The unproven durability of perovskite photovoltaics (PVs) is likely to pose a significant technical hurdle in the path towards the widespread deployment of this burgeoning thin-film PV technology. The overall durability of perovskite PVs, which includes operational stability, is directly affected by the mechanical reliability of metal-halide perovskite materials, cells, and modules, but this issue has been largely overlooked. Thus, there is a sense of urgency for addressing the mechanical reliability issue comprehensively, and help perovskite PVs reach their full potential. This presents many challenges, but it also offers vast research opportunities for making meaningful progress towards more durable perovskite PVs. Here I will highlight the important challenges and opportunities, together with best practices, pertaining to the three key interrelated elements that determine the mechanical reliability of perovskite PVs: (i) driving stresses, (ii) mechanical properties, and (iii) mechanical failure. I will also present examples of approaches to mitigate failure and extend the durability of perovskite PVs.  

Mixed tin–lead perovskite materials encounter multiple degradation pathways, limiting their efficacy in tandem photovoltaic technologies. Overcoming these challenges necessitates addressing the thermal instability of the methylammonium cation within the perovskite composition and concurrently enhancing the oxidation resistance of the tin-based component. This study introduces a comprehensive approach to address these limitations, resulting in methylammonium-free tin–lead perovskite solar cells with heightened efficiency and stability. Our methodology involves a multi-component strategy, targeting each constraint. By incorporating cations capable of fine-tuning precursor solution properties, we achieve significantly improved film quality in methylammonium-free perovskites. Concurrently, the integration of reducing agents and surface engineering techniques substantially enhances the robustness and carrier dynamics of the perovskite films. As a testament to the success of our approach, the methylammonium-free perovskite solar cells exhibit an exceptional efficiency exceeding 22%, coupled with significantly enhanced device stability. Remarkably, these devices maintain negligible losses even after over 700 hours of continuous operation under 1 sun illumination. This work underscores the potential of comprehensive strategies in processing delicate materials like tin-containing perovskites, elevating their quality and positioning them for broader, successful applications.

Metal-halide perovskites have been under intense research, for their capability to outperform the single-junction detailed-balance limit through the tandem device architecture by tuning the bandgap via compositional engineering. Mixed lead-tin halide perovskites offer the ideal low bandgap as the bottom subcell for such tandem photovoltaic devices. However, they suffer from various instabilities when exposed to ambient air, comparable to tin-halide perovskites. Mixed lead-tin halide perovskites have been considered to degrade in a manner akin to that of tin-halide perovskites, through formation of tin vacancies and self hole-doping. The differences in the way optoelectronic properties worsen and how trap states develop between FA0.75Cs0.25Pb0.5Sn0.5I3 and FA0.75Cs0.25SnI3 in ambient air were studied and compared in our work, which we present. When exposed to ambient air, both perovskite compositions are subject to optoelectronic degradation through development of trap states, evidenced by the reduction of charge-carrier diffusion lengths. However, it was revealed that deep trap states are formed in lead-tin perovskites during degradation, which deteriorates charge-carrier lifetimes but does not considerably affect charge-carrier sum mobilities. Tin-only perovskites, however, undergo formation of energetically shallow tin vacancy trap states and valence band doping. We also compare the structural degradation in these perovskites. The urge for specific passivation methods for mixed lead-tin iodide perovskites is emphasised in this work. We anticipate such passivation will lead to air stability enhancement, expediting the commercialisation of all-perovskite tandem devices.

