are only half as large as those of silicon. To increase efficiency, my research group is incorporating electrocatalysts to drive multiple-electron-transfer oxidation of redox shuttles at the dye-sensitized photoanode. This design scheme allows for incorporation of dyes that are weaker oxidants when oxidized, therefore extending dye absorption into the near-infrared spectral region and increasing projected solar-cell efficiencies to beyond 20%.

Effective implementation of this innovative design requires three major developments: (1) near-infrared-absorbing dyes, (2) efficient electrocatalysis of two-electron-transfer iodide oxidation, and (3) generation of the active state of electrocatalysts via single-electron-transfer events with dyes. Toward (1), we have designed and synthesized four Os(II)–polypyridyl dyes that absorb light out to ~1 µm. Toward (2), we have identified two molecular motifs that drive the two-electron-transfer oxidation of iodide at low overpotential, albeit with low electrocatalytic performance. Toward (3), using nanosecond transient absorption spectroscopy we have showed that a dye-sensitized mesoporous thin film of anatase TiO2 nanocrystallites and functionalized with molecular charge acceptors can accumulate multiple oxidizing equivalents by single-electron-transfer events with oxidized dyes and through requisite self-exchange electron-transfer between surface-anchored dye molecules. This is the first report that has unequivocally shown such behavior under conditions of low-fluence (solar) excitation. Monte Carlo simulations support the observed behavior and the results are consistent with a mechanism where ~100 self-exchange electron-transfer events occur between dye molecules prior to oxidation of the molecular charge acceptors. Slow charge recombination between electrons in TiO2 and the oxidized molecules anchored to the surface of TiO2 enabled this demonstration. In follow-on work we have developed models for Monte Carlo simulations of these processes in mesoporous thin films. Simulating both pulsed-light and continuous-wave illumination conditions, we have identified several scenarios where rate-limiting mechanistic behavior changes from first-order to second-order in oxidized dye and combinations thereof. Together, these data may help explain the non-ideal and complex recombination kinetics observed for molecules bound to TiO2 nanocrystallites that cannot be wholly explained by trap-state energy distributions in TiO2.

Collectively, the results described herein validate the new proposed mechanistic processes and suggest that there may in fact be clear pathways to enable dye-sensitized devices with > 20% efficiency.

15:00 - 15:15
Sangiorgi, Nicola
ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council of Italy, Via Granarolo 64, 48018 Faenza, RA, Italy.
Molecular Imprinted Polypyrrole Counter Electrode for Quasi-Solid DSSCs
Nicola Sangiorgi
ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council of Italy, Via Granarolo 64, 48018 Faenza, RA, Italy.
Nicola Sangiorgi a, Alex Sangiorgi a, Alessandra Sanson a
a, ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council of Italy, Via Granarolo 64, 48018 Faenza, RA, Italy.

The chemical complexity of traditional Dye Sensitized Solar Cells (DSSCs) electrolyte requires the development of high selectivity and catalytic materials as counter electrode for the triiodide target molecule [1]. Molecular Imprinting Polymers (MIP) are a specific class of materials able to assure a high selectivity versus a dedicated target molecule in complex matrix and are therefore used in high performance sensors and chromatographic applications [2,3]. Moreover, these materials can be easily synthetized by low cost and environmentally friendly processes. In this work, an application of MIPs materials as counter-electrode in “Platinum free” Dye-Sensitized Solar Cells (DSSCs) was introduced to enhance the selectivity towards triiodide molecule (the target) contained in the electrolyte. The latter is commonly a complex matrix containing other than the target molecule other compounds used as additives and stabilizers that can compete with the triiodide reduction. Polypyrrole was used as “Non-Imprinted” (NIP) and “Imprinted” polymer (MIP) and was prepared by an electrochemical method. In order to demonstrate the positive effect of MIP on the catalytic activity at the counter electrode, two different template molecules were used: Glycine and L-Alanine (the first one with similar surface to the triiodide one and the second one with higher surface). The influence of different concentrations of Glycine template (25-50 and 100 mM) on the electrochemical and catalytic properties of PPy on triiodide reduction was studied both on 3-electrodes cell and symmetrical cells. Quasi-solid DSSCs (with polymeric electrolyte) with MIP-PPy based on the lowest Glycine concentration (25mM) produce the best results increasing the photovoltaic efficiency of the devices (close to 20%) as a consequence of the lowering charge transfer resistance (reduced to 50%). These results are mainly due to the MIP high selectivity on triiodide instead of the NIP system. This work open the possibility for the first time to apply MIP materials into energy systems based on DSSCs improving their properties.

15:15 - 15:30
Holliman, Peter
Swansea University
Surface Engineering Dye-sensitized Solar Cells
Peter Holliman
Swansea University, GB
Peter Holliman a, Christopher Kersahw a, Diana Meza-Rojas a, Rosie Anthony a, Eurig Jones a, Leo Furnell a, Arthur Connell a, James McGettrick a, Dawn Geatches b, Sebastian Metz b, Kakali Sen b
a, College of Engineering, Swansea University, Bay Campus, Swansea, SA1 8EN, UK
b, Scientific Computing Department, STFC Daresbury Laboratory, Daresbury, Warrington, UK

There are two key interfaces in dye-sensitized solar cell (DSC) devices; the dye-TiO2 and the dye-electrolyte interface. Most DSC devices are manufactured by submersion dyeing of TiO2 followed by either wetting with liquid electrolyte or by spin coating of a hole transport material (HTM). In practice, this means that dyes and HTM molecules will arrange themselves in whatever is the lowest energy orientation even if this is less favourable to device operation.

The paper will describe our current approaches to surface engineer these interfaces by combining theoretical and experimental approaches1 to designing dye and HTM molecules and processing conditions which enable interfacial self-assembly. This is particularly important when multiple species are involved (e.g. during co-sensitization)2,3 and/or for solid-state DSC devices where the use of solid electrolytes effectively “freezes” interfacial configurations.

In particular, this paper will describe theory versus s experiment for:

- optimising co-sensitization versus the AM1.5 spectrum using optical density, dye loading and TiO2 thickness

- understanding the orientation of dyes and HTMs on TiO2 versus loading using DFT and angle-resolved X-ray photoelectron spectroscopy

- self-assembly approaches at the dye-TiO2 and dye-HTM interface.

The paper will conclude with a consideration of the maximum theoretical device efficiency possible using these approaches.

15:30 - 15:45
Pinto, Ana Lucia
NOVA School of Science and Technology
On the Role of the Anchoring Unit in the Efficiency of Pyranoanthocyanin-based Dye-Sensitized Solar Cells
Ana Lucia Pinto
NOVA School of Science and Technology, PT
Ana Lucia Pinto a, Luis Cruz b, Vânia Gomes b, Hugo Cruz a, Giuseppe Calogero c, Victor de Freitas b, A. Jorge Parola a, Fernando Pina a, J. Carlos Lima a
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, CNR, Instituto per i Processi Chimico-Fisici, Sede di Messina, Salita Sperone, C. da Papardo, I-98158 Faro Superiore Messina, Italy.

Dye-Sensitized Solar Cells (DSSCs) are photovoltaic devices based on the sensitization of wide band-gap semiconductor electrodes with dyes absorbing visible light. Following the work of Grätzel, several types of pigments such as the original ruthenium(II) complex,[1] and organic dyes,[2] have been used as light absorbers. The first reported DSSC using natural anthocyanin dyes extracted from blackberries displayed a conversion yield of 0.56%.[3] Anthocyanins are the main polyphenolic dyes found in young red wines, which are transformed into more stable structures such as pyranoanthocyanins, during wine ageing and maturation. While anthocyanins practically lose their red color between pH 1 and 5, as a result of the formation of colorless hemiketals, their relative compounds pyranoanthocyanins are more resistant to hydration and keep colour in the visible over a wide pH range.[4] Thus, they constitute a photosensitizer family with great potential for bio-inspired DSSCs. Still, the best known efficiency reported so far using this family of compounds is 0.006% for cyanidin-3-O-glucoside-pyruvic acid adduct.[5]

When considering naturally occurring dyes, betalains which contain carboxylates as anchoring groups show higher efficiencies compared to anthocyanins.[6] This led to the idea that carboxylic linkage was essential in order to have strong electronic coupling and rapid forward and reverse electron transfer reactions between the dye and the DSSC.[6] In this work, a series of bio-inspired pyranoanthocyanin derivatives were designed, synthesized and applied for the first time as dye sensitizers in DSSCs. Furthermore, both anchoring groups (carboxyl and catechol) were compared within closely related molecules with the same pyranoflavylium core. A relation was established between dye structure and cell efficiency. Specifically, the presence of the catechol unit was shown to increase electron injection to the TiO2 semiconductor. An overall efficiency of 1.15% was obtained for the best performing compound, with no further optimization.

15:45 - 16:00
Bonomo, Matteo
University of Turin, Department of Chemistry and NIS Interdepartmental Center
Effect of the Sintering Procedure on the Photoelectrochemical Performances of Nanostructured Mixed Oxides as Photocathodes of p and Tandem Dye-Sensitized Solar Cells with Superior Conversion Properties
Matteo Bonomo
University of Turin, Department of Chemistry and NIS Interdepartmental Center, IT
Matteo Bonomo a, b, Emmanuel Ekoi c, Claudia Barolo a, Denis Dowling c, Danilo Dini b, Aldo Di Carlo d
a, University of Turin, Department of Chemistry and NIS Interdepartmental Center, Via Pietro Giuria, 7, Torino, 10125, IT
b, Department of Chemistry Chemistry, University of Rome La Sapienza, Piazzale Aldo Moro 5, 00185, Rome
c, School of Mechanical and Materials Engineering, University College Dublin (UCD), Belfield, Dublin 4, Dublin, IE
d, CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, Via del Politecnico, 1, Roma, IT


P-type dye sensitized solar cells (p-DSCs) suffer low performances compared to the n-type counterpart[1]. One of the main causes of this is the fast recombination reaction occurring between the photoinjected holes in the valence band of the p-type semiconductor (usually NiO) and the reduced form of the redox shuttle (typically I-). As a matter of fact, recombination phenomena at the NiO/electrolyte interface heavily limit both photovoltage and photocurrent. Different approaches have been adopted to minimize such an unwanted process: these range  from the pretreatment of the electrode surface with NaOH[2] to the employment of passivating organic molecules (e.g. CDCA) in the sensitizing solution and/or in the electrolyte solution.[3]


The present contribution describes the implementation of metal oxide (MOx in which M is Al, Zr, Y or Ce) nanoparticles (NPs) as anti-recombination agent in NiO-based photocathodes for p-DSCs. MOx NPs (diameter, Ø = 20 nm) and NiO nanoparticles (Ø < 50 nm) were dispersed together in a methanol solution and spray-deposited onto FTO. Different MOx/NiO molar ratio (ranging from 1 to 20%) were considered. The as deposited films were annealed at 450 °C in a conventional oven or by Microwave-assisted Rapid Discharge Sintering (RDS). The latter method was proved to be more effective by assuring the formation of a more porous, able to load more sensitizer (i.e. P1) molecules, and electroactive film. Scanning Electron Microscopy (SEM) was used to check the morphology of the electrodes and the effective dispersion of MOx NPs. It was proved that the nature and the electrochemical and optical properties of MOx deeply influence the photoelectrochemical behavior of photocathodes. Indeed, the optimal MOx/NiO ratio is strongly dependent on the nature of the metal oxide but all tend to form aggregates and macrostructures if their relative concentration exceeds 10%.


Among the investigated MOx NPs, Zirconium Oxide (ZrO2) was found to be the most performing additive: an 80% enhancement of the photoconversion compared to unmodified photocathode was obtained following on from the minimization of recombination reactions at the electrode/electrolyte interface as proved by Electrochemical Impedance Spectroscopy. Very interestingly, the addition of Y2O3 (ratio 0.02%) has a positive effect on the open circuit voltage (i.e. > 0.145 mV) of the device whereas Al2O3 (ratio = 0.10%) allows to boost the photocurrent powered (i.e. > 3.5 mA*cm-2) by the cell.


The most performing cell (i.e. ZrO2/NiO-based electrode sintering by RDS and sensitized with P1) produced a JSC up to 3.6 mA*cm-2, a VOC of 129 mV leading to an overall efficiency of 0.164%. Furthermore, this photocathode was coupled with a VG10-sensitized TiO2-based photoanode to produce a tandem DSC with an overall efficiency close to 2% (JSC = 4.2 mA*cm-2, a VOC = 678 mV and FF = 0.66%).


16:00 - 16:30
Coffee Break
16:30 - 16:45
Barker, Alex
Fondazione Istituto Italiano di Tecnologia
Facile Exciton Diffusion in Fused Ring Electron Acceptor Films
Alex Barker
Fondazione Istituto Italiano di Tecnologia, IT

Alex Barker is a researcher in the groups of Annamaria Petrozza and Guglielmo Lanzani at the Center for Nanoscience and Technology in Milan, Italy. He received his PhD from Victoria University of Wellington (New Zealand). His core research interests focus on ultrafast spectroscopy of hybrid organic perovskites and organic photovoltaics.

Sreelakshmi Chandrabose a, b, Kai Chen a, b, Alex J. Barker c, Joshua J. Sutton a, d, Shyamal Prasad a, b, Jingshuai Zhu e, Keith C. Gordon a, d, Zenqi Xie f, Xiaowei Zhan e, Justin M. Hodgkiss a, b
a, The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
b, School of Chemical and Physical Sciences, Victoria University of Wellington, New Zealand
c, Center for NanoScience and Technology, Italian Institute of Technology, Via Pascoli 70/3, 20133 Milano, Italy
d, Department of Chemistry, University of Otago, New Zealand
e, Department of Material Science and Engineering, College of Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Peking University, Beijing 100871, China
f, Institute of Polymer Optoelectronic Materials and Devices, Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Modest exciton diffusion lengths dictate the need for nanostructured bulk heterojunctions in organic photovoltaic (OPV) cells, however, this morphology compromises charge collection. Here, we reveal facile exciton diffusion in films of a fused-ring electron acceptor that, when blended with a donor, already outperforms fullerene-based OPV cells.

Temperature-dependent ultrafast exciton annihilation measurements are used to resolve a quasi-activationless exciton diffusion coefficient of at least 2 ×10-2 cm2 / s – substantially exceeding typical organic semiconductors, and consistent with the 20-50 nm domain sizes in optimized blends. Enhanced 3-dimensional diffusion is shown to arise from molecular and packing factors; the rigid planar molecular structure is associated with low reorganization energy, good transition dipole moment alignment, and low disorder – all enhancing long-range resonant energy transfer.

Relieving exciton diffusion constraints has important implications for OPVs; large, ordered, and pure domains enhance charge separation and transport, and suppress recombination, thereby boosting fill factors. Long exciton diffusion lengths also adds tolerance to morphology variation, and further enhancements may even obviate the need for the bulk heterojunction morphology.

16:45 - 17:00
Bellchambers, Philip
University of Warwick
High-Performance Cu Mesh Transparent Conductive Electrodes for Flexible Organic Photovoltaics
Philip Bellchambers
University of Warwick, GB
Philip Bellchambers a, Silvia Varagnolo a, Ross Hatton a
a, Department of Chemistry, University of Warwick, CV4 7AL, Coventry, United Kingdom

There is a clear need for a new transparent electrode compatible with flexible organic photovoltaics (OPVs) and made from low-cost raw materials. This talk will present a high-performance copper (Cu) electrode based on a Cu grid fabricated by soft lithography and demonstrate its utility in PV devices with ~10% efficiency. Even before the addition of an anti-reflecting charge transport layer the electrode has an average far field transparency of ≥ 85% which is achieved for a sheet resistance < 10 Ω sq-1. The novelty of the fabrication process is twofold: (i) an extremely rapid and clean metal etch process using a low toxicity etchant (ii) an ultrathin mask which can remain in place after etching without consequence, which together speed up and simplify electrode fabrication and integration into OPV devices. At ~1% the material cost of comparable Ag-mesh electrodes, we show these electrodes can compete with indium tin oxide (ITO) as the transparent electrode in high-performance OPVs with further advantages through their inherent flexibility.

17:00 - 17:15
Pascual San José, Enrique
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC
High Throughput Screening of Highly Efficient Non-fullerene Acceptor based Organic Solar Cells Assisted by a Multi-Dataset Scientific Robot
Enrique Pascual San José
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC, ES
Enrique Pascual-San-José a, Xabier Rodríguez-Martínez a, Fei Zhuping b, Martin Heeney b, Roger Guimerà-Manrique c, Mariano Campoy-Quiles a
a, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC, Campus UAB, Bellaterra, ES
b, Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London, GB
c, Departament d’Enginyeria Química, Universitat Rovira i Virgili, Tarragona, ES

Organic photovoltaics (OPVs) have experienced an impressive performance enhancement over the past few years, recently going beyond the 15% milestone [1]. Current record devices rely on the combination of low-bandgap polymers blended with small acceptor molecules (also called non-fullerene acceptors, NFA). The vast majority of studies in the OPV field follows a traditional Edisonian optimization approach for the optimization of cells based on these systems. This, however, entails manufacturing tens to hundreds of devices in order to optimize the solar cell parameters such as: donor:acceptor ratio, thickness of the active layer, solvent system and thermal annealing. Thus, requiring a large amount of semiconductor materials, time and human resources.

We present a novel gradient methodology [2] based on controlled variation of the parameters of interest allowing to save both resources and research time. This methodology consists in three basic steps. First, donor (low bandgap polymer): acceptor (NFA) composition gradient is produced and measured using RamBIC. This tool extracts the composition and thickness from Raman hyperspectral images, and simultaneously and co-locally determines the photocurrent using the same laser to produce LBIC (laser-beam induced current) images. These images contain typically 10.000 data points. The comparison between images identifies the optimum values for thickness and composition. Then, the RamBIC predictions are double checked (and extended to the rest of the cell parameters) by producing doctor-bladed OPV devices with optimum thickness and composition combinations. Finally, the large dataset are used to train a multi-dataset scientific robot that uses artificial intelligence to try to identify an empirical equation that models all RamBIC data (Figure 1) for different OPV system.

17:15 - 17:30
Walsh, Kieran
School of Physics, University of Exeter
FeCl3 intercalted graphene electrodes for photovoltaic energy harvesting
Kieran Walsh
School of Physics, University of Exeter
Kieran Walsh a, Conor Murphy a, Adolfo De Sanctis a, Christos Melios b, Saverio Russo a, Monica Craciun a
a, School of Physics, University of Exeter, Stocker Road, Exeter, Devon EX4 4QL
b, National Physical Laboratory, Hampton Road, Teddington, TW11 0LW

Over the past decades the efficiency of Organic Photovoltaics (OPVs) and Perovskite Photovoltaic devices has improved at an alarming rate, now both exceeding the efficiency of commercial silicon based photovoltaic devices [1]. However, due to a lack in flexible transparent electrodes, most OPV and perovskite technologies are limited to fabrication on Indium Tin Oxide (ITO) electrodes.  While these are the leading transparent conducting electrode material in industry, ITO lacks the flexibility to truly utilize the advantageous properties of OPVs and perovskite photovoltaic devices.  In addition, ITO has been shown to greatly increase the energy cost of production of OPV devices [2], thereby increasing the energy payback required from them.  In recent years graphene has been heralded as a wonder material with a plethora of uses in optoelectronic devices, photovoltaics and many other areas of scientific interest.  However, the limited quality of graphene produced by Chemical Vapour Deposition (CVD) means that graphene grown by this method still has a relatively high sheet resistance (≈ 1000 Ω/sq).  Graphene also has a relatively low work function (≈ 4.4 eV), necessitating the use of electron/hole transport layers in OPV devices that incorporate graphene electrodes.  These factors would make graphene unsuitable for use in OPV and perovskite photovoltaic devices, however the chemical doping of graphene has been shown to have profound effects on the electrical properties of the material, while leaving its optical properties unchanged.  Here we report the characterization of large area Few Layer Graphene (FLG) electrodes grown by CVD on Ni substrates, functionalized by intercalation with ferric chloride (FeCl3), suitable for flexible photovoltaic devices.  This non-volatile doping method proves to be effective at tuning both the sheet resistance and work function of graphene [3], while being extremely stable to changes in both temperature and humidity [4].  Strong p-doping through charge transfer from the intercalant is characterized by mapping the concomitant shift in G-peak by Raman spectroscopy.  Scanning Kelvin Probe Force Microscopy (SKPFM) was used to characterize variations in the surface potential of the intercalated graphene caused by non-uniform intercalation between the graphene sheets.  This allows the work function of the intercalated graphene to be mapped, increasing up to 4.97 eV due to surface doping from the intercalation process.  Electrical measurements of macroscopic sized hall bar devices shows intercalation to reduce the sheet resistance by an over order of magnitude to ≈ 50 Ω/sq, due to a massive increase in charge carrier concentration to ≈ 1x1015 cm-2.  This low sheet resistance, combined with the transparency and inherent flexibility of graphene makes FeCl3 intercalated graphene a promising material for flexible photovoltaic and optoelectronic technologies.  OPV devices composed of PTB7-th and PC70BM donor/acceptor molecules, fabricated on flexible intercalated graphene electrodes are compared to those on ITO/glass substrates.  This functionalized graphene material has the potential to realize a new generation of fully flexible solar cells, expanding the applicable environments for photovoltaic technologies.