Lim, V. J.-Y. et al., Air-Degradation Mechanisms in Mixed Lead-Tin Halide Perovskites for Solar Cells, Adv. Energy Mater. 2023, 13, 2200847

Halide perovskite solar cells have revolutionized the photovoltaic field in the last decade. In a decade of intensive research it has been a huge improvement in the performance of these devices, however, the two main drawbacks of this system, the use of hazardous Pb and the long term stability, still to be open questions that have not been fully addressed. Sn-based perovskite solar cells are the devices presenting the highest performance after Pb-based but significantly below them. In addition, Sn-based perovskite solar cells exhibit a long term stability lower than their Pb containing counterparts, making stability their main problem. In this talk, we highlight how the use of proper additives and light soaking for defect engineering can increase significantly the stability of formamidinium tin iodide (FASnI3) solar cells, and discuss about the different mechanism affecting this stability, beyond the oxidation of Sn2+, and how they can be countered, analyzing specially the light soaking treatment. In addition, the up-scaling of these devices by the use of blade coating introduces new challenges that will be analyzed in this talk. Beyond perovskite solar cells halide perovskite are outstanding for the development of other optoelectronic device, causing that currently the research with these materials widespread to different optoelectronic fields. Preparation and optimization of Sn-based LEDs will be discussed as well as the possibilities of fabrication with industrially friendly methods as inkjet printing.

Organic-inorganic hybrid perovskites (OIHPs) are a fascinating class of semiconductors that can be low-temperature synthesized, crystallized and processed on a large variety of substrates, and at the same time offering outstanding optical and electronic properties, such as broadband spectral tunability, high defect tolerance, high absorption/emission efficiency, room-temperature excitons, etc. These advantages allow OIHPs to complement conventional inorganic semiconductors (e.g., Si and GaAs) in photonics applications that require low-cost, large active area, wide spectral or polarization tunability or flexibility in substrate selection. In this talk I will talk about two OIHP-based photonic devices – photodetector and optically pumped laser. First, I will focus on the commonly seen gain – bandwidth trade-off problem of photodetectors and introduce a monolithically integrated photovoltaic transistor (PVT) design to solve this dilemma. The PVT exploiting a lead halide perovskite as the photoactive layer achieved a record high gain – bandwidth product of ~ 1011. Secondly, I will talk about our recent exploration of using quasi-two-dimensional Dion-Jacobson (DJ) phase perovskites for laser application. With properly selected organic spacers, DJ phase OIHPs offer excellent chemical resistance and thermal processability. These properties allow us to achieve optically pumped perovskite lasers with record-high quality factor, record-low lasing threshold and excellent operational stability.

Nanoparticle supercrystals extend the fascinating properties of colloidal solutions of microscopic quantum dots to the macroscopic realm and are therefore of significant interest for various optoelectronic device applications such as solar cells, LEDs, electro-optic modulators, etc. [1]

We recently reported a study on defect/strain-related optical properties in self-assembled supercrystals of lead halide perovskites. Specifically, reproducibly observed spatial gradients in the photoluminescence energies and lifetimes of CsPbBr₂Cl and CsPbBr₃ supercrystals were shown to result from a combination of compressive strain, a loss of structural coherence, and an increasing atomic misalignment between adjacent nanocrystals. These findings expand on the idea of quantum dots functioning as quasi-atomic building blocks in the formation of macroscopic superstructures. [2]

The presentation will detail the spatially and temporally resolved optical measurements and present current efforts towards understanding and achieving control over the defect-related optical properties through adjustment of parameters both in the synthesis (particle size distribution, surfactant concentration) and the self-assembly (evaporation-method, -time, -temperature) of the nanoparticular building blocks. Furthermore we show that precise and quantifiable mechanical deformations and compressive strain induced by micromanipulators may be used to further explore the relationship between structural and optical properties of these superstructures.

2D multilayered perovskites share similarities with 3D perovskites including direct electronic band gap, sizeable optical absorption, small effective masses, Rashba-like effects. A recent classification of multilayered perovskites as Ruddlesden-Popper, Dion-Jacobson and "Alternative cations in the interlayer" was introduced in relation with the chemistry of the compounds or the crystallographic order along the stacking axis. Interestingly, they exhibit other attractive features related to tunable quantum and dielectric confinements, strong lattice anisotropy, more complex combinations of atomic orbitals and lattice dynamics, extensive chemical engineering possibilities. This will be illustrated by recent combined experimental and theoretical studies on excitons, formation of edge states, hot carrier effects and carrier localization. 2D multilayered perovskites have exhibited improved device stability under operation. More, combined in 2D/3D bilayer structures using new versatile growth methods, excellent solar cell device stability can be achieved. Band alignment calculations nicely explain the difference of performances for ni-p or p-i-n devices. The lattice mismatch concept can provide further guidance for the choice of the proper 2D/3D combination, leading to enhanced stability for 3D-based solar cells.

A perspective into synthesis methods far from thermodynamic equilibrium (i.e., non-equilibrium, NE) and their dependencies with the structure and properties of light-absorbing semiconductors and their devices will be presented. The talk will focus mainly on multinary metal oxides as case study materials using plasma deposition processes combined with rapid thermal processing (RTP).^[1,2] However, the insights are also strongly transferable into metal halide perovskites.^[3,4]

In the research and development of metal oxide semiconductors and a few metal halide perovskites for solar energy conversion, scientists are confronted with two significant challenges: i) the need to exceed normal temperature limits for glass-based F:SnO₂ substrates (FTO, ∼550°C) to achieve the desired density, crystallinity, and low defect concentrations, and ii) avoiding the formation of structural defects, trap states, grain boundaries, and phase impurities, which can be particularly difficult in multinary materials which may contain ions that vary widely in size, oxidation state, and vapor pressure under heating treatment conditions. The unique possibilities of NE synthesis methods can be utilized to form a holistic approach that will overcome these challenges and also provide a broad array of synthesis "tuning knobs" under highly controlled synthesis conditions.

I will demonstrate, using the emerging metal oxide semiconductors for photoelectrochemical water-splitting α-SnWO₄ and CuBi₂O₄, that even subtle changes in synthesis significantly impact material properties, physical working mechanisms, and performances. These materials ' challenges were greatly overcome using the NE synthesis conditions, which were inaccessible through conventional solid-state reactions, with increased crystallinity, conductivity, and device performance.^[1,2,5]

The NE synthesis methods can successfully address a primary need to focus on novel syntheses and design approaches of disruptive and innovative materials and NextGen devices that meet the chemical and physical requirements for reducing global warming through sustainable development.

Metal halide perovskites have achieved impressive energy conversion efficiencies (PCEs)in both single junction and tandem solar cells. However, a key challenge for their practical applications lies in the lower stability of the devices, which is determined not only by the perovskite materials but also by the charge transport layers. Currently, all high-performance perovskite solar cells (PSCs) with > 24% PCE are based on the bench-mark hole transport layer Spiro-OMeTAD, which is doped with lithium bis(trifluoromethane)sulfonimide (LiTFSI) and 4-tert-butylpyridine (tBP), which has a negative impact on the stability of the devices. Moreover, due to the complex in situ oxidation processes, it is difficult to understand the mechanism of conventional spiro-OMeTAD doping, which further limits the development of stable HTLs with high PCEs.

We have developed a clean and free post-oxidation doping for spiro-OMeTAD by using stable organic radicals as the dopant and ionic salts as the dopant modulator (termed ion-modulated (IM) radical doping).¹ The doped Spiro-OMeTAD based on our IM radical doping strategy provided high PCE of over 25% and excellent stability (T80 for ~ 1200 h under 70±5% relative humidity and T80 for ~ 800 h under 70±3 °C without encapsulation), minimizing the trade-off between efficiency and stability of PSCs. In this doping strategy, the radicals provide hole polarons that immediately increase the conductivity and work function, and the ionic salts further modulate the work function by affecting the energetics of the hole polarons. The IM radical doping strategy provides a simple and effective approach to separately optimize the conductivity and WF of organic semiconductors for a variety of optoelectronic applications.