Session B2
Chair: Eva Barea
14:30 - 14:45
Galisteo-López, Juan
Instituto de Ciencia de Materiales de Sevilla (ICMS-CSIC)
Mechanism of Photoluminescence Intermittency in Organic−Inorganic Perovskite Nanoparticles
Juan Galisteo-López
Instituto de Ciencia de Materiales de Sevilla (ICMS-CSIC)
Juan F. Galisteo-López a, Mauricio E. Calvo a, Cristina T. Rojas a, Hernán Míguez a
a, Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Cient&#8055;ficas, c/ Américo Vespucio 49, Sevilla, 41092

Reducing the dimensions of lead halide perovskites down to the nanoparticle (NP) level can further expand the acknowledged potential of this material for optoelectronic applications. One example is their use in light emitting devices as a promising route to improve their performance. [1] A limitation of these NP is the presence of photoluminescence (PL) intermittency which lowers its quantum efficiency and could compromise its applicability. Such PL blinking has been observed in lead halide perovskites of different nature and morphology and its precise origin has not yet been clarified.

In this work we have studied the PL temporal evolution of crystalline CH3NH3PbBr3 NPs having an average size of 40nm, well above the Bohr’s exciton radius for this material and thus far from the quantum confinement regime. The NPs present a PL which oscillates between different intensity levels when illuminated over a period of several minutes under continuous wave illumination. Contrary to inorganic quantum dots where such intermittency takes place as a sucesion of on/off states, multiple PL levels are observed for the perovsktie NPs.

In order to understand such PL intermittency we have exposed the NPs to different atmospheres. We find that the PL intermittency remains upon changes in the surrounding atmosphere though the higher and lower PL levels dominate when the NPs are exposed to O2 and N2 respectively. Based on these findings and previous ones dealing with the emission of the bulk material [2] we propose a mechanism for the PL intermittency in which an interplay between photoinduced trap creation/annihilation takes place as a consequence of the interaction between the photoexcited NP and the atmosphere. [3] 

14:45 - 15:00
Spalla, Manon
LEPMI/Savoie-Mont-Blanc University/CEA
Stability of mixed cation perovskite solar cells: understanding of involved mechanisms
Manon Spalla
LEPMI/Savoie-Mont-Blanc University/CEA, FR
Manon Spalla a, b, Lara Perrin a, Emilie Planes a, Muriel Matheron b, Solenn Berson b, Lionel Flandin a
a, LEPMI / Université Savoie Mont Blanc
b, University Grenoble Alpes, CEA-LITEN

In the field of photovoltaics, the recent concept of perovskite solar cells has attracted great interest due to their high efficiency combined with a potential low cost and good versatility. One of the main remaining challenges now concerns their intrinsic stability. There is a vital need for a better understanding of the degradation mechanisms and thereby the possible mitigation strategies. The presented work focuses on degradation mechanisms taking place in the double cation perovskite solar cells. The studied perovskite is the following: FA0,95Cs0,05Pb(I0,83Br0,17)3. This material is well known for its high and stabilized performances [1,2]. In order to validate the enhanced stability of mixed cation perovskite compared to the common MAPbI3 monocation one, ageing tests were conducted using an innovative device architecture compatible with both low temperature processes and semi-transparent devices for tandem cells development.

The conducted experiments are resumed on figure 1. Three conditions were tested to study the precise impact of each possible constraint: temperature, oxygen and humidity. Thanks to an optimized characterization set composed of X-ray diffraction, UV-visible absorption, photoluminescence, FTIR spectroscopy, power conversion and external quantum efficiencies, interlinked with special resolved mapping techniques such as photoluminescence and light beam induced current imagings and RGB analysis, the global degradation behaviour of mixed cation perovskite was draft. Ageing of partial stacks was also conducted in order to confirm obtained results. Interesting results such as the good humidity tolerance of the material were obtained. Under drastic conditions (85°C/Air/40%RH), even if an important loss of photovoltaic properties (62%) occurred during the first 150h, the performances were then exceptionally stabilized for more than 500h with a 5.2%  power conversion efficiency.

15:00 - 15:15
Horvath, Endre
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
Lead Halide Perovskite Nanowires: Quest for Liquid Phase Wafer-scale Epitaxial Growth
Endre Horvath
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH
Endre Horvath a, d, Massimo Spina a, Balint Nafradi a, Eric Bonvin a, Marton Kollar a, Andrzej Sienkiewicz a, Konstantins Matulnikovs a, Anastasiia Glushkova a, Alla Arakcheeva a, Zsolt Szekrenyes b, Hajnalka Tohati b, Katalin Kamaras b, Richard Gaal c, Pavao Andricevic a, Rita Smajda d, Raphael Pugin d, Laszlo Forro a
a, Institute of Physics (IPHYS), SB, EPFL Ecole Polytechnique Federale de Lausanne, Switzerland, Station 3, Lausana, CH
b, Wigner Research Centre for Physics
c, Institute of Physics (IPHYS), SB, EPFL Ecole Polytechnique Federale de Lausanne, Switzerland, Station 3, Lausana, CH
d, CSEM SA, Tramstrasse 99, Muttenz, 4132, CH

Understanding the crystallization is one of the most pressing task in order to make the halide perovskite based technologies reproducible and reliable. In this work a common mechanism underlying of hybrid perovskite nanowire formation will be discussed in detail [1]. The central role of the solvatomorph phase as the intermediate phase in crystallization will be highlighted. Guided growth of perovskite nanowires by ‘solvatomorph-graphoepitaxy’ will be presented [2]. This method turned out to be a fairly simple approach to overcome the spatially random surface nucleation. The process allows the synthesis of extremely long (centimeters) and thin (a few nanometers) nanowires with a morphology defined by the shape of nanostructured surface features, for example open fluidic channels. This method might allow the integration of perovskite nanowires into advanced CMOS technologies. Along this road, our latest findings on ink-jet printed perovskite nanowire films and the performances of printed sensitive photodetector will be discussed.

Solvatomorph-graphoepitaxy method could open up an entirely new spectrum of architectural designs of organometal-halide-perovskite-based heterojunctions -and tandem solar cells, LEDs, photodetectors and new type of magneto-optical data storage devices [5].


15:15 - 15:30
Akkerman, Quinten
Istituto Italiano di Tecnologia (IIT), Genova, Italy
Beyond the crystal lattice of lead halide perovskites: The curious cases of Cs4PbX6, Cs(Pb:Mn)I3, Cs2PbI2Cl2 and CsPb(Cl:Br:I)3 nanocrystals
Quinten Akkerman
Istituto Italiano di Tecnologia (IIT), Genova, Italy, IT
Quinten A. Akkerman a, Liberato Manna a
a, Istituto Italiano di Tecnologia (IIT), Genova, Italy, Via Morego, 30, Genova, IT

Nanocrystals (NCs) of cesium lead halide perovskites (LHP) have recently become an extensive research topic, owing due to their interesting optical properties.1-2 The LHP CsPbX3 phase, with X = Cl-, Br- or I-, is characterized by corner sharing PbX64- octahedra, with the Cs+ cations filling the voids created by four neighboring PbX64- octahedra. Here, we will present recent works focusing on the cesium LHP structure, and how altering the lead-halide framework strongly alters the structural and optical properties of these cesium LHPs.

In this presentation, we will first briefly focuses on Cs4PbX6 NCs, and how these type of NCs exhibit optical absorption with sharp, high energy peak due to transitions between states localized in individual PbX64– octahedra.3 Because of the large band gap of Cs4PbX6 (>3.2 eV), no excitonic emission in the visible range was observed.4 The Cs4PbBr6 nanocrystals can be converted into green fluorescent CsPbBr3 nanocrystals by their reaction with an excess of PbBr2 with preservation of size and size distributions. We will also briefly the case alloyed CsPbxMn1–xI3 nanocrystals.5 These NCs have essentially the same optical features and crystal structure as the parent α-CsPbI3 system, but they are stable in films and in solution for periods over a month. The stabilization stems from a small decrease in the lattice parameters slightly increasing the Goldsmith tolerance factor, combined with an increase in the cohesive energy. Finally, hybrid density functional calculations confirm that the Mn2+ levels fall within the conduction band, thus not strongly altering the optical properties.

Finally, we will focuses on two novel types of LHP related NCs.6. The vast majority of LHP (both as thin films and NCs) are currently based on either a single halide compositions (CsPbCl3, CsPbBr3, CsPbI3) or an alloyed mixture of bromide with either Cl- or I- (i.e. CsPb(Br:Cl)3 or CsPb(Br:I)3). Here. we present the synthesis, as well as a detailed optical and structural study of two halide alloying cases that have not previously been reported for LHP NCs: Cs2PbI2Cl2 NCs and triple halide CsPb(Cl:Br:I)3 NCs.REF In the case of Cs2PbI2Cl2, we observe for the first time fully inorganic LHP NCs with a Ruddlesden-Popper phase (RPP) crystal structure. Unlike the well-explored organic-inorganic RPP, here, the RPP formation is triggered by the size difference between the halide ions (Cl and I). In the case of the triple halide CsPb(Cl:Br:I)3 composition, the NCs comprise a CsPbBr2Cl perovskite crystal lattice with only a small amount of incorporated iodide, which segregates at RPP planes’ interfaces within the CsPb(Cl:Br:I)3 NCs. Supported by density functional theory calculations and post-synthetic surface treatments to enhance PLQY, we show that the combination of iodide segregation and defective RPP interfaces are most likely linked to the strong PL quenching observed in these nanostructures.

15:30 - 16:00
Nag, Angshuman
Indian Institute of Science Education and Research (IISER) Pune
Mn- and Yb- Doping in Metal Halide Perovskite Nanocrystals
Angshuman Nag
Indian Institute of Science Education and Research (IISER) Pune
Angshuman Nag a
a, Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune 411008, India

Colloidal nanocrystals of lead halide perovskites exhibit interesting structural, optical and optoelectronic properties, some of which are very different compared to their bulk counterparts. In last four years, we have been working on cesium lead halide perovskite nanocrystals and Pb-free metal halides such as thallium halide, cesium antimony halide, and cesium bismuth halide nanocrystals. While I will mention about a few aspects of material design and photophysical properties Pb-halide and Pb-free halide nanocrystals, the major emphasis of the talk will be on our recent results on Mn and Yb doped into B-site (Pb-site) of metal halide perovskite nanocrystals.

We have developed a postsynthesis doping method where Mn and Yb are doped into pre-formed colloidal CsPbX3 (X = Cl, Br, I) nanocrystals. The dopants Mn and Yb emits in the red and near-infrared regions, with huge (~1 eV) Stoke’s shift compared to the absorption (of host) spectrum. We have got similar downconversion luminescence by doping Mn and Yb into Pb-free Cs2AgInCl6 double perovskites as well. Interestingly, the postsynthesis Mn doping provides stability to black perovskite phase of CsPbI3 nanocrystals in the ambient conditions for about a month. I will discuss about the role of surface energy and lattice energy in stabilizing the balck phase by Mn-doping. Overall, doping the B-site of metal halide perovskites is an interesting strategy to tailor optical properties and stabilities of perovskites.   

16:00 - 16:30
Coffee Break
16:30 - 16:45
Toin University of Yokohama
Performance Deterioration and Stability issues with Organic-inorganic hybrid and All-inorganic Perovskite Solar Cells
Toin University of Yokohama, JP
Ajay Jena a, Tsutomu Miyasaka a
a, Graduate School of Engineering, Toin University of Yokohama, 1614, Kurogane-cho, Aoba, Yokohama, Kanagawa, Japan 225-8503

Despite an expeditious rise in its power coversion efficiency organolead halide perovskite solar cells (PSCs) still stand way behind commercialization because of two major challenges; poor stability and high toxicity of Pb. In a recent study on thermal stability of regular MAPbI3 solar cells, we found that spiro-OMeTAD (used as hole transporting material) plays a notorious role in performance deterioration of the cells at elevated temperatures. It seems that, not the degradation of perovskite (MAPbI3) but some physical/chemical alteration at the perovskite/spiro-OMeTAD interface is a more serious cause of performance degradation in the MAPbI3 cells. Recovery of performance after recycling the degraded device by replacing with a fresh HTM layer depends on composition of perovskite, indicating loss of organic cation being involved in the process. As organic part of hybrid perovskites is believed to be responsible for poor thermal stability of these materials, all-inorganic CsPbX3 perovskites are gaining much interest these days. However, the challenge in CsPbI3 perovskties is the stabilization of its photoactive black phase under ambient conditions (at room temperature) because the balck phase is formed only at temperature above 300 oC. We have found that Eu (Eu2+ or Eu3+) inclusion into CsPbI3 precursor solution can form the black phase at ambient conditions (85 oC). Remarkable reduction of crystal/grain size possibly results in formation of the high symmetry cubic phase (α-CsPbI3). The devices made from such Eu-stabilized photoactive CsPbI3 (CsPbI3:xEu) perovskites demonstrate a power conversion efficiency of around 7% at best conditions. Nevertheless, there are number of challenges in improving the long term stability of the photoactive phase of these all-inorganic perovksites. These issues and possible ways to address them will be discussed.

16:45 - 17:00
Polyakov, Alexander
National University of Science and Technology "MISiS"
Admittance spectroscopy and DLTS measurements on multication mesoscopic perovskite solar cells
Alexander Polyakov
National University of Science and Technology "MISiS", RU
Alexander Polyakov a, Nickolay Smirnov a, Ivan Shcemerov Shchemerov a, Danila Saranin b, Anna Pozniak c, Ali Sehpar Shikoh a, b, Sergey Didenko a, Denis Kuznetsov c, Antonio Agresti d, Sara Pescetelli d, Fabio Matteocci d, Aldo Di Carlo b, d
a, Department of Semiconductor Electronics and Device Physics, National University of Science and Technology MISiS, Leninsky Avenue, 4, Moskva, RU
b, LASE–Laboratory for Advanced Solar Energy, National University of Science and Technology MISiS, Leninsky Avenue, 6, Moskva, RU
c, Department of Functional Nanosystems and Hightemperature Meterials, NUST MISiS, Leninsky Avenue, Moskva, RU
d, CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, Via del Politecnico, 1, Roma, IT

Several questions still remain open regarding the electronic structure of perovskite-based solar cells (PSCs): i) the nature, levels position and concentration of centers pinning the Fermi level in halide perovskite (PS) films in dark conditions, ii) the possible contribution to the admittance of ionic conductivity in PS layers and the role of ions movement in PSCs' degradation, iii) the type of deep traps present in various parts of PS layer and the way these deep spectra are affected by varying the PS film composition and iv) the possible role of various deep level defects in photoelectrical performance. To shed light on these issues, we studied trap levels of multication lead halide perovskites in mesoscopic PSCs by means of capacitance-voltage (C-V), capacitance-frequency (C-f), admittance spectra (AS) and deep levels transient spectroscopy (DLTS) analysis.  The investigation was performed on several PSCs with and without the use of 2D materials to tune cell’s performances. For all PSCs, with and without 2D materials, the dark conductivity in the PS layer is determined by the presence of relatively deep centers with levels near 0.2 eV below the conduction band edge (Ec) showing a strong freeze-out in AS spectra at temperatures below 200K. These centers invariably demonstrate strong concentration build-up near the interface with the electron transport layer while the bulk of the PS films is almost fully depleted for an applied bias of 0 V. The low frequency capacitance of PSCs showed a strong increase with frequency indicating considerable contribution of the ionic conductivity. Although with similar thickness, all PS layers showed a considerable spread in the apparent thickness as determined from C-V profiling under the assumption that the PS permittivity is constant. This suggests that, even at high frequencies where the capacitance shows a plateau, the actual permittivity could be different, possibly due to different impact of ionic conductivity or that the thickness of the accumulation layer near the interface varies strongly for different OSCs. DLTS spectra are always dominated by 1-2 hole traps with levels near ~Ev+0.6 eV or ~Ev+0.8 eV and 1-2 electron traps with levels near ~Ec-0.7 eV and Ec-0.9 eV [1] in reasonable agreement with theoretical results [2]. All the centers show a measurable dependence of respective DLTS peaks magnitude on the injection pulse length, which is not easily compatible with the apparent capture cross sections determined from standard DLTS analysis. This suggests that some of the traps possess a sizable barrier for capture of charge carriers.   From recent theoretical calculations [3] one would expect that only the electron and hole traps near midgap should significantly limit the lifetime of charge carriers created by light. This conclusion is partly corroborated by the results of DLTS analysis performed on the different PSCs where we observe some correlation between changes in cell efficiency and the signal from the Ec-0.9 eV electron traps. We also report on a serious changes in C-V profiles occurring after several temperature runs under applied bias during DLTS and optical DLTS (ODLTS). These changes are somewhat tentatively attributed to ion movement in PS film. In ODLTS spectra such movement results in the appearance of a strong hole-trap-like peaks with activation energies exceeding the bandgap of the PS films. We discuss possible means of quantitative assessment of the activation energies involved in ions movement and its impact on the high-frequency dielectric permittivity of PS films.

17:00 - 17:15
Noel, Nakita K.
Princeton University
Interfacial Charge-transfer Doping of Metal Halide Perovskites for High Performance Optoelectronics
Nakita K. Noel
Princeton University, US
Nakita K. Noel a
a, Princeton University, Dept. Electrical Engineering, Princeton , 8540, US

Within the past few years, metal halide perovskites have been attracting significant interest due to their successful application to optoelectronic devices. These materials have been used in lasers, photodetectors, and most commonly, in photovoltaic devices and light emitting diodes. Despite the cheap and simple fabrication methods by which these materials are deposited, high quality perovskite films can be readily fabricated, and the power conversion efficiencies of lead halide perovskite solar cells are now approaching certified values of 23%. However, perovskite-based devices are yet to achieve their full potential. One of the major hindrances to achieving this potential is an incomplete understanding of perovskite surfaces and interfaces. Deficiencies at these interfaces may be responsible for the largest losses in perovskite based optoelectronic devices; hindering charge extraction, increasing non-radiative recombination rates and hysteresis, and significantly increasing the voltage loss perovskite photovoltaics. We propose surface doping of the perovskite material as a means to combat these interface deficiencies. Herein, we will discuss doping of the perovskite material at various interfaces using well-established charge-transfer dopants. We show the doping of the perovskite material through both solid-state NMR and surface characterisation techniques, and further characterise the material through photoluminescence measurements, showing a reduction in the non-radiative recombination. Using this method of interface doping, we show photovoltaic devices with reduced hysteresis, low voltage losses, steady-state power conversion efficiencies in excess of 20%, and improved stability. Additionally, we extend this approach beyond photovoltaics and show the beneficial impacts of this type of interface engineering on perovskite-based light emitting diodes.

17:15 - 17:30
Lim, Jongchul
Oxford university
Elucidating the Long-range Charge Carrier Mobility in Metal Halide Perovskite Thin Films
Jongchul Lim
Oxford university
Jongchul Lim a, Bernard Wenger a, Henry Snaith a
a, University of Oxford, GB

Various charge carrier mobility under different carrier densities regime have been reported for lead halide perovskite polycrystalline films.[1-3] However, ambiguities in the evaluation of these properties remain, especially time-dependent change of internal carrier population due to early-time recombination should be reflected in long-range lateral charge transport through intragrains and grain boundaries.[1] Here we demonstrate a new transient photo-conductivity technique and accurately estimate the internal free carrier density using simulation of charge population rise and decay with the early-time recombination.[1-4] With this knowledge we determine carrier density invariable lateral mobilities to be in the range from 8.9 down to 0.2 cm2/Vs for Cs0.17FA0.83Pb(I0.9Br0.1)3, Cs0.05(FA0.83MA0.17)0.95Pb(I0.9Br0.1)3 and CH3NH3PbI3 polycrystalline perovskite films depending upon the preparation route and free carrier density. Our results provide the first accurate evaluation of the carrier density invariable lateral mobility in lead halide perovskite films, presenting the applicability of our technique to a broader set of materials and techniques in the research community.

Session C2
Chair: Udo Bach
14:30 - 14:45
Sultana, Nishat
University of Auckland
Unveiling the Degradation mechanism of Perovskite Solar Cells by the Laser Desorption/Ionization Mass Spectrometry
Nishat Sultana
University of Auckland, NZ
Nishat Sultana a, Nicholas J. Demarais a, Denys Shevchenko b
a, Department of Physics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
b, Solomya, Myskdalen 58, SE 75597 Uppsala, Sweden

Perovskite solar cells (PSCs) have achieved  rapid improvement in efficiencies starting from 3.8% in 2009 to over 20% in 2018 within a short period.  Due to their fast degradation, it is still a challenge to commercialize PSCs despite the promising enhancement in device efficiencies. Thus, it is necessary to probe the whole device in their operating condition to understand the degradation mechanism of each layer as well as intra-device reactions. In the present work, we have used laser desorption/ionization mass spectrometry (LDI-MS) to investigate the molecular interactions as well as the degradation products directly in complete perovskite solar cells. LDI-MS is a soft ionization process and has been used widely to analyze drugs, soft biological tissues, organometallic compounds, and thin films. By using this technique, we were able to observe chemical transformations such as corrosion of metal electrode, degradation of adjacent charge transport layers, incorporation of oxygen atoms into perovskite and formation of charge transfer complex between perovskite and hole transport layer [1].  We show that LDI-MS is a promising technique to observe intra-device reactions in PSCs. We believe our obtained results may shed light on the degradation mechanism inside PSCs which will, in turn, be helpful to increase the stability of the perovskite solar cells and make their commercialization feasible.  In life science research, LDI-MS method has already become an inevitable analytical tool. We believe this method has the potential to benefit the field of solar cell studies as well.

Keywords: Laser desorption/ionization mass spectrometry, perovskite solar cells

14:45 - 15:00
Yoo, Bowon
Imperial College London
Optical and Electronic Property Changes in Lead-free Perovskites by Metal Cation Transmutation
Bowon Yoo
Imperial College London, GB
Bowon Yoo a, Alex Aziz b, Dibyajyoti Ghosh b, Hyejin Park a, M. Saiful Islam b, Saif A. Haque a
a, Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London, GB
b, Department of Chemistry, University of Bath, Bath BA2 7AY, UK

  Lead-based perovskites, APbX3, achieved over 23 % of efficiency within only 7 years after first their usage in solar cells. Although these lead-based perovskites have rapidly achieved the high efficiency, they have two intrinsic problems to be addressed to be commercialised; toxicity and instability. To address the problems of lead at the same time, new lead-free and air-stable perovskites such as bismuth- or antimony-based perovskites are emerging. However, the efficiency of the solar cells employing these new materials is relatively low below 5% with intrinsic problems; large binding energy, high defect, and large band gap.[1-4]

 Recently, it was reported that 10 times higher photo luminescence quantum yield (PLQY) was achieved by 7% of tin substitution on lead-based perovskite.[5] The reason for this improvement is not clear yet but we expect the similar effect can be brought when bismuth and antimony are mixed in a perovskite structure because the relationship between lead and tin is like that between bismuth and antimony. In a report, the improvement in defect density and varied defect states with the ratio of bismuth in the antimony perovskite, leading to doubled solar cell performance.[6]

 In this talk, we will present some of our results from the investigation on the bismuth and antimony mixed perovskites in (MA)3(BixSb1-x)2I9 structure. In particular, we will focus on the changes in structure and electronic and opto-electronic properties as changing the ratio of two atoms in the 0D perovskites by both experimental and theoretical methods.

15:00 - 15:30
Hayase, Shuzi
The University of Electro-Communications
Relationship between Relative Lattice Strain and Efficiency for Sn-Perovskite Solar Cells
Shuzi Hayase
The University of Electro-Communications, JP

The author was graduated from Osaka University in 1978 and received Ph.D from Osaka University in 1983. He joined R&D Center in Toshiba from 1978 to 2000, during which the author was engaged in development of ULSI lithography, solar cells direct methanol fuel cells, and polysilane. He joined polysilane research in Robert West group of Wisconsin University (US) from 1988 to 1990. He was a professor of Kyushu Institute of Technology (National Institute) since 2001. From 2019, the author is a professor in The University of Electro-Communications in Japan. His research interest is printable solar cells.

Kohei Nishimura a, Daisuke Hirotani a, Gaurav Kapil b, Chi Huey Ng a, Kengo Hamada a, Kamarudin, Muhammad Akmal a, Ripolles Teresa c, Shen Qing d, Satoshi likubo a, Takashi Minemoto e, Kenji Yoshino f, Hiroshi Segawa b, Shuzi Hayase a
a, Kyushu Institute of Technology, 204 Hibikino Wakamatsu-ku, Kitakyushu - Fukuoka, 808, JP
b, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, JP
c, Universidad Rey Juan Carlos (URJC), C/Tulipán; s/n, Móstoles, 28933, ES
d, University of Electro-Communication
e, Ritsumeikan University, 1-1-1 norohigashi Kusatsu, JP
f, Miyazaki University, 1-1 Gakuen, Kibanadai-nishi, Miyazaki 889-2192, JP

Sn-perovskite solar cells are known as narrow band-gap solar cells which is expected to give higher efficiency than Pb perovskite solar cells from the view point of the narrow band gap energy, and is to be useful for the bottom layer for all-perovskite-tandem solar cells. We have already reported 20.4% efficiency for SnPb perovskite solar cells (1-3) and SnGe perovskite solar cells with 7.9% efficiency (4,5). There are some items which limit the enhancement of the efficiency. In this report, one of which, relationship between lattice strain and the efficiency is discussed. In the composition of QFAMASnI3, Q was changed with Na+, K+, Cs+, Ethylammonium+(EA) and Butylammonium+ (BA) respectively, and the relationship between the lattice strain obtained from XRD and the photovoltaic performances were discussed. The efficiency of the solar cells with the Sn-perovskite solar cell had linear relationship with the relative lattice strain. Among them, EAFAMASnI3 having least lattice strain gave the results of 7.6 %. The second item is trap distribution. The distribution of trap states within perovskite vicinity or hetero-interfaces is attributed to the low photovoltaic performances. Thermally stimulated current (TSC) was used for the evaluation of the trap states. The addition of 5 mole% germanium into the FAMASnI3 (FMSGI) suppressed the trap density from 1015-1017 cm-3 (without Ge) to 108-1014 cm-3 and gave longer charge diffusion length (~1 μm) to give 7.9% efficiency. In addition, on the SnPb perovskite solar cells, the relationship between the lattice strain and efficiency was discussed. By decreasing the lattice strain, the efficiency was enhanced to > 20%.

15:30 - 15:45
Mahata, Arup
Istituto Italiano di Tecnologia (IIT), Genova, Italy
Band Alignment and Polaron Formation in 2D/3D Perovskites and Mixed Pb/Sn 3D Perovskites
Arup Mahata
Istituto Italiano di Tecnologia (IIT), Genova, Italy, IT
Arup Mahata b, Daniele Meggiolaro b, Filippo De Angelis b
a, Computational Laboratory for Hybrid/Organic Photovoltaic (CLHYO), Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR), Via Elce di Sotto 8, 06123 Perugia, Italy
b, Istituto Italiano di Tecnologia (IIT), Genova, Italy, Via Morego, 30, Genova, IT

Lead halide perovskites are outstanding materials for photovoltaics due to their high efficiencies in solar cells devices. The origin of the long carrier-lifetime in this class of materials is still under debate and, among different hypothesis, the formation of large polarons preventing the recombination of charge couples is one of the most fascinating. In this work, we report a systematic study of the polaron formation process in metal halides perovskites focusing on the influence of the chemical composition of the perovskite on the polaron stabilization energy. We have investigated i) the role of the halide through the analysis of the polarons in iodide and bromide perovskites; ii) the effects of the Sn-doping in mixed and pure metal phases and iii) the indirect effects associated with the cation size and cation’s orientation in the lattice. Our study reveals that polaron formation is promoted by the bond asymmetry, with larger stabilization energies in bromide and low concentration Sn-doped perovskites compared to pure lead / tin iodide perovskites. Other factors like octahedral tilting, the size of organic cations (MA vs. FA) and their orientation in the space, i.e. dipoles, seem to play only a limited role in the process.

15:45 - 16:00
Rakocevic, Lucija
imec (partner in Solliance & EnergyVille), Kapeldreef 75, Leuven, 3001, Belgium.
Reliable comparison of perovskite solar cell performance using maximum power point tracking
Lucija Rakocevic
imec (partner in Solliance & EnergyVille), Kapeldreef 75, Leuven, 3001, Belgium.
Lucija Rakocevic a, b, Felix Ernst a, c, Robert Gehlhaar a, Tom Aernouts a, Christoph Brabec c, Jef Poortmans a, b, d
a, IMEC, Leuven, Leuven, BE
b, ESAT, KUL, Leuven, 3000, Belgium
c, Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander Universität Erlangen-Nürnberg, Martensstr. 7, 91058 Erlangen, Germany
d, University of Hasselt, 3590 Diepenbeek, Belgium

Organometallic halide based thin film PV has achieved research device efficiencies of 23.7 %, surpassing other thin film PV technologies in less than a decade of research. However, hysteretic behavior caused by ion movement in perovskite semiconductor affecting charge carrier extraction can inhibit a reliable performance measurement. This behavior, reflected in transient current variations following voltage alteration, can be dependent on preconditioning of the sample, scan rate, temperature and the composition of the perovskite solar cell stack itself.

Therefore, a reliable performance comparison of perovskite solar cells is non-trivial. We examine the robustness of maximum power point tracking (MPPT) using three measurement algorithms to compare the performance of three n-i-p planar perovskite stacks. Moreover, we extract the relevant measurement parameters for a reliable MPPT. Figure shows how the measurement delay affects the measured performance of a solar cell for each of the studied algorithms.

As the result of the study, we propose a measurement protocol to determine the device PCE applicable in everyday laboratory testing of perovskite solar cells. Finally, we draw attention to the importance of defining a robust and universal measurement procedure for comparison of various perovskite based thin film PV devices researched in the community.

16:00 - 16:30
Coffee Break
16:30 - 17:00
Barolo, Claudia
University of Turin
Near Infra-Red Dyes in Dye-Sensitized Solar Cells: from Panchromatic Absorption to Completely Transparent DSSCs
Claudia Barolo
University of Turin
Nadia Barbero a, Raffaele Borrelli b, Vittoria Novelli c, Simone Galliano a, Matteo Bonomo a, Guido Viscardi a, Claudia Barolo a, d, Frederic Sauvage c
a, Dipartimento di Chimica, NIS Interdepartmental and INSTM Reference Centre, Università degli Studi di Torino, Via Pietro Giuria 7, 10125 Torino, Italy
b, Dipartimento di Scienze Agrarie Forestali e Alimentari, Università degli Studi di Torino, Largo Paolo Braccini 2, 10095 Grugliasco, Italy
c, Laboratoire de Réactivité et Chimie des Solides, CNRS UMR7314, Université de Picardie Jules Verne, 33 Rue St-Leu, 80039 Amiens, Cedex, France
d, ICxT Interdepartmental Centre Università degli Studi di Torino, Lungo Dora Siena 100, 10153 Torino, Italy

Nowadays, most photovoltaic (PV) technologies absorb the visible domain of the light spectrum. As a consequence, these devices are not transparent or at least semi-transparent. In this contest, far-red/near infra-red (NIR) light is indubitably interesting to widen solar harvesting corresponding to 25% of overall solar light available on earth’s surface. The photoconversion efficiency expected by the exploitation of these frequencies (700-1000 nm) is lower with respect to the visible region, but, far red-NIR sensitizers allow to tune the colors of final devices from blue to green, or even to colorless. Transparent cells without any coloration would allow the visible light to pass through unhampered reaching a fully integration of PV devices in building-integrated applications (BIPV). [1]

The photosensitizer has a crucial role in a NIR-DSSC system. Different families of NIR chromophores have been investigated for applications in DSSCs with relatively low success in terms of transparency and power conversion efficiency. At present, NIR-based DSSCs exhibited at best 2.3% PCE with very thick electrodes sensitized with a cyanine dye absorbing at 805 nm. [2]. Our research group developed several squaraine dyes for DSSC absorbing in the NIR region. [3,4]

Recently a few series of new efficient all organic polymethine sensitizers based on squaraine [5], cyanine and croconine moieties with a shifted absorption as high as 830 nm have been synthesized and fully characterized. DSSCs based on these new efficient sensitizers are able to convert up to 36% IPCE until 850 nm. Their light-to-electricity performances have been optimized by using highly diluted dye solution to promote the formation of a free self-assembled monolayer.

17:00 - 17:15
Tessore, Francesca
Università di Milano
High-potential Porphyrin-based SnO2 Photoanodes for Water Photooxidation
Francesca Tessore
Università di Milano, IT
Francesca Tessore a, Gabriele Di Carlo a, Alessio Orbelli Biroli b, Elisabetta Benazzi c, Stefano Caramori c
a, Dipartimento di Chimica, Università degli Studi di Milano
b, Istituto di Scienze e Tecnologie Molecolari del CNR (CNR-ISTM), via Golgi, 19, Milan, 20133, IT
c, University of Ferrara, Italy, Via Fossato di Mortara, 17, Ferrara, IT

Porphyrins are very promising light harvesters for molecular water splitting (WS) [1-3], due to the strong UV-Vis absorptions, the high electrochemical and photochemical stability, the electronic properties which can be tuned quite easily through appropriate structural modifications [4-6]. A well-established approach for the preparation of porphyrins with potential high enough to allow water oxidation is to endow the macrocycle with electron-withdrawing groups, to induce an electron deficiency that leads to a positive shift in the ground state oxidation potential, so that the holes remaining on the photooxidized porphyrin are thermodynamically capable of driving water oxidation [3].

We have prepared some ß-substituted A4-type and meso-substituted A3B- type ZnII porphyrins, carrying pentafluorophenyl moieties and different pi-spacers and anchoring groups. The compounds have a calculated HOMO-LUMO energy gap of ∼2.2 eV with a E0red/E0ox potential of ∼0.7-0.8 V (vs Fc+/Fc), and they have been used to sensitize wide band-gap semiconductors, i.e. TiO2 and SnO2.

A detailed photoelectrochemical characterization of the photoanodes has been carried out, evaluating their performances with hydrobromic and ascorbic acid as sacrificial agents, in order to explore the electronic transfer ability of the dyes in the absence of kinetic barriers which can limit the dye regeneration. The most performing photoanode with respect to charge separation and collection has been functionalized with the efficient binuclear iridium(IV) catalyst reported by Brudvig [7], demonstrating the ability of the substrate to carry out water oxidation, and showing photoinduced production of oxygen with a Faradaic yield equal to 90%.  


17:15 - 17:30
Oskam, Gerko
Photoelectrochemistry of Semiconducting Oxide Materials for Solar Water Splitting: Characterization of Charge Carrier Dynamics Using IMPS
Gerko Oskam
Ingrid Rodríguez-Gutiérrez a, Manuel Rodríguez-Pérez b, Alberto Vega-Poot a, Geonel Rodríguez-Gattorno a, Gerko Oskam a
a, Department of Applied Physics, CINVESTAV-IPN, Mérida, Yuc., México.
b, Facultad de Ingeniería, Universidad Autónoma de Campeche, Campeche, Cam., México.

Photoelectrochemical water splitting is an attractive method to convert solar energy to storable chemical energy in the form of hydrogen. In order to efficiently convert sunlight to hydrogen, the semiconducting material must absorb sunlight efficiently, must be capable of reducing and/or oxidizing water, and has to be stable under illumination under current flow in an aqueous electrolyte solution. In particular, for small bandgap semiconductors, stability is often an issue, and it is difficult to fully avoid degradation processes. In addition, the water reduction and oxidation processes need to effectively compete with recombination and surface degradation processes. The kinetic rate constants for charge transfer and surface recombination therefore are very important parameters. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful option to study the carrier dynamics in a photoelectrochemical cell. The frequency-dependent photocurrent admittance corresponds to the frequency-dependent external quantum efficiency, and time constants for charge transfer and surface recombination can be determined, provided a simple model can be applied [1].

We have used IMPS to study the charge transfer and recombination dynamics in a variety of systems including WO3, p-CuBi2O4 and WO3-BiVO4 heterojunctions. For CuBi2O4 photocathodes, an unfavorable balance between the rate constants for charge transfer and surface recombination limits the conversion efficiency [2]. On the other hand, IMPS analysis of screen-printed WO3 photoanodes shows that the recombination rate constant is significantly smaller than the charge transfer rate constant. The efficiency  limiting process appears to be the charge collection efficiency [3]. Recent results on WO3-BiVO4 heterojunctions, CuWO4, and electrocatalyzed Sn-doped Fe2O3 photoanodes are also discussed.

19:30 - 22:00
Social Dinner
Wed May 15 2019
08:45 - 09:00
Poster prize ceremony and HOPV20 presentation
Session G3.1
Chair: Aldo Di Carlo
09:00 - 09:45
Zhu, Xiaoyang
Columbia University
Ferroelectric large polarons in lead halide perovskites
Xiaoyang Zhu
Columbia University, US

Xiaoyang Zhu is the Howard Family Professor of Nanoscience and a Professor of Chemistry at Columbia University. He received a BS degree from Fudan University in 1984 and a PhD from the University of Texas at Austin in 1989. After postdoctoral research with Gerhard Ertl at the Fritz-Haber-Institute, he joined the faculty at Southern Illinois University as an Assistant Professor in 1993. In 1997, he moved to the University of Minnesota as a tenured Associate Professor, later a Full Professor, and a Merck endowed professor. In 2009, he returned to the University of Texas at Austin as the Vauquelin Regents Professor and served as directors of the DOE Energy Frontier Research Center (EFRC) and the Center for Materials Chemistry. In 2013, he moved to Columbia University. His honors include a Dreyfus New Faculty Award from Dreyfus Foundation, a Cottrell Scholar Award from Research Corporation, a Friedrich Wilhelm Bessel Award from the Humboldt Foundation, a Fellow of the American Physical Society, a Vannevar Bush Faculty Fellow Award from DOD, and an Ahmed Zewail Award from the American Chemical Society. Among his professional activities, he serves on the editorial/advisory boards of Accounts of Chemical Research, Science Advances, Chemical Physics, and Progress in Surface Science, and as a scientific advisor to the Fritz-Haber-Institute of the Max-Planck Society and ShanghaiTech University

Xiaoyang Zhu a
a, Department of Chemistry, Columbia University, New York, New York 10027, United States

Lead halide perovskites have been demonstrated as high performance materials in solar cells and light-emitting devices. These materials are characterized by coherent band transport expected from crystalline semiconductors, but dielectric responses and phonon dynamics typical of liquids. Here we explain the essential physics in this class of materials based their dielectric functions or dynamic symmetry breaking on microscopic level [1]. We show that the dielectric function of a hybrid organic-inorganic lead halide perovskite (LHP) possesses combined characteristics of a polar liquid and a ferroelectric material. The latter response in the THz region may lead to dynamic and local ordering of polar nano domains by an extra electron or hole, resulting a quasiparticle which we call a ferroelectric large polaron, a concept similar to solvation in chemistry. Compared to a conventional large polaron, the collective nature of polarization in a ferroelectric large polaron may give rise to order(s)-of-magnitude larger reduction in the Coulomb potential and introduce potential barriers to charge carrier scattering. The ferroelectric large polaron may explain the defect tolerance and low recombination rates of charge carriers in lead halide perovskites, as well as providing a design principle for high performance semiconductors from nano, molecular, and hybrid materials.