Perovskite Solar Cells (PSCs) have reached impressive performances above 25% in just few years of research.[1] However, there are several factors leading to the limited long-term stability of the PSCs [2], which is still hampering their industrialization. Among them, the highly hygroscopic doping agents, frequently used to increase the conductivity of the hole transporting layer (HTL), accelerate the Perovskite degradation. Hence, the hole transporting materials (HTMs) are now being developed to get high efficiency in the absence or low concentration of these dopants. [3]

In this context, starting from the low-cost phenothiazine and carbazole scaffolds, which are characterized by easily tuneable energetic levels, we synthesised small molecules and polymers through a Suzuki coupling, eventually employing microwaves to promote the reaction yield and selectivity. In the meanwhile, greener synthetic routes have been studied. Once characterized, the materials were implemented in inverted PSCs, which are normally cheaper and more stable than the direct devices. [4] Their performances were studied: the most promising results were obtained with the small molecule A (figure 1), which was able to reach up to 10.96% of Power Conversion Efficiency (PCE) in the optimized conditions (vs 13.07% with the PTAA reference), attesting a high charge extraction. The applied thermal treatments allowed to increase the stability of the devices during the time.

Perovskite solar cells (PSCs) are the most promising PV technology in recent years. Efficiency rocketed from 3.1% to 26% in the last decade. The highest-performing PSCs are lead-based, which increases concerns about the environmental impact of this type of solar cell. Consequently, interest is growing in tin-based PSCs as an environmentally friendly alternative to the lead counterpart. However, tin perovskites are hindered by the tin (II) oxidation to tin (IV), which leads to self-doping and devastating cell performance. DMSO, the universal solvent for tin perovskites, was found to oxidize tin [1]. In our previous work, we introduced a group of 15 different solvents that can form 1 Molar solution of FASnI₃ [2]. However, the film formation dynamics were challenging due to unsuitable coordination between the solvent molecules and the metal, leading to bad micro-structured films. In this work, we introduce a high-throughput screening of 73 antisolvents against the previously introduced solvents to engineer the crystallization dynamics in tin perovskites. Then, we feed the resultant data into a machine learning algorithm with the solvents and the antisolvents parameters to conclude the most related parameters that control the solvent-antisolvent interaction in tin halide perovskites. In addition, the algorithm predicts the most effective solvent-antisolvent pairs that can form a perovskite film based on the film darkness prediction. Furthermore, we use Hansen parameters spheres to explain the relationship between the solvents and the antisolvents that make the highest-performing perovskite film. Finally, we test the most promising tin perovskite films for their efficiency and report a PCE of around 9%, the highest DMSO-free tin halide PSC as far as we know.

Metallic lead is easily formed in films due to decomposition of residual PbI2 in excess lead iodide-incorporated perovskites under light or X-ray irradiation. Pb0 is a typical intrinsic defect which limits mainly the stability of this type of solar cell [1]. A common strategy to heal the defective perovskite is passivation with thiol (-SH) containing ligands which can bind strongly to Pb0 or Pb2+ [2], and reduce directly -or indirectly- Pb0 impurities. Even though a large number of multifunctional compounds, bearing thiol groups, has been tested successfully, there is a lack of consensus on the origins of Pb0 elimination through this approach [3,4].

In this work, we used a model compound, 2-diethylaminoethanethiol (DEAET) in a very low concentration, as a top surface passivator of 10% PbI2 excessive-FAPbI3 and confirmed the enhanced radiative recombination through photoluminescence spectroscopy. XPS analysis has shown a total elimination of Pb0. When depositing DEAT ontop of PbI2 as a reference experiment, XPS revealed a simultaneous down shift for both Pb and I peaks, pointing to a clear chemical interaction of DEAT with PbI2; this interaction causes the disappearance of metallic lead from FAPI films. On the other hand, liquid 1H and 13C NMR, upon titration of DEAT with PbI2, has shown that the starting thiol disappears over time and a disulfide (oxidized form of the thiol) appears; finally, only the complex of PbI2 with the disulfide exists. The findings of this study point to the necessity of understanding the redox chemistry of thiol-based salts that dictates the passivation of PbI2-excessive FAPI perovskite.