09:45 - 10:15
Lifshitz, Efrat
Technion - Israel Institute of Technology
Magnetic Interactions in Pristine and Magnetically Doped Halide-Perovskites
Efrat Lifshitz
Technion - Israel Institute of Technology, IL
Efrat Lifshitz a
a, Schulich Faculty of Chemistry, Russell Berrie Nanotechnology Institute, Solid State Institute, Technion-Israel Institute of Technology

Magnetic interactions in pristine and magnetically doped halide-perovskites

Efrat Lifshitz, Alyssa Kostadinov and Arthur Shapiro, Technion – Israel Institute of Technology, Haifa, Israel; Maryna Bodnarchuk, Maksym Kovalenko, ETH, Zurich, Switzerland; Liang Tan, Andrew Rappe, Pennsylvania University, Philadelphia, USA. (

organic-inorganic perovskites have become one of the most promising materials in various opto-electronic applications. The best performance was found in compounds with general chemical formula, ABX3, when A is either organic or inorganic cation, like methylammonium (MA+), formamidinium (FA+) or Cs+, B is a bivalent metal cation, such as Pb2+or Sn+2 and X is a halide, Cl−, Br−, or I−. Those compounds can be further modified by a post treatment which exchange small percent of the halide anions, as well as a few metal cations with magnetic dopants. Mixed composition renders new properties beyond those of the pristine compounds.

present work describes magnetic properties in pristine and magnetically doped Cs (MA) PbBr3 perovskites produced as nanocubes or as bulk crystals. pristine perovskites were synthesized at the ETH laboratory, while the mixed halide compounds or/and magnetically doped derivatives were recently prepared at the Technion. study focused on the investigation of magneto-optical properties of the discussed compounds, via examination of polarized magneto-photoluminescence or optically detected magnetic resonance spectroscopy. The pristine perovskites exhibit linear and circular polarized emission at any magnetic field up to 8 Tesla, with a field dependence that deviates from a Zeeman-effect. A theoretical work (carried out by the Rappe group) corroborated the occurrence of a Rashba-effect stimulated by the dynamic liability of the counter ions, Cs or MA and the consequence breaking of inversion of symmetry. Furthermore, the observations indicated the occurrence of an additional magnetic phenomenon, related to nuclear spin polarization induced by the formation of an exciton (the so-called Overhouser effect), and mainly associated with intrinsic neutral abundance of the Pb metal isotope.

The magnetically doped derivatives of halide perovskites included partial dual exchange of halide and metal cations: Br was exchanged with Cl and Pb was exchanged in a limited fashion with isovalent Ni cations, the last including unpaired spins. The magnetic resonance measurement designated the integration of Ni at substitutional position with a characteristic hyperfine interactions. Thus, magnetic dopants produce additional internal magnetic coupling between photo-generated specie and guest electron and nuclear spins.

10:15 - 10:45
Kamat, Prashant
University of Notre Dame
Halide Ion Migration in Mixed Halide Lead Perovskites
Prashant Kamat
University of Notre Dame, US

Prashant V. Kamat is a Professor of Chemistry & Biochemistry, Senior Scientist at Radiation Laboratory, and Concurrent Professor of Department of Chemical and Biomolecular Engineering, University of Notre Dame. He earned his doctoral degree (1979) in Physical Chemistry from the Bombay University, and postdoctoral research at Boston University (1979-1981) and University of Texas at Austin (1981-1983). He joined Notre Dame in 1983 and initiated the project on utilizing semiconductor nanostructures for light energy conversion. His major research interests are in three areas : (1) catalytic reactions using semiconductor and metal nanoparticles, nanostructures and nanocomposites, (2) develop advanced materials such as inorganic-organic hybrid assemblies for energy conversion, and (3) environmental remediation using advanced oxidation processes and chemical sensors. He is currently serving as a Deputy Editor of Journal of Physical Chemistry Letters and A/B/C and a member of the advisory board of scientific journals, Langmuir, Research on Chemical Intermediates, Electrochemistry and Solid State Letters, and Interface. He has written more than 400 peer-reviewed journal papers, review articles and book chapters with more than 40000 citations and carries an h-index of 109. He has edited two books in the area of nanoscale materials. He was a fellow of Japan Society for Promotion of Science during 1997 and 2003 and was awarded Honda-Fujishima Lectureship award by the Japanese Photochemical Society in 2006 and Langmuir Lectureship Award in 2012. He is a Fellow of the Electrochemical Society, American Chemical Society and AAAS.

Prashant V. Kamat a, b, Rebecca Scheidt a, b, Gergely Samu a, b, Csaba Janaky a, b
a, University of Notre Dame, Notre Dame, Indiana 46556, EE. UU., Notre Dame, US
b, Department of Physical Chemistry and Materials Science, University of Sezged, Szeged, HUNGARY

Mixed halide lead perovskites are good candidates for designing tandem solar cells because one can tune the bandgap by varying halide ion composition. For example, by varying the iodide/bromide composition (CH3NH3PbBrxI3-x (x=0 to 3)) it is possible to tune the bandgap between 1.55 eV and 2.43 eV. Of particular interest are the composition dependent absorption and emission properties. The halide ions are mobile both in the dark as well as under light irradiation. The photoluminescence and absorption spectra offer a convenient means to track the movement of halide ions. By employing gradient and homogeneous films of mixed halide perovskites we have probed the movement of iodide ions and factors influencing their mobility.  The effect of halide ion segregation on the photovoltaic properties will also be discussed.

1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

10:45 - 11:15
Coffee Break
Session G 3.2
Chair: Efrat Lifshitz
11:15 - 11:45
Durrant, James
Imperial College London and Swansea University
Charge Carrier Dynamics in Disordered Materials for Solar Energy Conversion
James Durrant
Imperial College London and Swansea University, GB

James Durrant is Professor of Photochemistry in the Department of Chemistry, Imperial College London and Ser Cymru Solar Professor, University of Swansea. His research addresses the photochemistry of new materials for solar energy conversion targeting both solar cells (photovoltaics) and solar to fuel (i.e.: artificial photosynthesis. It is based around employing transient optical and optoelectronic techniques to address materials function, and thereby elucidate design principles which enable technological development. His group is currently addressing the development and functional characterisation of organic solar cells and photoelectrodes for solar fuel generation. More widely, he leads the UK�s Solar Fuels Network and the Welsh government funded S�r Cymru Solar initiative. He has published over 300 research papers and 5 patents, and was recently awarded the 2012 Tilden Prize by the RSC.

James Durrant a
a, Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London, GB


The kinetics of charge generation, separation and recombination are critical to the function of organic and perovskite solar cells and to photoelectrochemical water splitting. In my talk, I will address some of the factors determining these kinetics in these systems and how these impact upon device performance. Experimentally my talk will be based on the results of transient optical and optoelectronic measurements of both materials and devices. In organic solar cells, I will focus on a comparison of the kinetics of fullerene and non-fullerene acceptors, and the role of interfacial charge transfer states in limiting performance. For perovskite solar cells, I will focus on interfacial charge transfer and recombination in planar p-i-n MAPI3 based devices, and the impact of ion migration upon these kinetics. For photoelectrochemical water splitting, I will focus on the impact of space charge layers and junctions in separating charges.  The impact of tail states on charge carrier trapping and recombination, and thus on device performance, and the energetic cost of lifetime gain will recurring topics. Throughout my talk, I will try to highlight the similarities and difference between these materials and technologies, and the insights which can be learnt from comparison between these systems.


11:45 - 12:15
Prezhdo, Oleg
University of Southern California
Time-Domain Modeling of Excited State Dynamics in Halide Perovskites
Oleg Prezhdo
University of Southern California

1993-1997 PhD, U Texas at Austin 1997-1998 Postdoc, Yale U 1998-2010 Prof, U Washington at Seattle 2010-2014 Prof, U Rochester, NY 2014-current Prof. U. Southern California

Oleg Prezhdo a
a, Chemistry, University of Southern California, 3620 McClintock Ave, LA, CA, US

Photo-induced processes play key roles in photovoltaic and photo-catalytic applications of halide perovskites, requiring understanding of the material’s dynamical response to the photo-excitation on atomic and nanometer scales. Our non-adiabatic molecular dynamics techniques,1 implemented within time-dependent density functional theory,2-4 allow us to model such non-equilibrium response in the time domain and at the atomistic level. The talk will focus on photo-initiated energy and charge transfer, relaxation and recombination in hybrid organic-inorganic perovskites. Considering realistic aspects of perovskite structure,5 we demonstrate that strong interaction at the perovskite/TiO2 interface facilitates ultrafast charge separation,6 how dopants can be used to both decrease and increase charge recombination,7-9 that grain boundaries constitute a major reason for charge losses,9 that moderate humidity increases charge lifetime, while high humidity accelerates losses,10 that hole trapping by iodine interstitial, surprisingly, extends carrier lifetime,11 that collective nature of dipole motions inhibits nonradiative relaxation,12 that organic cation orientation has a strong effect on inorganic ion diffusion and current-voltage hysteresis,13 that surface passivation with Lewis base molecules decelerates nonradiative charge recombination by an order of magnitude,14 that the experimentally observed dual (hot/cold) fluorescence originates from two types of perovskites substructures,15 that doping with larger cations increases lattice stiffness and slows down nonradiative charge recombination,16 why PbI2 rich perovskites show better performance,17 that halide composition can be used to control charge relaxation,18 that oxidation states of halide defects strongly influence charge trapping and recombination,19 and why perovskites exhibit unusual temperature dependence of electron and hole lifetimes.20

12:15 - 12:45
Stranks, Samuel D.
University of Cambridge - UK
Visualising the Impact of Defects and Strain on Halide Perovskite Structures
Samuel D. Stranks
University of Cambridge - UK, GB
Samuel Stranks a
a, Cavendish Laboratory, Department of Physics, University of Cambridge, UK, JJ Thomson Avenue, Cambridge, GB

Halide perovskites are exciting materials for a range of optoelectronic devices. One of their most tantalizing features is the potential for tunable emission with high luminescence yields. Such properties are promising for reaching the radiative efficiency limits in single and multi-junction solar cells as well as color-tunable light-emitting diodes. However, there are a number of challenges in mitigating all defects in order to attain high luminescence yields and color stability across a range of bandgaps.

Here I will present a selection of our group’s ongoing work to understand the nature of defects leading to non-radiative power losses in a range of halide perovskite films, crystals and device systems, and how we can use this information to push materials and devices towards their efficiency limits. We use a selection of nano- and micro-scale imaging techniques including photoluminescence, photo-emission and nano-X-Ray-Diffraction microscopy to visualise the impact of defects and strain on local charge carrier recombination. We also employ passivation techniques designed to remove these spatially heterogeneous losses, which we demonstrate on a variety of systems. Finally, we show that these approaches ultimately lead to tangible improvements in solar cell and LED performance and bandgap stability.

12:45 - 13:15
Berry, Joseph
Chemistry and Nanoscience Center, National Renewable Energy Laboratory
Pathway to Halide Perovskite Photovoltaics: Two Recent Advances in All Perovksite Tandems
Joseph Berry
Chemistry and Nanoscience Center, National Renewable Energy Laboratory, US
Joseph Berry a
a, Chemistry and Nanoscience National Renewable Energy Laboratory

Photovoltaic devices based on hybrid organic-inorganic perovskite absorbers have reached outstanding performance over the past few years, surpassing power conversion efficiency of over 23% for single junction and present multiple paths to tandems with efficiencies beyond 30%.  This talk will discuss recent progress and challenges in hybrid perovskite solar cells (HPSCs) with an emphasis on the role of materials integration challenges needed to enable device performance, tandem processing and stability.  Specifically, this talk will highlight recent progress at NREL, the challenges of tandems based on HPSC devices, and work to develop scalable HPSCs approaches for tandem and single junction systems. Details of material formation, the resulting interfaces and the role of processing in creating efficient device stacks, critical to high-volume manufacturing will be touched upon.  Our studies at NREL indicate formation dynamics for the active layer and interface to the contacts directly impacts the ability to create efficient stable devices and enable tandems from common (i.e. nonorthogonal) solvents.  Advanced concepts to improve low and wide bandgap HPSC systems critical to enabling tandems will also be presented. Data on the optoelectronic material and system properties as characterized by an array of analytical tools including time resolved spectroscopy, structural studies and device level evaluation will be presented to validate the technological relevance of advances and suggest overarching themes for research directions.

13:15 - 14:30
Lunch Break
Session A3
Chair: Francisco Fabregat-Santiago
14:30 - 15:00
djurisic, aleksandra
university of hong kong
Towards Improved Stability of Organic-Inorganic Perovskite Solar Cells
aleksandra djurisic
university of hong kong
Aleksandra Djurisic a, Fangzhou Liu a, Ho Won Tam a, Tik Lun Leung a
a, Department of Physics, The University of Hong Kong, Rm 314, Chong Yuet Ming Physics Building, The University of Hong Kong, Pokfulam Road

The efficiency of perovskite solar cells (PSCs) has been rapidly increasing since the first reports on the solid state devices in 2012, and the current record efficiency of 23.3% exceeds that of more mature technologies, such as CIGS and CdTe. However, the device stability remains a significant concern, and further improvements both in stability achieved as well as standardization of reported measurement protocols and results are needed for future commercialization of this technology. Therefore, we will discuss the degradation mechanisms in perovskite thin films and devices, with the emphasis on the effect of perovskite layer composition and deposition method on the film and device stability. The perovskite film composition, and consequently its photovoltaic performance and stability are strongly dependent on the deposition conditions. Next, we will discuss the effects of encapsulation on the device stability, which will include performance upon water immersion as well as standardized accelerated aging and outdoor testing according to ISOS protocols. Encapsulation protocols will be discussed for both rigid and flexible substrates. The efficiency of perovskite solar cells (PSCs) has been rapidly increasing since the first reports on the solid state devices in 2012, and the current record efficiency of 23.3% exceeds that of more mature technologies, such as CIGS and CdTe. However, the device stability remains a significant concern, and further improvements both in stability achieved as well as standardization of reported measurement protocols and results are needed for future commercialization of this technology. Therefore, we will discuss the degradation mechanisms in perovskite thin films and devices, with the emphasis on the effect of perovskite layer composition and deposition method on the film and device stability. The perovskite film composition, and consequently its photovoltaic performance and stability are strongly dependent on the deposition conditions. Next, we will discuss the effects of encapsulation on the device stability, which will include performance upon water immersion as well as standardized accelerated aging and outdoor testing according to ISOS protocols. Encapsulation protocols will be discussed for both rigid and flexible substrates.

15:00 - 15:15
Hossain, Ihteaz Muhaimeen
Institute of Microstructure Technology, Karlsruhe Institute of Technology
Nanophotonic Front Electrodes for Perovskite-based Tandem Photovoltaics
Ihteaz Muhaimeen Hossain
Institute of Microstructure Technology, Karlsruhe Institute of Technology, DE
Ihteaz Muhaimeen Hossain a, b, Yidenekachew Donie a, b, Raphael Schmager a, Mohamed S. Abdelkhalik a, Andrei Karabanov a, Somayeh Moghadamzadeh b, Jonas A. Schwenzer b, Uli Lemmer a, b, Bryce S. Richards a, b, Guillaume Gomard a, b, Ulrich W. Paetzold a, b
a, Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
b, Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany

The unprecedented growth of perovskite solar cells (PSCs) during the last decade made perovskite photovoltaics a competitive technology as the power conversion efficiencies (PCEs) reach staggering values close to 24%. Very recently, it was also demonstrated that in conjunction with Si in 4-terminal architecture, the tandem PCE stretched out to 28%, exceeding the PCE of single junction Si PV already today.

One prominent factor that still limits the PCE of state-of-the-art perovskite tandem PV is the imperfect transmission of the incident light below the bandgap of the perovskite top cell into the Si bottom solar cell. In order to explore this, the transmission at the front interfaces of the perovskite top solar cell must be increased. In this work, we develop polymer nanopillars embedded in an indium-doped tin oxide (ITO) layer to form front electrodes with enhanced optical transmittance. The polymer blend lithography process is used to control the morphology of the self-assembled nanopillars, prior to ITO deposition. In comparison to planar ITO, nanopillar front ITO improves the transmission over a broad wavelength range (absolute ~5%). The continuous change in the effective refractive index due to structuring allows reduction of reflection at the nanopillar/ITO and ITO/air interface and enhances the overall transmission.

Our initial findings using optical characterization on a layer stack of PSC (glass/nanopillar ITO/SnO2/Perovskite/Spiro-OMeTAD) suggest an improved transmission below the bandgap of the perovskite. This means, that fabrication of semi-transparent PSCs with these nanostructured front ITO would result in better light transmission from semi-transparent PSC for more efficient Perovskite/Si or Perovskite/CIGS tandem solar cells.

15:15 - 15:30
Winkler, Kristina
Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse 2, 79110 Freiburg, Germany
Monolithic perovskite silicon tandem solar cells with high-bandgap perovskite absorber exceeding 1.8 V open-circuit voltage
Kristina Winkler
Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse 2, 79110 Freiburg, Germany
Alexander J. Bett a, Patricia S.C. Schulze a, Kristina M. Winkler a, Özde Kabakli a, Martin Bivour a, Ludmila Cojocaru b, Ines Ketterer a, Laura E. Mundt a, Leonard Tutsch a, Martin Hermle a, Stefan W. Glunz a, b, Jan Christoph Goldschmidt a
a, Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse 2, 79110 Freiburg, Germany
b, Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), Laboratory for Photovoltaic Energy Conversion, Department of Sustainable Systems Engineering (INATECH), University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany

Perovskite silicon tandem solar cells have the potential to overcome the efficiency limit of 29.4% [1] of single junction silicon solar cells by reduction of thermalisation losses. In particular, we aim for monolithic tandem devices as it requires a lower number of transversely conductive layers and allows for more facile module integration compared to 4-terminal devices.

We use an n-type heterojunction silicon bottom solar cell with a pyramidal rear side texture. On both sides an intrinsic amorphous silicon layer is deposited by plasma enhanced chemical vapour deposition (PECVD) followed by a p doped and n doped amorphous silicon layer on the front and rear side, respectively. This silicon solar cell exhibits an implied open-circuit voltage (VOC) of over 700 mV. A perovskite top solar cell with regular n-i-p architecture is connected to the bottom solar cell via an indium doped tin oxide (ITO) recombination layer. To prevent degradation of the bottom solar cell, a low-temperature process is deployed for the top cell. As an electron contact we use evaporated compact TiO2 and a UV-treated mesoporous TiO2 scaffold [2]. Subsequently, a passivation layer of PCBM and PMMA is spin coated [3] followed by deposition of the stable mixed cation mixed halide perovskite FA0.75Cs0.25Pb(I0.8Br0.2)3 with an optical bandgap of 1.7 eV, which is in the optimal range for monolithic silicon-based tandem devices [4]. The front contact consists of Spiro-OMeTAD and directly sputtered ITO (sheet resistance 44 Ohm/sq). As we use a soft ITO deposition process no additional buffer layer is needed. Finally, a MgF2 antireflection coating was evaporated. The thicknesses of ITO and MgF2 have been optimized in order to achieve highest transmission. The perovskite top solar cells reach VOC values of ~1150 mV.

Our tandem devices achieve very high VOC values of >1.8 V and power conversion efficiencies (PCE) over 20% with negligible hysteresis on a defined cell area of 0.25 cm². The champion device exhibits over 21% PCE measured under 1 sun illumination at fixed maximum power point voltage for 30 min in ambient air.

The remarkably high VOC values exceed the VOC of recent record efficiency devices [5]. The slightly lower PCE is due to the Spiro-OMeTAD hole transport layer: parasitic absorption and the inappropriate refractive index causing reflection losses limit the short-circuit current of our devices. To overcome this limitation, we investigate alternative hole transport materials.

15:30 - 15:45
Razera, Ricardo
Stability of Perovskite and Two Terminal Si/perovskite Tandem Solar Cells under Reverse Bias
Ricardo Razera
Ricardo Razera a, c, Peter Fiala a, Fan Fu a, Florent Sahli a, Terry Yang a, Matthias Bräuninger a, Henri Boudinov c, Quentin Jeangros a, Christophe Ballif a, b
a, Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, Lausanne, CH
b, Swiss Center for Electronics and Microtechnology (CSEM), PV Center, Rue Jaquet-Droz 1, 2000 Neuchâtel, Switzerland
c, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500. Room: M215, 43.133, Porto Alegre, 91501

A well-known module reliability issue in crystalline-silicon photovoltaics arises when a shaded cell is driven into reverse bias by illuminated cells connected in series [1]. In this case, the shaded cell may dissipate a substantial amount of power, which can create hot spots and irreversibly damage the cell or encapsulant. This problem is even more severe for perovskite solar cells. It has been demonstrated [2] that, even in the absence of hot spot formation, such cells can degrade simply from being subjected to a few minutes of reverse bias. This degradation was suggested to be caused by an electrochemical reaction that occurs between mobile ions inside the perovskite and the adjacent layers, although only indirect evidence was given [2]. It also remains to be analyzed how the problem may manifest itself in monolithic perovskite/c-Si tandem cells, particularly when illuminated by different spectra and intensities. Here we investigate this instability further by using microstructural analysis techniques to determine the distribution of ions in degraded cells with different compositions and with different contact layers, both in single-junction and in tandem structures. We also analyze the requirements the cell must meet to be considered stable under reverse bias, taking into account the possibility of adding bypass diodes to the module.

15:45 - 16:00
Belisle, Rebecca
Wellesley College
Designing Contact Layers and Surface Treatments to Overcome Performance Challenges for Perovskite Tandems
Rebecca Belisle
Wellesley College, US
Rebecca Belisle a, James Raiford b, Kevin Bush c, Luca Bertoluzzi c, Aryeh Gold-Parker d, f, Axel Palmstrom b, Rohit Prasanna e, Michael Toney f, Stacey Bent b, Michael McGehee e
a, Department of Physics, Wellesley College
b, Department of Chemical Engineering, Stanford University
c, Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, McCullough Building, Stanford, US
d, Department of Chemistry, Stanford University, Stanford, 94305, US
e, Department of Chemical and Biological Engineering, University of Colorado Boulder
f, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory Menlo Park, 94025, US

Perovskite tandems have come to the fore as highly promising photovoltaic technologies. However, in order for these solar cells to reach their high-efficiency potential, some significant performance challenges must first be overcome. Namely, we must reduce the parasitic absorption in contact-layers that substantially reduces the short-circuit current of perovskite tandems, and we must understand and prevent the photo-induced phase segregation in high-bandgap perovskites that limits the open-circuit voltage of these devices. In this talk, we will share our results addressing these two challenges through the design and characterization of contact layers and surface treatments for perovskite tandems.

To mitigate losses in short-circuit current, we have developed a novel hole transport bilayer for improved photocurrent and stability in N-I-P architecture perovskite solar cells for 2-terminal tandems. By combining a thin, undoped organic small molecule and a novel air-stable vanadium oxide buffer layer deposited via atomic layer deposition (ALD), we are able to fabricate stable semi-transparent perovskite solar cells with low parasitic absorption. This reduced absorption manifests in an 2.3 mA/cm2 increase in device photocurrent when compared to controls made with the spiro-OMeTAD, and creates a pathway towards higher efficiency perovskite tandems.

However, to fully realize the potential of perovskite tandems requires improvement in the photovoltage in addition to the photocurrent, and to address present limits we again look to improvements in contact materials and surface treatments.  By varying selective-contact materials and surface chemistry we demonstrate a substantial reduction in non-radiative recombination and suppression of photo-induced halide segregation. Based on these observations, we have developed a model of phase segregation linked to electron trapping at surface states, and in light of this model we suggest a pathway towards optically-stable high bandgap perovskites. Overall, this work highlights the importance of and opportunities for the development of novel contact and interfacial layers for high efficiency perovskite tandems.  

16:00 - 16:30
Coffee Break
16:30 - 16:45
Jost, Marko
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany
Thin Conformal Hole Transport Layers Enabling Highly Efficient Monolithic Perovskite/CIGSe Tandem Solar Cells
Marko Jost
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, DE
Marko Jost a, Tobias Bertram b, Dibyashree Koushik c, Jose A. Marquez d, Marcel A. Verheijen c, Eike Köhnen a, Amran Al-Ashouri a, Thomas Unold d, Mariadriana Creatore c, Iver Lauermann b, Christian A. Kaufmann b, Rutger Schlatmann b, Steve Albrecht a
a, Young Investigator Group Perovskite Tandem Solar Cells, Helmholtz-Zentrum Berlin, Berlin, DE
b, Helmholtz-Zentrum Berlin, PVcomB, Berlin, Germany
c, Department of Applied Physics, Eindhoven University of Technology (TU/e), the Netherlands
d, Department Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, Hahn-Meitner-Platz, 1, Berlin, DE

Perovskite solar cells have lately established themselves as one of the best choices for a top cell in a monolithic tandem devices. As a bottom cell, silicon has mostly been the material of choice. Besides its high efficiency, one of the main reasons is the possibility of polishing its front side. This way wet chemical processing of very thin contact layers (<20 nm) and perovskite, to day still the most efficient way of fabricating perovskite solar cells, is feasible. On the other hand, copper indium gallium diselenide (CIGSe) solar cells were only rarely used as bottom cells due to their rough surface, with their root-mean-square roughness (σRMS) typically in the range between 50-200 nm. Here, we present highly efficient monolithic perovskite/CIGS solar cells, enabled by a conformal deposition of NiOx via atomic layer deposition (ALD) [1]. A 10 nm thick layer of NiOx is already capable of preventing shunting of the top cell. This way a PCE of 18% was measured. However, NiOx/perovskite suffers from strong recombination and consequently low VOC. By introducing an additional layer of the polymer PTAA we optimize the limiting NiOx/perovskite interface. Thus, a p-type selective contact bilayer is introduced, leading to a monolithic perovskite/CIGSe tandem device with a stabilized PCE of 21.6% in maximum power point tracking over 10 minutes. TEM and EDX measurements are carried out, confirming the conformal growth of the ALD NiOx and non‑conformal growth of spin-coated PTAA. To investigate the absorber quality of both subcells we measure absolute photoluminescence (PL) [2] on the fabricated tandem device. Calculated quasi-Fermi level splitting of the subcells match well with the VOC of the reference single‑junction devices. This indicates that lower VOC of the tandem solar cell could be improved by tailoring recombination layers between the two subcells. Our results show a way for exploiting great potential of perovskite/CIGSe.

16:45 - 17:00
Zhou, Yangying
State Key Laboratory of New Ceramics & Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
Perovskite Solar Cell-Thermoelectric Tandem System with a High Efficiency of Over 23%
Yangying Zhou
State Key Laboratory of New Ceramics & Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
Yangying Zhou a, Hong Lin a
a, State Key Laboratory of New Ceramics & Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.

Photovoltaic-thermoelectric (PV-TE) tandem system has been considered as a viable approach to fully exploit solar energy by making full use of both solar light and heat generation. Herein, we demonstrate an efficient perovskite solar cell (PSC)-thermoelectric (TE) hybrid system with four-terminal configuration. To balance the light-to-electricity and heat-to-electricity efficiency and ultimately realize highly-efficient solar energy conversion, we performed both simulation and experiment by tuning the bandgap of top perovskite solar cell. Using perovskite with a composition of CH3NH3Pb(I0.95Br0.05)3 (band gap: 1.61 eV), we achieved a state-of-the-art efficiency of over 23% in this tandem system, with 18.3% from the PSC and the remaining 4.8% contributed by heat conversion using TE module. Our work proves that the low-grade heat produced by PSCs can be recovered and utilized by thermoelectric modules, and provides a promising route to improve the utilization rate of solar radiation based on PSCs.

17:00 - 17:15
Ben Dkhil, Sadok
Dracula Technologies
Printable High Efficiency Flexible and Free Design OPV Modules for Indoor Application
Sadok Ben Dkhil
Dracula Technologies
SADOK BEN DKHIL a, Florent Pourcin a, Elena Barulina b, Pavlo Perkhun b, Olivier Margeat b, Christine Vidélot Ackermann b, Jörg Ackermann b, Jérome Vernet a, Brice Cruchon a, Pascal Pierron a
a, Dracula Technologies, 4 rue Georges Auric, 26000 Valence, France
b, Aix Marseille Univ, CNRS UMR 7325, CINaM, Marseille, France.


Over the last decade, organic solar cells (OSCs) have become a promising technology for next generation solar cells combining novel properties such as light weight, flexibility, or color design with large-scale manufacturing with low environmental impact. However, the main challenge for OSC will be the transfer from lab-scale processes to large-area industrial solar cell fabrication. High efficiencies in the field of OSCs are mainly achieved for devices fabricated under inert atmosphere using small active areas, typically below 0.2 cm2. So far, a small lab scale devices have now reached performances above 17% [1].


In this light, inkjet printed organic solar cells and modules with large area were demonstrated. Inkjet printing allows direct patterning of four layers, including the top electrode, offering full freedom of design without the use of masks or structuring by hardware. Inkjet printed large area (>1 cm2) organic solar cells with power conversion efficiency exceeding 6.5 % deposited from environmentally friendly solvents in an air atmosphere are demonstrated using the same printer. To prove the great advantage of inkjet printing as a digital technology allowing freedom of forms and designs, large area organic modules with different artistic shapes were demonstrated
keeping high performance.


The good module performance at low illumination make our OPV modules good candidates for indoor applications, field in full expansion thanks to the Internet of Things (IoT).


Reported results confirm that inkjet printing has high potential for the processing of OPV, allowing quick changes in design as well as the materials.


[1]L. Meng et al., Organic and solution-processed tandem solar cells with 17.3% efficiency, Science 10.1126/science.aat2612 (2018)


17:15 - 17:30
Wagner, Lukas
Fraunhofer ISE
The Carbon Footprint of Solar Cells: How the Ultimate Lower Limit Can Be Reached with Perovskites
Lukas Wagner
Fraunhofer ISE, DE
Lukas Wagner a, Simone Mastroianni a, Andreas Hinsch a
a, Fraunhofer-Institute for Solar Energy Systems ISE, Heidenhofstrasse 2, D–79110 Freiburg, Germany

Photovoltaics (PV) is on a transition to become a key technology in the global energy sector. Still, globally PV generates less than 2% of the electricity but is on a trajectory to reach 40% by mid-century to accomplish the Paris climate goals. It is now the time to draw attention to the impact that a global PV industry will have on the climate in the future. In this regard we present carbon emission estimates of the future PV industry. We show that, to fulfil the Paris climate goals, the global PV industry needs to grow in such a way that in any case it will have a significant share in global carbon emissions, which need to be minimized. This viewpoint represents a future oriented way of thinking about developments on photovoltaics and other global energy technologies which is not solely based on economic growth. Thereby, the integrative rationale lies in the top-down conceptualization and development of novel PV technologies from the perspective of the final product.

The lowest theoretical boundary for the carbon footprint of for grid-connected PV is represented by the concept of photovoltaic glass. We demonstrate that this limit can be closely approached by the in-situ concept for glass-frit encapsulated perovskite solar modules. Thereby, the carbon footprint can be reduced by a factor of 20 compared to silicon PV. In this regard, we span the perspective from certified record laboratory efficiency results to the implementation of the module production into the existing glass industry infrastructure.

Session B3
Chair: Samuel D. Stranks
14:30 - 14:45
Uchida, Satoshi
The University of Tokyo
High Resolution TEM Observation of MAPbI3 Perovskite Solar cells with Superlattice
Satoshi Uchida
The University of Tokyo, JP

Prof. Satoshi Uchida is a professor (born in 1965) in Research Center for Advanced Science and Technology (RCAST), The University of Tokyo.  He received his PhD from Tohoku University in 1995 and moved to current position in 2006.  For more than 15 years his research focused on the field of dye-sensitized solar cells (DSSCs), specifically cell assembling technique such as full-plastic, light-weight, film type as a ubiquitous power source.  He is now also showing strong activity of Perovskite Solar Cells research based on the crystallography, surface engineering and electronic simulation.

Tae-Woong Kim a, Ludmila Cojocaru b, Satoshi Uchida a, Tomonori Matsushita a, Takashi Kondo a, Hiroshi Segawa a
a, Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, JP
b, Laboratory for Photovoltaic Energy Conversion, University of Freiburg

The microstructural observation analysis of the perovskite layer with high resolution TEM is the most promising approach to understand the crystal structure. Recently we newly revailed that the tetragonal and cubic phases coexist at room temperature in the conventional MAPbI3 thin film device. Furthermore superlattices composed of these mixture of tetragonal and cubic planes without any compositional change was also found. Formation of the superlattice is achieved by only intrinsic structural transition without artificial modifications and, therefore, most phenomena concerned with the structural superlattice are expected to spontaneously and automatically occur in context with situation. The organometal halide perovskite self-adjusts their microstructural configuration and self-organizes buffer layers inside crystal or at hetero-interface by introducing the self-assembled superlattices.  We believe, this report will be a vital cornerstone to bring the PCEs of the organometal halide perovskite solar cells one step closer to theoretical maximum point and redefine possibility of the organometal halide perovskite as promising materials for not only solar cell but also various applications.

14:45 - 15:00
Barea, Eva
Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain
Conjugated Organic Cations to Improve the Optoelectronic Properties of 2D/3D Perovskites
Eva Barea
Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, ES
Eva M. Barea a, Jesús Rodríguez-Romero a, Bruno Clasen Hames a, Iván Mora-Seró a
a, Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, ES

Two-dimensional (2D) hybrid perovskites (HPVKs) are structures alternating organic and inorganic layers, arising from inclusion of a large organic cation providing Goldschmidt’s tolerance factor higher than 1.1 This fact generates separation of a determined number of inorganic layers (n), which can range from 1 to ∞, which corresponds to a 3D arrangement. A variation of this pure organic−inorganic structure can be obtained by addition of a small organic cation, MA (CH3NH3+) in most cases, providing a Goldschmidt’s tolerance factor adequate for perovskite formation, making it so the inorganic part becomes a hybrid structure. These organic−inorganic hybrid structures are called 2D/3D HPVKs. Actually, 2D/3D perovskite-based solar cells have emerged as an alternative to pure 3D perovskites with the aim to improve their long-term stability, which is a key factor in future device commercialization.2,3

In the last years, several studies have been reported on 2D/3D perovskites prepared using mainly two ammonium salts: (i) phenylethylammonium iodide (PEA), with 4.73% efficiency for a layered material (n = 3)4 and 15.3% for a quasi-3D material (n = 60)5 and (ii) butylammonium iodide (BAI) (4.02−12.52%), observed only in layered materials, i.e., n ≤5).6−8 Recently, 1 year stable 2D/3D perovskite-based devices fabricated using 5-ammonium valeric acid iodide with an efficiency up to 11% have been shown.2

The results obtained so far can be considered very limited because, in general, the studies have focused only on aliphatic nonconjugated ammonium salts. Although it is true that the moisture stability increases, it is also true that the photovoltaic performance of 2D/3D PVK materials is severely limited owing to quantum and dielectric confinement effects. Accordingly, it is necessary the synthesis and deep optical characterization of materials with an adequate management of dielectric contrast between the layers. In this study, we demonstrate the successful tuning of dielectric confinement by the inclusion of a conjugated molecule, anilinium cation, as a bulky cation, in the fabrication of the 2D/3D PVK material (C6H5NH3)2(CH3NH3)n-1PbnI3n+1, where n=3-5.

The absence of excitonic states related to n ≥ 1 at room temperature, as well as the very low concentration of excitons after 1 ps of excitation of samples in which n ≥ 3, provide strong evidence of an excellent ability to dissociate excitons into free charge carriers. As consequence films with low n, presenting higher stability than standard 3D perovskites, improved significantly their performance, showing one of the highest short circuit current density (Jsc=13.8) obtained to date for perovskite materials within the 2D limit (n < 10).

In this study, we demonstrate that the use of a conjugated anilinium cation, with a cloud of free and polarizable p-electrons, in the preparation of a 2D/3D PVK leads to the production of a material with improved optical and electrical properties. The determining factor is the tuning of the dielectric contrast between the inorganic and organic layers, which has a direct influence on the decrease in the exciton binding energy. Using steady-state and femtosecond time-resolved absorption experiments, we have proved the high efficiency of the dissociation of initially generated excitons, even in samples with a low n value (about 3), and thus the high potential of these structures in photovoltaics. And surprisingly, although the intrinsic nature of employed cation suggests a significant interaction with water, devices fabricated with a 2D/3D perovskite displayed higher stability (~70%) after 288 h than those based on a 3D one (<40%).

15:00 - 15:15
Alberti, Alessandra
Nitrogen soaking promotes lattice recovery in polycrystalline hybrid perovskites
Alessandra Alberti
alessandra alberti a, ioannis deretzis a, giovanni mannino a, emanuele smecca a, filippo giannazzo a, andrea listorti b, silvia colella b, sofia masi b, antonino la magna a
a, Institute for Microelectronics and Microsystems (CNR-IMM), Zona Industriale - VIII Strada 5, Catania 95121, Italy
b, Università del Salento, 1 Dipartimento di Matematica e Fisica “E. de Giorgi”, LECCE, 73100, IT

Organic-inorganic hybrid perovskites are nowadays considered as reference materials for optoelectronics and photovoltaics. Their outstanding yields in luminescence, electroluminescence and photoelectric conversions, combined with the easy solution processing, promise large-scale production, wide dissemination and high technological throughput.

However, the well-known structural instability of hybrid perovskites under working conditions limits a real market uptake of all the related technologies. Solutions to guarantee the durability of products are mandatory and can be numerous, if the problem is addressed from different perspectives. 

Moreover, the plethora of perovskite materials produced in different laboratories, with preparation procedures changing from lab to lab and from time to time, ask for stabilising  treatments that, in a certain extent, reset the starting conditions in a convenient and reproducible manner. This is particularly needed for small grained perovskite layers, on one hand used to implement pinhole-free coverages, but, on the other hand, offering extended lattice discontinuities due to the high surface to volume ratio. In addition to morphology and environment, temperature-related effects are unavoidable during device operation. A rationalization of the phenomena needs to embody heating and thermal cycles to preserve the material integrity and/or the structural reversibility vs. temperature.

In this framework and on the basis of experiment and theory, we draw a general paradigm that reconsiders N2 not simply being an inert species but rather a small effective healing gas molecule inside a MAPbI3 layer. Nitrogen is soaked into polycrystalline MAPbIvia a post-deposition mild thermal treatment under slightly overpressure conditions in order to promote its diffusion through the whole layer. We observe a significant reduction of radiative recombination and a concurrent increase of light absorption, with a maximum benefit at 80 °C. Concomitantly, the current of holes locally drawn from the surfaces by a biased a tip with nanometric resolution has increased by a factor 3 under N2. This was framed by a reduction of the barrier for the carrier extraction. The achieved improvements were linked to a nitrogen-assisted recovery of intrinsic lattice disorder at the grain shells along with a simultaneous stabilization of under-coordinated Pb2+species and MAcations through weak electrostatic interactions. Defect mitigation under Nis further supported by the behavior of the absorption coefficient during thermal cycles in comparison to similar data under Argon. We additionally unveil that surface stabilization through Nis morphology-independent and can be thus applied after any preparation procedure.

Such simple and low-cost strategy could complement other stabilizing solutions when building perovskite solar cells or light-emitting diodes.

Paper just accepted in Advanced Energy Materials




15:15 - 15:30
Gagliardi, Alessio
Technische Universitaet Muenchen
Novel Machine Learning Method for Stability and Energy Bandgap Prediction of Lead Free Perovskite Materials
Alessio Gagliardi
Technische Universitaet Muenchen, DE
Alessio Gagliardi a, Jared Stanley a
a, Technische Universität München, Karlstraße 45, München, 80333, DE

The identification of suitable lead-free perovskites is crucial for their envisioned applications in photovoltaics. Homovalent substitution of lead with Sn- and Ge-based compounds are under intense investigation as potential alternatives, but suffer from stability issues, for example, due to the susceptibility of these ions toward the 4+ oxidation state. Mixed compositions, with two or more possible ions for each lattice position, have been proposed for overcoming these issues and enhancing performance [1, 2]. However, as it is computationally and experimentally prohibitive to measure the vast configuration space available to the mixed perovskites, statistical learning techniques are needed to find a more efficient mapping of mixing parameters to the properties of interest.

Efficient and accurate vetting of perovskites for a range of properties has recently been accomplished in high-throughput Density Functional Theory (DFT) studies of compounds by use of Kernel Ridge Regression (KRR) [3, 4]. Crucial to their success is the determination of adequate material fingerprints which uniquely define the materials and capture the property of interest. Here we demonstrate how one such important screening parameter, the fundamental bandgap, can be predicted for a family of inorganic mixed halide perovskites using novel globally valid material fingerprints based solely on the atomic configurations of arbitrary unit cells. The Partial Radial Distribution Function method [5] is expanded upon to include densities for a variety of elemental properties, enabling us to define a more robust material fingerprint while illuminating the underlying drivers of target properties in a chemically intuitive manner. The results are supplemented with thermodynamic and geometric data to identify the best compositions and the features responsible for them.

15:30 - 16:00
Troshin, Pavel
Revealing Diverse Degradation Pathways in Lead Halide Perovskite Solar Cells
Pavel Troshin
Azat Akbulatov a, Olga Yamilova b, a, Mohamed Elnaggar a, b, c, Alexandra Boldyreva b, Moneim Elshobaki b, Sergey Tsarev b, Lyubov Frolova b, a, Keith Stevenson b, Pavel Troshin b, a
a, Institute for Problems of Chemical Physics of RAS, Semenov ave. 1, Chernogolovka, Moscow region, 142432, Russia.
b, Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Nobel st. 3, Moscow, RU
c, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow, Russia

The emerging perovskite solar cells demonstrated impressive power conversion efficiencies exceeding 23%, while their practical application is restricted mainly by poor operation stability. We have reported recently that hybrid MAPbX3 perovskites undergo facile thermal and photochemical degradation even under anoxic conditions without exposure to oxygen and moisture, while their all-inorganic counterparts CsPbX3 proved to be significantly more stable.

Here we will discuss our the most recent results coming from a systematic study of the intrinsic stability of a broad range of materials represented by various lead-based perovskites as well as lead-free complex halides of tin, germanium, bismuth and antimony. The revealed pathways of thermal, photochemical and electrochemical degradation processes will be presented and a conclusion on the potential of different groups of materials for practical application in PV technology will be drawn.

We will also analyze the interface degradation effects occurring between the electrodes, charge transport layer materials and the photoactive layer induced by electric field, elevated temperatures, solar light or a combination of these stress factors. Finally, it will be shown that reaching any commercially interesting operation lifetimes for perovskite solar cells requires a considerable shift from the currently used device design paradigms as well as a comprehensive multiparametric optimization of all used materials and functional components.

16:00 - 16:30
Coffee Break
16:30 - 16:45
Burgos Caminal, Andrés
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
Hot Carrier Dynamics in Lead Halide Perovskites: Mobility and Carrier-Phonon Coupling
Andrés Burgos Caminal
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH
Andrés Burgos-Caminal a, Aurélien Willauer a, Ahmad Ajdar Zadeh a, Jacques-E. Moser a
a, Photochemical Dynamics Group, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, Lausanne, CH

Time resolved terahertz spectroscopy (TRTS) is a very useful ultrafast laser spectroscopy technique for the study of charge carriers in semiconductors.[1] Its sensitivity to both carrier mobility and concentration can help elucidate the mechanisms of their temporal evolution. However, traditional techniques of THz generation and detection, such as optical rectification and electro-optic sampling, are generally limited in bandwidth and temporal resolution to <3THz and 0.5-1 ps, making the study of the early dynamics an arduous task susceptible to analysis errors due to the convolution with the instrument response function (IRF). The development of gas photonics helped to solve this problem with the generation and detection of ultra-broadband and short THz pulses, thanks to the air-biased coherent detection technique [2-3] and the use of dual color laser induced plasmas for generation.[4]

We present a study of the early charge carrier dynamics in lead halide perovskites from the point of view of THz mobility. These materials have become one of the dominant topics in solar energy research, thanks to their outstanding performance and facile processability. Taking advantage of our improved time resolution, down to 200 fs, we can temporally follow the cooling of hot carriers through changes in mobility. A link can be established between charge carrier cooling and the emergence of phonon-carrier interactions, possibly through the formation of a polaron.[5] However, the latter cannot be directly observed as a change of mobility when cold carriers are directly formed. We compare these results across different perovskite compositions to elucidate the role of cations and anions.

16:45 - 17:00
Sanchez, Sandy
University of Fribourg
Flash infrared annealing method: the pulse time to control the perovskite crystal nucleation and growth from solution
Sandy Sanchez
University of Fribourg
Sandy Sanchez a
a, Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, Lausanne, CH

This works unveils how to produce defect-free and compact perovskite films by using the Flash Infrared Annealing (FIRA) method, describing the kinetic processes involved. It addresses how FIRA induces crystallization in perovskite films.1, 2 This includes the nucleation of crystals followed by their growth and the kinetics of the crystal growth from solution as a function of the pulsed time. FIRA is a cost-effective fast synthesis process, which provides control over the final morphology of the perovskite thin film. The FIRA setup has been employed to synthesize highly crystalline organic-inorganic perovskite films and transparent inorganic conductive layers, and adding it to the manufacturing process helps to overcome the perovskite stability challenge.

To make FIRA effective is necessary to understand the physicochemical phenomena that take place during the crystallization of the synthesized film. Is important, for example, to know the pathways of the nucleation and crystal growth through intermediate phases. In FIRA the crystallization occurs by it intermediate phases until the final crystal phase as it happens on the antisolvent method and posterior thermal low temperature annealing. The difference consists in the fastness on the process, which in FIRA is on the order of milliseconds and in AS is on the order of seconds.  As the solvent evaporates, the chemical potential of the solution changes, eventually reaching supersaturation, allowing the formation of a new phase by crystal growth.  Once the supersaturation is reached nucleation clusters appear, followed by the growth these crystals.


17:00 - 17:15
Ahlawat, Paramvir
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
Atomistic Simulations of Nucleation of Lead Halide Perovskites
Paramvir Ahlawat
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH

I am a PhD student at EPFL. I am working on atomistic simulations of nucleation and crystal growth of lead halide perovskites.

Paramvir Ahlawat a, Michele Parrinello b, Ursula Rothlisberger a
a, Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, Lausanne, CH
b, Swiss Federal Institute of Technology (ETH) Zurich, CH

Control over morphology plays a very important role in obtaining high efficiencies of lead halide perovskites solar cells. Nucleation and crystal growth processes dictate the evolution of morphology. To probe the atomic level mechanism of nucleation, experimental methods are limited by the length and time scales. Therefore, we perform the molecular dynamics (MD) simulations of homogeneous and heterogeneous nucleation of lead halide perovskites. However, nucleation from solution is a typical example of a rare event process and therefore it poses a very big challenge to perform the MD simulations. Here, we use the enhanced sampling technique of Metadynamics to overcome these challenges. Metadynamics employs a bias potential which is constructed from a few collective coordinates of the system. In this study, we introduce new generalized reaction coordinates to form perovskite crystals from MD simulations. From our simulations[1], we layout the individual stages of the nucleation of lead halide perovksites. We find that the monovalent cations plays a very important role to initiate the nucleation process. We also identify the relevant intermediate metastable structures formed during nucleation. Our simulations of nucleation of mixed-cation systems reveal the in-depth details of the effects of different cations on the evolution of morphology.

17:15 - 17:30
Schutt, Kelly
Department of Physics of University of Oxford
Overcoming Zinc Oxide Interface Instability with Methylammonium-free Perovskites for High Performance Solar Cells
Kelly Schutt
Department of Physics of University of Oxford, GB
Kelly Schutt a, Pabitra Nayak a, Alexandra Ramadan a, Bernard Wenger a, Yen-Hung Lin a, Henry Snaith a
a, University of Oxford, GB

Perovskite solar cells have achieved the highest power conversion efficencies on metal oxide n-type layers, including SnO2 and TiO2. Despite ZnO having superior optoelectronic properties to these two metal oxides, such as improved transmittance, higher conductivity, and closer conduction band alignment to methylammonium (MA)PbI3, ZnO has largely been overlooked due to a chemical instability with the architypical MAPbI3, which leads to the rapid decomposition of the perovskite. While surface passivation techniques have somewhat mitigated this instability, investigations as to whether alternative metal halide perovskites also exhibit this instability with ZnO are yet to be undertaken. We develop experimental methods to elucidate the degradation mechanisms in ZnO-MAPbI3 interfaces. By substituting MA with formamidinium (FA) and cesium (Cs), we greatly enhance the stability of the perovskite-ZnO interface and find that stability compares favorably with SnO2-based devices after high intensity UV irradiation and 85°C thermal stressing. Devices comprising FA/Cs cations on ZnO reach 21.1% scanned power conversion efficiency and 18% steady-state power output, comparable to devices on SnO2. Our work demonstrates that, provided we move away from MA containing perovskites, ZnO is an equally feasible n-type charge extraction layer as SnO2 for use in perovskite solar cells, with many additional advantages.

Session C3
Chair: Claudia Barolo
14:30 - 14:45
Kubicki, Dominik
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
Cadmium Doping: Incorporation and Phase Segregation in Mixed-Cation and Mixed-Halide Lead Perovskites from Solid-State NMR
Dominik Kubicki
Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, CH
Dominik Kubicki a, Daniel Prochowicz a, b, Albert Hofstetter a, Shaik Zakeeruddin a, Michael Grätzel a, Lyndon Emsley a
a, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, Lausanne, CH
b, Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland

Cadmium doping has recently emerged as a strategy for supressing atomic vacancies and improving stability of perovskite solar cells (PSCs), as well as a means of postsynthetic tailoring of perovskite nanocrystals.[1-3] While the beneficial effects of cadmium doping are evident, the atomic-level microstructure of cadmium inside the doped perovskites remains unclear. We have recently shown that solid-state NMR is perfectly suited for probing dopant incorporation and phase heterogeneity in complex perovskite materials since it directly reveals the local atomic environment of the dopant.[4-6]

Here, using 113Cd MAS NMR at 21.1 T we provide for the first time atomic-level characterization of the cadmium-containing phases that are formed upon cadmium doping of multi-cation and multi-anion lead-halide perovskites. Contrary to current belief, cadmium is not incorporated into organic-inorganic lead halide perovskites and forms secondary non-perovskite phases instead. We also find that, consistent with current understanding, cadmium is incorporated into the all-inorganic CsPbBr3 perovskite.

Figure: Schematic representation of the previously suggested scenario for cadmium incorporation into the perovskite lattice: (a) parent APbI3 lattice (A=MA, FA, Cs+), (b) B-site replacement.

14:45 - 15:00
Macpherson, Stuart
University of Cambridge - UK
Modulating Nanoscale Defect States in Halide Perovskite Films
Stuart Macpherson
University of Cambridge - UK, GB
Stuart Macpherson a, Andrew Winchester b, Elizabeth Tennyson a, Krzystof Galkowski a, Tiarnan Doherty a, Miguel Anaya a, Christopher Petoukhoff b, Michael Man b, Keshav Dani b, Samuel Stranks a
a, Cavendish Laboratory, Department of Physics, University of Cambridge, UK, JJ Thomson Avenue, Cambridge, GB
b, Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, Japan 904-0495

The photovoltaic performance of world-leading organic-inorganic halide perovskite (OHP) solar cells remains limited by defective electronic states, which introduce non-radiative recombination pathways for charge carriers. In OHP thin films, it is emerging that nanoscale surface defects are the most prevalent and thus have greatest impact on luminescence and device efficiency [1-3].

We employ a state-of-the-art photoemission electron microscopy (PEEM [4,5]) setup to map local surface defect states on triple cation, mixed-halide perovskite ((CsFAMA)Pb(I0.83Br0.17)3) films with 30 nm spatial resolution. We detect a nanoscale population of defective grains which exhibit significant photoemission from intraband trap states. Integrating PEEM with time-resolved pump-probe spectroscopy enables us to monitor the rate and intensity of hole trapping into these defect sites. Confocal photoluminescence maps show a clear anti-correlation between areas of high photoluminescence intensity and the locations of defect-rich grains. We have previously shown the incorporation of potassium halides [6] or light and atmospheric treatments [7] can substantially increase luminescence yields of perovskite films, thereby reducing trap densities.

In this work we utilise light treatments in a variety of atmospheric conditions as a lever to control surface trap distribution. With PEEM, we observe the creation of nanoscale defect states during in situ illumination of the perovskite, in ultra-high vacuum conditions. Conversely, illumination in an oxygen-rich environment leads to a tuneable suppression of the photoemission from defect-rich sites. We show that the photoluminescence heterogeneity previously reported for perovskite films is inherently linked to the distribution of these nanoscale defects and can be similarly controlled.

Finally, we apply Kelvin probe force microscopy (KPFM) to elucidate the nature of defect-rich grains and reveal nanoscale variation in work function, namely local n-type regions which retain a prominent intraband density of states.

This work establishes a clear understanding of what factors impact defects on multiple time and length scales, providing guidelines for improved passivation and ultimately device performance.

15:00 - 15:30
Bach, Udo
Monash University / CSIRO
Towards Single-Crystalline Perovskite Devices
Udo Bach
Monash University / CSIRO

Udo Bach is a full professor at Monash University in the Department of Chemical Engineering; the Deputy Director of the ARC Centre of Excellence in Exciton Science and an ANFF-VIC Technology Fellow at the Melbourne Centre of Nanofabrication (MCN).  He received his PhD from the Swiss Federal Institute of Technology (EPFL, Switzerland) working in the research group of Prof Michael Grätzel and worked for 3 years in a technology start-up company in Dublin (Ireland).  Subsequently he spent 15 months as a postdoc in the group of Prof. Paul Alivisatos in UC Berkeley (USA) before moving to Monash University in November 2005 to establish his own research group.


Prof Bach has a strong background in the area of photovoltaics and nanofabrication.  He is involved in fundamental and applied research in the area of perovskite and dye-sensitized solar cells.  He has additional research activities in the area of nanofabrication, DNA-directed self-assembly, nanoprinting, plasmonics for sensing, photovoltaic applications and combinatorial photovoltaic materials discovery.

Udo Bach a, Wenxin Mao a
a, ARC Centre of Excellence in Exciton Science, Department of Chemical Engineering, Monash University, Clayton, VIC, Australia

Solution-processed thin films of lead halide perovskites show exceptional optoelectronic properties, making them interesting candidates for a range of applications such as solar cells and light-emitting diodes. The thickness and crystallite-size in these films is typically in the sub-micron range, resulting in an abundance of grain-boundaries. Here we will describe techniques for growing thin single-crystalline lead perovskite crystallites with edge lengths of several tens of microns and thicknesses of around 1 micron, starting from single-source 1D lead halide perovskite precursors. We report our recent work of fabricating active electro-optical modulators (AEOM) from these crystals using focused-ion beam milling. These AEOMs exhibit > 98% light transmission intensity modulation with an applied external voltage of 45 V. In the final section of this talk we will report our recent efforts of growing single-crystalline mixed-halide lead perovskite platelets and demonstrate the visualization of photoinduced phase segregation in these materials.1 Upon illumination we observe the formation of iodide-rich domains throughout the entire crystal, demonstrating that light-induced phase segregation also occurs efficiently in absence of grain boundaries. Narrowband fluorescence imaging and time-resolved spectroscopy provided new insight into the nature of phase segregated domains and the collective impact on optoelectronic properties.

15:30 - 15:45
Uller Rothmann, Mathias
University of Oxford, GB
Reliable Atomic-Resolution Observations of the Nanoscopic Properties of Hybrid Perovskite Thin Films
Mathias Uller Rothmann
University of Oxford, GB
Mathias Uller Rothmann a, Judy Kim b, c, d, Juliane Borchert a, Kilian Lohmann a, Colum O'Leary b, Alex Sheader b, Michael Johnston a, Henry Snaith a, Peter Nellist b, Laura Herz a
a, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, GB
b, Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH
c, ePSIC, Diamond Light Source
d, Rosalind Franklin Institute

Atomic resolution transmission electron microscope (TEM) studies have been invaluable in understanding the most fundamental properties of many crystalline semiconductor solar cell materials. The large electron energies involved in most TEM studies have, however, meant that studying the typically unstable photoactive hybrid perovskites reliably has been challenging.[1] Particularly the very close structural relationship between certain crystallographic orientations of the pristine perovskite structure and lead iodide has led to previous atomic resolution studies generating ambiguous result that do not correspond well to the crystallographic properties observed with other methods.[2] Using extremely low dose scanning TEM (STEM), we have been able to image hybrid perovskites, including MAPbI3 and FAPbI3, with atomic resolution in accordance to the generally agreed upon crystal structures. As a result, we have been able unequivocally to distinguish the different components of the perovskite structure within the crystal lattice. Furthermore, we have identified nanoscopic domains of PbI2 integrating seamlessly within the perovskite lattice, suggesting that the benign nature of the presence of some PbI2 can be due to the continuous nature of the crystal lattice. These findings pave the way for a significant shift in the level of detail with which the microscopic properties of hybrid photoactive perovskite can be studied, including the crystallographic nature of grain boundaries and the distribution of dopants.

15:45 - 16:00
Samu, Gergely
University of Szeged
Modulation of Excited State Dynamics in Lead Halide Perovskite Films with Electrical Bias
Gergely Samu
University of Szeged, HU
Gergely Samu a, b, c, R.A. Scheidt c, d, A. Balog a, C. Janáky a, b, P.V. Kamat c, d
a, Department of Physical Chemistry and Materials Science, Interdisciplinary Excellence Centre, University of Szeged, Rerrich Square 1, Szeged, HU
b, ELI-ALPS Research Institute, Szeged, Dugonics sq. 13, 6720, Hungary
c, University of Notre Dame, Notre Dame, Indiana 46556, EE. UU., Notre Dame, US
d, University of Notre Dame, Notre Dame, Indiana 46556, EE. UU., Notre Dame, US

In recent years the emergence of hybrid organic-inorganic lead halide perovskites revitalized several semiconductor related research fields. This growing interest is mainly caused by the rapid efficiency increase of derived solar cells, which reached 22.3% in the past 10 years. To unravel the reasons behind their outstanding performance, it is important to understand their optoelectronic properties, especially their excited state dynamics under operating conditions.

Spectroelectrochemical methods are viable tools to determine fundamental optoelectronic properties (band edge and trap state energies) and electrochemical bias induced chemical changes in these materials.1 However, to probe charge carrier dynamics, it is essential to utilize ultrafast laser techniques, as the related processes fall into the femto- or picosecond timescale.

In my presentation the effect of applied bias on the charge carrier dynamics of perovskite electrodes will be discussed. Ultrafast spectroelectrochemical experiments were carried out on FTO/TiO2/CsPbBr3 system by coupling ultrafast transient absorption spectroscopy with electrochemical techniques.2 It was found that the excitonic feature of CsPbBr3 is responsive to the applied external bias, within the materials electrochemical stability window. The accumulation of electrons on the TiO2/CsPbBr3 interface had a pronounced effect on charge carrier lifetimes in CsPbBr3. This change in charge carrier lifetimes was completely reversible, showing the dependence of excited state dynamics on the externally controlled charge carrier density. This validates the in situ electrochemical transient absorption measurement as a useful tool to probe the charge carrier injection process in different semiconductor systems.

Samu, G. F., Scheidt, R. A., Kamat, P. V. & Janáky, C. Electrochemistry and Spectroelectrochemistry of Lead Halide Perovskite Films: Materials Science Aspects and Boundary Conditions. Chem. Mater. 30, (2018).

Scheidt, R. A., Samu, G. F., Janáky, C. & Kamat, P. V. Modulation of Charge Recombination in CsPbBr3 Perovskite Films with Electrochemical Bias. J. Am. Chem. Soc. 140, 86–89 (2018).

16:00 - 16:30
Coffee Break
16:30 - 17:00
Malinkiewicz, Olga
Saule Technologies
Step by Step toward Commercially Available Flexible Perovskite Modules
Olga Malinkiewicz
Saule Technologies, PL
Tanja Ivanovska a
a, Saule Technologies, Mokotowska 1, Warsaw, 00-640, Warszawa, PL

The perovskite solar cell technology has undoubtedly taken the solar cell research community by storm. The overwhelming performance of the perovskite based solar cells, regardless of the device architecture or the specific elemental composition of the organo-metal-halide perovskite absorbers, sparked a natural drive to start looking forward to upscaling and commercialization of this technology despite of its “youth”.

It might come as no surprise that the transition from laboratory to industry has proven challenging. Many issues must be re-developed in order to meet industrialization; among them large area deposition techniques, safety standards and material wastage without compromising efficiency and stability. Thus, a cost-effective, reliable fabrication process capable of delivering highly efficient, large-area perovskite modules is yet to be demonstrated.

Saule technologies has been developing a fully scalable inkjet printing process of perovskite solar cells and modules on flexible substrates. This talk will focus on recent advancements in the technology and the product development process required to bring inkjet printed perovskite modules closer to the commercial use. Moreover, it will underline the unique properties of the inkjet printing technique, the ink formulations and specific post-processing treatments which allow scalable solution-based fabrication of high-quality perovskite films and devices, processed in ambient atmosphere.

17:00 - 17:15
McMeekin, David
ARC Centre of Excellence in Exciton Science, Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
Solution-Processed All-Perovskite Multi-Junction Solar Cells
David McMeekin
ARC Centre of Excellence in Exciton Science, Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
David McMeekin a, b, Suhas Mahesh a, Nakita Noel a, Matthew Klug a, JongChul Lim a, Jonathan Warby a, James Ball a, Laura Herz a, Michael Johnston a, Henry Snaith a
a, Clarendon Laboratory, Department of Physics, Oxford University, Oxford OX1 3PU, UK
b, ARC Centre of Excellence in Exciton Science, Department of Chemical Engineering, Monash University, Clayton, VIC, Australia

Multi-junction device architectures can increase the power conversion efficiency (PCE) of photovoltaic (PV) cells beyond the single-junction thermodynamic limit. However, these devices are challenging to produce by solution-based methods, where dissolution of underlying layers is problematic. By employing a highly volatile acetonitrile(CH3CN)/methylamine(CH3NH2) (ACN/MA) solvent-based perovskite solution, we demonstrate fully solution-processed absorber, transport and recombination layers for monolithic all-perovskite tandem and triple-junction solar cells. By combining FA0.83Cs0.17Pb(Br0.7I0.3)3 (1.94 eV) and MAPbI3 (1.57 eV) junctions, we reach two-terminal tandem PCEs of over 15 % (steady-state). We show that a MAPb0.75Sn0.25I3 (1.34 eV) narrow band gap perovskite can be processed via the ACN/MA solvent-based system, demonstrating the first, proof-of-concept, monolithic all-perovskite triple-junction solar cell with an open-circuit voltage reaching 2.83 V. Through optical and electronic modeling, we estimate the achievable PCE of a state-of-the-art triple-junction device architecture to be 26.7%. Our work opens new possibilities for large-scale, low-cost, printable perovskite multi-junction solar cells.

17:15 - 17:30
Burgess, Claire
Department of Applied Physics, Eindhoven University of Technology, NL-5600 MB Eindhoven, The Netherlands
Interface Studies of Metal Oxides Grown Directly on Hybrid Perovskite by Atomic Layer Deposition
Claire Burgess
Department of Applied Physics, Eindhoven University of Technology, NL-5600 MB Eindhoven, The Netherlands
Claire Burgess a, Farzad Mardekatani Asl a, Valerio Zardetto b, Herbert Lifka b, Sjoerd Veenstra b, Mariadriana Creatore a
a, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
b, TNO - Solliance, High Tech Campus 21, 5656 AE, Eindhoven, The Netherlands

In the field of perovskite solar cells, atomic layer deposition (ALD) is an increasingly important tool for the deposition of metal oxides on top of perovskite. The chemical reactions of the ALD precursors with a surface allow low temperature growth of layers with unsurpassed uniformity. Moreover, the process is facile to scale, offering the choice of deposition under vacuum (conventional) or at atmospheric pressure (spatial ALD).[1] The potential value of adopting ALD for layer growth directly on perovskite was earlier established with the application of an ultrathin Al2O3 layer on methylammonium lead iodide.[2] We have recently further corroborated this by deposition of Al2O3 on wide bandgap, mixed cation, mixed halide perovskite, boosting the Voc of cells by over 100mV.[3] Next to the case study of Al2O3, several other ALD metal oxides have been successfully implemented in perovskite solar cells, among which is SnO2. It is well known that the latter, grown on perovskite with an organic interlayer between,[4] operates as both an effective electron transport layer (ETL) and as a barrier to the diffusion of chemical species through the cell. However, when ALD SnO2 is grown directly on top of perovskite, the solar cell performance is worse, although this can be mitigated to a certain degree by adjustment of the perovskite composition.[5]

In this contribution, we therefore select Al2O3 and SnO2 and report on an in-depth study of their growth behavior on (Cs,FA)Pb(I,Br)3 perovskite, with the purpose of providing insight on the chemical changes at the perovskite/metal oxide interface, responsible for poor cell performance with SnO2 but surface passivation with Al2O3.

ALD allows controlled monolayer by monolayer growth on a substrate, so through x-ray photoelectron spectroscopy, including angle resolved measurements, it is possible to study the changing composition at the perovskite interface as metal oxide is grown.[6] Exposure of the (Cs,FA)Pb(I,Br)3 perovskite to water (the shared oxygen source in our ALD processes) at a substrate temperature of less than 100° C, does not significantly affect the surface composition of the perovskite.  Instead, the precursor used as the metal source is found to be of greater consequence. For SnO2 growth (using tetrakis(dimethylamino)tin), we prove that the bulk of the (Cs,FA)Pb(I,Br)3 perovskite is unchanged compared to pristine perovskite, but at the interface between the two materials a layer consisting of some perovskite constituents (namely Pb, Br and decomposed FA) is gradually formed. Upon deposition of a layer of thickness representative of an ETL (> 10nm SnO2), it is found that the interface layer (after exposure using a peel-off technique) consists of approximately 10% decomposed FA, 70% Pb and 20% Br, and is < 1nm thick. For the growth of Al2O3 on (Cs,FA)Pb(I,Br)3 using trimethylaluminum precursor, this interface developed is thinner. To determine the factors affecting the formation of interfaces we vary deposition parameters and also compare metal sources, for example slower Al2O3 nucleation is observed with dimethylaluminum isopropoxide than trimethylaluminum precursor. The comparison of the interfaces of SnO2 and Al2O3 with perovskite, along with other contributing factors such as the band alignment, the inherently different thickness of metal oxide and cell configurations (p-i-n vs. n-i-p) employed are discussed with reference to the differing cell performance.

Hooman Mehdizadeh Rad, Jai Singh
Study of Diffusion Length of Charge Carriers in Perovskite Solar Cells
Loreta Angela Muscarella, Sandy Sanchez, Andries Lof, Michael Saliba, Bruno Ehrler
Impact of Flash Infrared Annealing on Growth and Photophysics of MAPbI3 Perovskite
Loreta Angela Muscarella, Eline M. Hutter, Jan Versluis, Huib Bakker, Bruno Ehrler
Carrier cooling in Perovskite under Hydrostatic Pressure Probed by Transient Absorption Spectroscopy
BongSoo Kim
Structure-to-photovoltaic property relationships in rhodanine-based small molecule acceptors
Jovana Milic, Dominik Kubicki, Dongqin Bi, Xiong Li, Lyndon Emsley, Michael Graetzel
Multifunctional Molecular Modulation for Stable and Efficient Hybrid Perovskite Solar Cells
Silvia Motti, Timothy Crothers, Rong Yang, Jianpu Wang, Laura Herz
Energy Cascades in Mixed-Phase Perovskite Thin Films: Charge-Carrier Dynamics and Mobilities
Dengyang Guo, Valentina Caselli, Eline Hutter, Tom Savenije
Predicting the Maximum Open Circuit Voltage of Perovskite Solar Cells from Time-Resolved Measurements
Lucie McGovern, Loreta Muscarella, Moritz Futscher, Bruno Ehrler
Quantification of Ion Migration in MAPbBr3 Solar Cells with varying Grain Size
Nick Vlachopoulos, Anders Hagfeldt, Michael Grätzel
Electrochemical Methods in Dye-Sensitized and Perovskite Solar Cell Research
Cheng-Hung Hou, Jing-Jong Shyue, Shu-Han Hung, Li-Ji Jhang
Artifact-Free Depth Profiles Acquired by ToF-SIMS and Their Utility in Revealing Perovskite Solar Cells' Natures
Andrea Rubino, Mauricio Calvo, Juan Galisteo, Hernán Míguez
APbX3 Perovskite Nanocrystals in Porous Matrices: Size Control and New Potential Applications
Ajay Singh, Alessio Gagliardi
Drift-diffusion and Machine Learning for High Efficiency Perovskite-Perovskite based Tandem Solar Cells
Regioregular Terpolymers for High-Performance Organic Photovoltaic Devices
Sameh Hamzawy, Pawel Wagner, Attila Mozer, Andrew Nattestad
Redox Mediators Effect on The Up-Convesion System Performance for Intermediate Band Dye Solar Cells Applications
Isabella Poli, Ulrich Hintermair, Miriam Regue, Santosh Kumar, Emma Sackville, Jenny Baker, Trystan Watson, Salvador Eslava, Petra Cameron
Inexpensive Metal Free Encapsulation Layers Enable Halide Perovskite Based Photoanodes for Water Splitting
Seyedali Emami, Dzmitry Ivanou, Adélio Mendes
Leonardo Buizza, Zhiping Wang, Timothy Crothers, Rebecca Milot, Henry Snaith, Michael Johnston, Laura Herz
Charge-Carrier Dynamics, Mobilities and Diffusion Lengths of 2D-3D Lead Halide Perovskites
Hsin-Hsiang Huang, Leeyih Wang, King-Fu Lin
High-Performance and Robust CH3NH3PbI3/Nanoclay Hybrid Perovskite Solar Cells Under High-Humidity Condition
Karen Valadez-Villalobos, Alejandra Castro-Chong, Gerko Oskam, Tom Aernouts, Juan A. Anta
Effect of the Electron Selective Contact Material on the performance and Stability of Hybrid Perovskite Solar Cells
Chuantian Zuo, Andrew D. Scully, Doojin Vak, Wenliang Tan, Xuechen Jiao, Christopher R. McNeill, Dechan Angmo, Liming Ding, Mei Gao
Self-Assembled Two-Dimensional Perovskites Layers for Efficient Printable Solar Cells
O-Pil Kwon, Su-Kyo Jung, Jong-Bum Lee, Dae Woon Lee, Mojca Jazbinsek, Jong H. Kim
Organic Electron Transporting Materials with Naphthalene Diimide Semiconducting Core and Their THz Spectroscopy
Diego Di Girolamo, Aldo Di Carlo, Danilo Dini, Antonio Abate
Recombination and Electrical Stability. What Happens at the HSL/Perovskite Interface and How to Solve it
Meiqian Tai, Xingyue Zhao, Hong Lin
Flash-evaporation Printing Methodology for Perovskite Thin Films and Efficient Solar Cells
Cristina Teixeira, Luísa Andrade, Adélio Mendes
Preparation of carbon-based electrodes to be used as back-contact in perovskite solar cells
Jay Patel, Qianqian Lin, Olga Zadvorna, Christopher Davies, Laura Herz, Michael Johnston
Utilizing Temperature-Dependent Photocurrent Spectroscopy to Extract the Exciton Binding Energy of CH3NH3PbI3 Perovskite Thin-Films
Eike Köhnen, Marko Jošt, Anna Belen Morales-Vilches, Philipp Tockhorn, Amran Al-Ashouri, Bart Macco, Lukas Kegelmann, Lars Korte, Bernd Stannowski, Bernd Rech, Rutger Schlatmann, Steve Albrecht
Highly Efficient Monolithic Perovskite Silicon Tandem Solar Cells: Analysing Current-Mismatch Conditions
Askhat Jumabekov, Giovanni DeLuca, Yinghong Hu, Gede Adhyaksa
Transparent Quasi-Interdigitated Electrodes for Semitransparent Perovskite Back-Contact Solar Cells
Ludmila Cojocaru, Karl Wienands, Matthias Breitwieser, Alexander J. Bett, Patricia S. C. Schulze, Jan Christoph Goldschmidt, Stefan W. Glunz
Evaporation-based techniques for high quality absorbers (Pb and Pb-free) prepared on structured substrates
Isabel Mesquita, Luísa Andrade, Adélio Mendes
Impact of Environmental Conditions in Perovskite Solar Cells: Relative Humidity and Oxygen
Blaise Godefroid, Gregory Kozyreff
Optimisation of Metallic Interconnecting Layer in Homo-Tandem Cells
Giuliana Giuliano, Sebastiano Cataldo, Michelangelo Scopelliti, Tiziana Fiore, Bruno Pignataro
Multilayer Copper-Rich Transparent Electrode as an Alternative Top Anode for High-Performance Semitransparent Perovskite Solar Cells
Chi-Yuan Chang, Leeyih Wang, Yang-Fang Chen, Fang-Chi Hsu
Perovskite Solar Cells Based on Self-assembled Hole-Extraction Monolayer with Conjugated Polyelectrolyte
Wolfgang Köntges, Pavlo Perkhun, Rasmus R. Schröder, Riva Alkarsifi, Olivier Margeat, Christine Videlot-Ackermann, Jörg Ackermann, Martin Pfannmöller
Real-Space Correlation of Crystallinity and Material Phase Distribution in Non-Fullerene Acceptor Blends
Rúben Madureira, Jorge Martins, Seyedali Emami, Joaquim Mendes, Adélio Mendes
Hermetic Sealing of Perovskite Solar Cells at Process Temperature Lower than 85 °C
Emanuele Smecca, Ajay Jena, Ioannis Deretzis, Gyu Min Kim, Yohuei Numata, Silvia Scalese, Giovanni Mannino, Corrado Bongiorno, Antonino La Magna, Tsutomu Miyasaka, Alessandra Alberti
Fully solvent-free preparation of MAPbI3 films for photovoltaic application
Natalie Mica, Stuart Thomson, Ifor Samuel
Mobility of Non-fullerene Acceptors Using a Time of Flight Method
Lukas Kegelmann, Philipp Tockhorn, Max Grischek, José A. Márquez, Thomas Unold, Wilfried Lövenich, Dieter Neher, Steve Albrecht
SpiDOT: mixtures of undoped Spiro-OMeTAD and PEDOT to reduce charge recombination and absorption losses in monolithic perovskite/silicon tandem solar cells
Yuriy Karpov, Danila Saranin, Lev Luchnikov, Vsevolod Mazov, Inga Ermanova, Pavel Gostischev, Sergey Didenko, Denis Kuznetsov, Aldo Di Carlo
High-performing, hysteresis-free perovskite solar cells with inverted structure for indoor application
Jhon Puerres-Puerres, Pablo Ortiz-Herrera, María T. Cortés M.
Photoelectrochemical Hydrogen Production Using Thin Films of Polypyrrole Electrochemically Synthesized
Pavao Andričević, Pavel Frajtag, Vincent Pierre Lamirand, Andreas Pautz, Márton Kollár, Bálint Náfrádi, Andrzej Sienkiewicz, Tonko Garma, László Forró, Endre Horváth
100 Hours Operation of Large Perovskite Single Crystals for Gamma Dose-rate Measurements
Pavlo Perkhun, Elena Barulina, Sadok Ben Dkhil, Pascal Pierron, Wolfgang Köntges, Martin Pfannmöller, Christine Videlot-Ackermann, Olivier Margeat, Jean-Jacques Simon, Jörg Ackermann
Digital printing of polymer solar cells based on non-fullerene acceptors: from spin coating to digital printing
Fabian Schackmar, Helge Eggers, Tobias Abzieher, Gerardo Hernandez-Sosa, Bryce S. Richards, Uli Lemmer, Ulrich W. Paetzold
Inkjet-Printed Micron-Thick Triple-Cation Absorber Layers with Columnar Crystals in Perovskite Solar Cells Exceeding 18% Stabilized Power Conversion Efficiency
Dmitry Baranov, Stefano Toso, Liberato Manna
Cesium Lead Bromide Nanocrystal Superlattices: from Optical Properties to Applications
Naveen Venkatesan, John Labram, Rhys Kennard, Ryan DeCrescent, Hidenori Nakayama, Clayton Dahlman, Erin Perry, Jon Schuller, Michael Chabinyc
Charge Carrier Dynamics and Structural Defects in Layered Hybrid Perovskites
Nga Phung, Aboma Merdasa, Antonio Abate
Real-time observation of ion migration interaction with grain boundaries in methylammonium lead iodide by photoluminescence imaging
Diego De Girolamo, Ibrahim M. Dar, Danilo Dini, Lorenzo Gontrani, Ruggero Caminiti, Alessandro Mattoni, Michael Graetzel, Simone Meloni
Dual Effect of Positive and detrimental effects of humidity on cesium lead bromide
Davide Moia, Ilario Gelmetti, Phil Calado, William Fisher, Michael Stringer, Onkar Game, Yinghong Hu, Pablo Docampo, David Lidzey, Emilio Palomares, Joachim Maier, Jenny Nelson, Piers Barnes
The device physics of metal halide perovskite interfaces, part 2: equivalent circuit model
Simon Ternes, Tobias Börnhorst, Jonas A. Schwenzer, Ihteaz M. Hossain, Waldemar Mehlmann, Philip Scharfer, Wilhelm Schabel, Uli Lemmer, Bryce S. Richards, Ulrich W. Paetzold
In-situ analysis of the drying process in blade-coated perovskite absorber layers for efficient solar cells
David O. Tiede, Juan F. Galisteo-López, Maurico E. Calvo, Hernán Míguez
Improving the Bulk Emission Properties of CH3NH3PbBr3 by Modifying the Halide-Related Defect Structure
Gregor Trimmel, Thomas Rath, Stefan Weber, Jasmin Handl, Theodoros Dimopoulos, Birgit Kunert
Investigation of Triple Cation Tin Perovskite Solar Cells
TAUHEED MOHAMMAD, Viresh Dutta, Mahesh Kumar, Suresh Chand
Spray Deposition Technique for Utilizing Förster Energy Transfer in Bulk Heterojunction Organic Solar Cells: Role of Applied Voltage
Tetsuhiko Miyadera, Yuto Auchi, Kohei Yamamoto, Noboru Ohashi, Tomoyuki Koganezawa, Yuji Yoshida, Masayuki Chikamatsu
Real-Time Crystallization Analysis of Organolead-Halide Perovskite
Christof Schultz, Andreas Bartelt, Antje Neubauer, Cornelia Junghans, Marko Jost, Lukas Kegelmann, Rutger Schlatmann, Steve Albrecht, Bert Stegemann
Time-resolved photoluminescence imaging reveals material modifications of laser scribes in perovskite solar cells
Stefania Cacovich, Adrien Bercegol, Daniel Ory, Daniel Suchet, Olivier Fournier, Jean-François Guillemoles, Jean Rousset, Laurent Lombez
Quantitative Assessment of Photonic and Electronic Properties in Multi-Cation Halide Perovskites through Multi-Dimensional Luminescence Imaging
Richard Ciesielski, Alexander Biewald, Frank Schäfer, Pablo Docampo, Achim Hartschuh
Temperature Dependent Charge Carrier Diffusion and the Role of Grain Boundaries in Thin Film Perovskites
Artiom Magomedov, Amran Al-Ashouri, Ernestas Kasparavicius, Gediminas Niaura, Tadas Malinauskas, Steve Albrecht, Vytautas Getautis
Hole-Selective Monolayers: Synthesis, Deposition, and Application in Efficient Perovskite Solar Cells.
Ahmed Said, Qichun Zhang, Dada Shaikh, Sidhanath Bhosale, Yang Wang, Tsuyoshi Michinobu
Organic Non-Fullerene Acceptors as Efficient Electron Transporting Materials in Inverted Perovskite Solar Cells
Ula Yasin, Lukas Kegelmann, Felix Kraffert, Steve Albrecht, Jan Behrends
Quantitative EPR Analysis of Doped Spiro-OMeTAD
Damiano Ricciarelli, Daniele Meggiolaro, Filippo De Angelis
Computational Modelling of Defect Chemistry of Tin Halide Perovskites for Solar Cells Applications
Giulia Lucarelli, Sergio Castro-Hermosa, Michiel Top, Matthias Fahland, John Falteich, Thomas M. Brown
Ultra-Thin Flexible Glass Perovskite Solar Cells as Outstanding Photovoltaic Light Harvesters Under Indoor Illumination
Paolo Mariani, Babak Taheri, Maryam Esmaeilzadeh, Sara Pescetelli, Antonio Agresti, Aldo Di Carlo
Automatized Low Temperature Deposition of Blocking TiO2 Layer for Large Area Perovskite Solar Devices
Amran Al-Ashouri, Artiom Magomedov, Marcel Roß, Marko Jošt, Ganna Chistiakova, Eike Köhnen, Sergiu Levcenco, José A. Márquez Prieto, Tadas Malinauskas, Charles J. Hages, Thomas Unold, Lars Korte, Bernd Rech, Vytautas Getautis, Steve Albrecht
Universal Self-Assembled Monolayer Contacts for >20% Efficient Perovskite Solar Cells
Maning Liu, Zhifeng Deng, Haichang Zhang, Paola Vivo
Dopant-free Hole-transporting Materials Via Thionation Approach Towards Stable and Efficient Perovskite Solar Cells
Eros Radicchi, Edoardo Mosconi, Fausto Elisei, Francesca Nunzi, Filippo De Angelis
Understanding the Solution Chemistry of Lead Halide Perovskite Precursors
Eider A. Erazo Erazo, Daniel Castillo-Bendeck, Pablo Ortiz, María T. Cortés
Electrodeposited PEDOT:DS-ClO4 as a Promising Hole Transporting Material
Babak Taheri, Giorgio Cardone, Aldo Di Carlo, Francesca Brunetti
Automated Scalable Spray Coating of SnO2 Colgel and SnO2 Nano Particles for the Realization of Low Temperature and Large Area Perovskite Solar Cells
Zahra Andaji-Garmaroudi, Mojtaba Abdi-Jalebi, Stuart Macpherson, Alan Bowman, Richard H. Friend, Samuel D. Stranks
Highly Stable Light Emitting Diodes via Potassium Passivation
Enzo Menna, Teresa Gatti
Chemical Modification of Carbon Nano Structures Leading to Hybrid Materials for Photovoltaics
Alessandro Senocrate, Igor Moudrakovski, Joachim Maier
Short-Range Methylammonium Dynamics in Methylammonium Lead Iodide
Dewalque Jennifer, Daem Nathan, Spronck Gilles, Schrijnemakers Audrey, Maho Anthony, Colson Pierre, Lobet Michael, Piron Pierre, Loicq Jérôme, Henrist Catherine, Cloots Rudi
Opal-like CH3NH3PbI3 perovskite solar cells : effect of the 3D structuration on the conversion efficiency
Yun Li, Wallace Woon-Fong Leung
Performance enhancement of perovskite solar cell with graphene nanofibers
Anna Pachariyangkun, Taweesak Sudyoadsuk, Vinich Promarak
Naphthothiadiazole Core Flanked with Furan and Thiophene as Small Molecule Donor for High Performance Solution-processed Bulk Heterojunction Solar Cells
Xingdong Ding, Cheng Chen, Ming Cheng
Highly Efficient Phenothiazine 5, 5-Dioxide-Based Hole Transport Materials for Planar Perovskite Solar Cells with PCE Exceeding 20%
Shigehiko Mori, Haruhi Ohka, Hideyuki Nakao, Akio Amano, Kenji Todori
Large Size (703 cm2) and Film Based Perovskite Photovoltaic Module Development with Inverted Device Structure
Ruttapol Malatong, Taweesak Sudyoadsuk, Vinich Promarak
A-π-D-π-A type small molecule donors for high performance bulk heterojunction organic photovoltaics
Anthony Maho, Jennifer Dewalque, Gilles Spronck, Audrey Schrijnemakers, Nathan Daem, Pierre Colson, Catherine Henrist, Rudi Cloots
Ultrasonic spray deposition of TiO2 and other semiconducting layers for solar cells and light-driven optoelectronic devices
Wan Li, Praweena Wongkaew, Supawadee Namuangruk, Taweesak Sudyoadsuk, Vinich Promarak
Synthesis and properties of D-π-A-π-D type thiadiazole [3,4-c] pyridine-based small-molecule donors for organic photovoltaics
Hong Lin, Yu Zhou
Enhancing Electron Transport via Graphene Quantum Dot/Tin Oxide Composites for Efficient and Durable Flexible Perovskite Photovoltaics
Takayuki Shimizu, Mitsuhiro Adachi, Akira Suzuki, Rie Watanabe, Mareedu Sreenivasu, Devoju Harinada Chary, Satish Bykkam, Katsuya Tsuchimoto, Junji Nakajima, Toshiyuki Sano, Katsuyoshi Mizumoto
Effects of Modified Phthalocyanine as Hole-Transporting Materials in Perovskite Solar Cells
Mariia Karpacheva, Catherine E. Housecroft, Edwin C. Constable
Electrolyte tuning in dye-sensitized solar cells with N-heterocyclic carbene iron(II) sensitizers
Piotr Piatkowski, Pavel Galar, Thui Tuien Ngo, Mario Gutiérrez, Iván Mora-Seró, Abderrazzak Douhal
Charge carriers transport and recombination in perovskite/PbS quantum dots nanocomposites
Nathan Daem, Jennifer Dewalque, Gilles Spronck, Pierre Colson, Catherine Henrist, Rudi Cloots
Lead-free double perovskite materials for photovoltaic application
Sumita Boonnab, Thanaporn Manyum, Taweesak Sudyoadsuk, Vinich Promarak
D--A--D type small molecules with naphtho[2,3-c][1,2,5]thiadiazole as the central accepting core for organic photovoltaic
Amalraj Peter Amalathas, Lucie Landová, Brianna Conrad, Jakub Holovský
Alkali Lithium Metal Doping Effects on Mesoporous TiO2 Electron Transport Layer Based CH3NH3PbI3 Perovskite Solar Cells
Bosky Sharma, Parag Bhargava, Dinesh Kabra
Enhanced performance of MAPbI3 based solar cell upon addition of p-type molecular dopant
Laura Canil, Thomas Dittrich, Antonio Abate
Work Function Tuning through Self-Assembling Monolayers of Fluorinated Molecules
Silver-Hamill Turren-Cruz, Anders HAGFELDT, Michael Saliba
Methylammonium-free, high-performance, and stable perovskite solar cells on a planar architecture
Mincheol Park, Seung Chan Hong, Mansoo Choi, Junseop Byeon, Yeoun Woo Jang
Continuous Megasonic Spray Coating System for Fabrication of Highly Reproducible Large-area Perovskite Solar Cells
Vinich Promarak, Patteera Funchien, Nakorn Henjongchom, Taweesak Sudyoadsuk
Fuguo Zhang, Licheng Sun
A Facile Route to Grain Morphology Controllable Perovskite Thin Films towards Highly Efficient Perovskite Solar Cells
Somayyeh Gholipour, Parnian Ferdowsi, Michael Saliba
Highly efficient and stable perovskite solar cells via modified carbon back contact
Parnian Ferdowsi, Somayyeh Gholipour, Ullrich Steiner, Michael Saliba
Investigating Wide Band-Gap Perovskite Solar Cells through Interfacial Passivation Using Ultrathin Polymeric Films
Koki Suwa, Kenichi Oyaizu, Hiroshi Segawa, Hiroyuki Nishide
Anti-Oxidizing Perovskite Layer Formation via an Addition of Radical Polymers and its Photovoltaic Cells
Rosie Anthony, Arthur Connell, Leo Furnell, Chris Kershaw, Diana Mesarojas, Eurig Jones, Dawn Geatches, Sebastian Metz, Kakali Sen, Peter Holliman
Surface Engineering of Solid-State Dye-Sensitized Solar Cells
Satoru Seto
Planar heterojunction perovskite solar cells by vapor deposition using hot-wall method
Sofia Masi, Perla Fabiola Mendez Herrera, Salim K.M Muhammamed, Eva Maria Barea Berzosa, Iván Mora-Seró
Planar perovskite solar cells with negligible hysteresis using UVO-treated-SnO2 as electron transporting layer
George Fish, Jacques-E Moser
Probing the Charge Transfer Mechanism in Pentamethine Cyanine Dyes
Marion A. Flatken, Giorgia Greco, Antonio Abate
Structural Properties of Perovskite Layers in High-Performance Solar Cells
Vivek Babu, Rosinda Fuentes Pineda, Taimoor Ahmad, Luigi Angelo Castriotta, Olga Malinkiewicz, Aldo Di Carlo, Konrad Wojciechowski
Flexible p-i-n and n-i-p perovskite solar cells with carbon back electrode
Brener Rodrigo De Carvalho Vale, Andres Burgos-Caminal, Marine Eva Fedora Bouduban, Marco Antonio Schiavon, Jacques-Edouard Moser
Non-Linear Effects in CsPbBr3 Perovskite in a Strong Quantum Confinement Regime
Urs Aeberhard, Stéphane Altazin, Andreas Schiller, Balthasar Blülle, Christoph Kirsch, Evelyne Knapp, Beat Ruhstaller
Numerical optimization of organic tandem solar cells
Alberto Fattori, Maria Claudia Piangerelli, Anna Alessia Viggiano, Maria Francesca Ottaviani
Influence of Co-Adsorption, Co-Sensitization and Dye Extraction on Cells Performance in Natural Dye Sensitized Solar Cells
Antonio Günzler, Sandy Sanchez, Ullrich Steiner, Michael Saliba
Perovskite thin film crystallization with flash infrared annealing (FIRA)
Johannes Küffner, Tina Wahl, Jonas Hanisch, Wolfram Hempel, Erik Ahlswede, Michael Powalla
Blade Coating Perovskite Solar Cells: Impacts of Surfactant in Absorber Layer
Diana Meza-Rojas, Peter J. Holliman, Christopher Kershaw, Rosie Anthony, Eurig Jones, Leo Furnell, Arthur Connell, Ian Matthews
Synthesis and characterization of an organic sensitizer for exploring a new co-sensitization system in dye-sensitized solar cells
Hyeon Jun Jeong, Seongho Bang, Dae Young Park, Hobeom Jeon, Gon Namkoong, Mun Seok Jeong
Low Surface Defect of [111] directional MAPbBr3 Film Formed by Homogeneous Nano-Seeds
Rokas Jasiunas, Vidmantas Gulbinas
Ultrafast Carrier Dynamics in Highly Efficient Nonfullerene Organic Solar Cells
Bernard Wenger, Godding Julian, Snaith Henry
Light Soaking Effects and Passivation in Metal Halide Perovskites
Etienne Socie, Jacques-E. Moser
Broadband Fluorescence Up-Conversion Spectroscopy : A Powerful Tool to Assess Ultrafast Dynamics of Charge Carriers and Excitons in Lead Trihalide Perovskites
M. M. H. Desoky, P. Quagliotto, C. Barolo, M. Bonomo, G. Viscardi, A. Di Carlo, N. Yaghoobi Nia
Synthesis and characterization of different type of Polymers as a potential HTM for Perovskite solar cell
Christopher Bailey, Giacomo Piana, Pavlos Lagoudakis
Phonon-assisted trapping of carriers in lead halide perovskites
Matteo Bonomo, Marco Giordano, Nicole Mariotti, Babak Taheri, Thomas M. Brown, Sergio A. Castro-Hermosa, Giulia Lucarelli, Francesca Brunetti, Claudia Barolo
Polyurethanes as Low Cost and Efficient Encapsulant Materials for Flexible Perovskite Solar Cells
Anthony Houghton, Daryl Williams
Hydration stability of hybrid organic-inorganic halide perovskite powders, single crystals and thin-films by gravimetric water vapour sorption analysis
Manuel Vasquez-Montoya, Daniel Ramirez, Juan F Montoya, Franklin Jaramillo
Scalable Precursor Solution for Stable Perovskite Solar Cells: From Solutions to High-quality Films
Karl-Augsutin Zaininger, Henry J. Snaith
Atomic Layer Deposition for Passivation of Metal Halide Perovskite Materials in Photovoltaic Devices
Christopher Kershaw, Peter Holliman, Eurig Jones, Diana Meza-Rojas, Arthur Connell, Rosie Anthony, Leo Furnell
Stefania Cacovich, Fabio Matteocci, Mojtaba Abdi-Jalebi, Samuel D. Stranks, Aldo Di Carlo, Caterina Ducati, Giorgio Divitini
Unveiling the chemical composition of halide perovskite films using Multivariate Statistical Analyses
Stefan Weber, Rene Nauschnig, Thomas Rath, Gregor Trimmel
Functionalized Perylene Derivatives as Non Fullerene Acceptors for Organic Solar Cells
Laura Schade, Adam Wright, Roger Johnson, Markus Dollmann, Bernard Wenger, Pabitra Nayak, Dharmalingam Prabhakaran, Laura Herz, Robin Nicholas, Henry Snaith, Paolo Radaelli
Structural and Optical Properties of Cs2AgBiBr6 Double Perovskite
Tim Helder, Moritz Schultes, Michael Powalla, Erik Ahlswede
Hydrogenated indium oxide IO:H for semitransparent perovskite cells
Chang-Ming Jiang, Wen-Yu Cheng, Michael Ehrenreich, Gregor Kieslich, Ian Sharp
Charge Recombination Dynamics in Defect-Engineered Organic-Inorganic Halide Perovskites
Sherif Michael
Simplifying the Optimization of Advanced Hybrid Perovskite Photovoltaic Devices, Utilizing A Novel Modeling
Quinten A. Akkerman, Eva Bladt, Sara Bals, Liberato Manna
Fully Inorganic Ruddlesden-Popper double Cl-I and triple Cl-Br-I Lead Halide Perovskite Nanocrystals
Axel Erbing, Hua Wu, Huimin Zhu, Malin B. Johansson, Gabriel J. Man, Soham Mukherjee, Håkan Rensmo, Erik M. J. Johansson, Michael Odelius
Electronic Structure of AgBi2I7 Perovskite: Substitution Effects and Structural Stability
Simone Maranghi, Maria Laura Parisi, Riccardo Basosi, Adalgisa Sinicropi
Methodologies for the sustainability evaluation of innovative renewable energy technologies
Zubin Parekh, Conor Davidson, Matthew Davies, Iain Baikie, Sagar Jain
Understanding the differences between MABiI3 and MAPbI3 under an advanced Kelvin Probe system
Eurig Jones, Peter Holliman, Christopher Kershaw, Arthur Connell, Diana Meza-Rojas, Rosie Anthony, Leo Furnell
Sara Cerra, Raoul Fioravanti, Grigorian Souren, Loreta Angela Muscarella, Ilaria Fratoddi
Electric Behavior of Noble Metal Nanoparticles Based Networks Stabilized by Bifunctional Thiols
Kasjan Misztal, Konrad Wojciechowski, Rosinda Fuentes Pineda
Synthesis, Characterization and Application of Novel Fullerene Derivatives in Perovskite Solar Cells
Vera La Ferrara, Antonella De Maria, Gabriella Rametta, Maria Luisa Addonizio, Marco Della Noce, Lucia V. Mercaldo, Iurie Usatii, Antonio Citarella, Emanuele Calabrò, Enrico Lamanna, Aldo Di Carlo, Paola Delli Veneri
Doped Tin Oxide on Different TCO Electrodes for CH3NH3PbI3 Solar Cells
Jonathan Warby, Henry Snaith
Influence of Composition on Stability of Perovskite Light Emitting Diodes
Yatzil Avalos, Agnès Rivaton, Carmen M. Ruiz, David Duché, Jean-Jacques Simon, Pavlo Perkhun, Olivier Margeat, Christine Videlot-Ackermann, Lydia Cabau, Olivier Bardagot, Renaud Demadrille, Jörg Ackermann
Photodegradation study of ITIC derivatives acceptors and the correlation with stability in organic solar cells2
Agustin Alvarez, Nadja Isabelle Desiree Klipfel, Cristina Roldán-Carmona, Hiroyuki Kanda, Maria Cristina Momblona Rincón, Mohammad Khaja Nazeeruddin, Francisco Fabregat-Santiago
Perovskite Solar Cell Modeling Using Impedance Spectroscopy: Contributions of the Different Resistances to Total Electrical Response.
Ramón Arcas-Martinez, Elena Mas-Marzá, Francisco Fabregat-Santiago, Rafael S. Sánchez
Changes in optical and electrical properties of perovskite associated to temperature
Alberto Fraccarollo, Leaonardo Marchese, Maurizio Cossi
2D and Quasi-2D Lead Organohalide Perovskites with Tunable Band Gap and Enhanced Conductivity
Sebastian Müller
Connection between two models of organic solar cells
Claudia Barolo, Federico Bella, Simone Galliano, Lucia Fagiolari, Matteo Bonomo, Gerrit Boschloo, Michael Graetzel, Claudio Gerbaldi, Guido Viscardi
Optimizing Hydrogel Electrolytes for Dye-sensitized Solar Cells
Luigi Angelo Castriotta, Luigi Vesce, Fabio Matteocci, Aldo Di Carlo
Methyl Ammonium Free Perovskite Solar Cells: an out of Glove Box scalable route towards stability and efficiency
Markus Kohlstädt, O.A. Ibraikulov, J. Wang, N. Leclerc, P. Lévèque, T. Heiser, Uli Wuerfel
ITO-free organic photovoltaic modules based on fluorinated polymers deposited from non-halogenated solution: an important step towards large-scale module production
Hans Köbler, Sebastian Neubert, Boštjan Glažar, Marko Jankovec, Marko Topič, Bernd Rech, Antonio Abate
High-throughput Aging System for perovskite solar cells
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