Perovskite solar cells currently enter a stage, where market introduction is within reach. For serious upscaling, control over the quality of the perovskite material is most critical. To this end, the community currently relies heavily on laboratory experience, engineering, and fine-tuning approaches. A key challenge is the controlled growth of perovskite crystallites while processing thin films. Several strategies are currently in use, such as like anti-solvent or additive engineering. While the impact of these strategies is well-evidenced in the resulting layers, the underlying mechanisms that govern the crystallization process are still subject to a vigorous debate. A frequently cited theory is that the nuclei for the perovskite crystallization evolve from intermediate Pb²⁺-MA⁺-I^--solvate clusters. [1] A dominant role of solvate clusters implies a strong impact of complexing and coordination in the precursor solution on the crystallization process. Reports of the colloidal structures and Lewis-base-acid interactions in the perovskite precursor ink seemingly support this theory. [2] As of yet, however, insights that unambiguously link the complex formation in the precursor inks to the perovskite formation are lacking.

We present a holistic approach in which we study the entire course of perovskite formation. We begin with as study of lead complexation in the precursor stage (using NMR and electrical conductivity measurements in the solution) and proceed with in-situ GIWAXS investigations during thin film deposition and along the way to thin film formation (bare layers and solar cells). We systematically study the impact of common solvents like DMF, DMSO and NMP. As an exemplary additive, to study the influence of Lewis-base additives, we chose thiourea, which is a strong sulphur donor and an effective crystallization mediator. With ²⁰⁷Pb NMR and conductivity studies, we found a strong and systematic impact of the choice of solvents on the formation of lead complexes in the precursor solution, as well as indications, that suggest the presence of 3D corner sharing structures already in the precursor ink. Importantly, the differences in lead complexation depending on the solvent apparently diminish with increasing the concentration of the precursor ink; the final grain sizes remained largely unaffected by even strong variations found in the diluted precursors. On the other hand, the addition of thiourea did not affect the nature of lead complexes in the precursor solution. By in-situ GIWAXS, we are finally able to identify the annealing step as the decisive stage, where the presence of the additive affects the formation of perovskite grains and their crystallographic orientation. We could further substantiate our interpretation by FTIR studies. As such, for the first time, we provide a convincing link (or the lack thereof) between precursor chemistry and final thin film formation.

Metal halide perovskite crystals in the macro and nano scales can leverage the huge versatility of the perovskite family. They present exceptional optoelectronic properties that make them attractive for a variety of applications. However, these structures usually depend on complex synthesis processes, where the ligands play a dominating role, or are limited by growth form factor and surface losses.
We present crystallization insights that enable less demanding synthesis processes, such as a promising sol-gel approach [1] for humidity-triggered nanoparticle crystallization or a contactless surface passivation technique for large crystals. The particularity of these systems can be adapted to specific applications such as memristive devices or downconversion films with efficiencies >95%, which also serve as a platform to characterize the fundamental working mechanisms of these materials.
The combination of the crystallization control with additive engineering also opens new routes for lead-free perovskite photovoltaics, improving their ambient and operational stabilities.

 

Three-dimensional (3D) organic–inorganic lead halide perovskites have emerged in the past few years as a promising material for low-cost, high-efficiency optoelectronic devices. Spurred by this recent interest, several subclasses of halide perovskites such as two-dimensional (2D) halide perovskites have begun to play a significant role in advancing the fundamental understanding of the structural, chemical, and physical properties of halide perovskites, which are technologically relevant. While the chemistry of these 2D materials is similar to that of the 3D halide perovskites, their layered structure with a hybrid organic–inorganic interface induces new emergent properties that can significantly or sometimes subtly be important. Synergistic properties can be realized in systems that combine different materials exhibiting different dimensionalities by exploiting their intrinsic compatibility. In many cases, the weaknesses of each material can be alleviated in heterostructures. For example, 3D-2D halide perovskites can demonstrate novel behavior that neither material would be capable of separately.

In this talk, I will describe several examples of how synergistic properties between 3D and 2D give rise to emergent materials properties. I will describe the impact of deterministically combining 3D and 2D heterostructures on long-term durability, and stabilizing FAPbI3 without MA, Cs or Br, with >24% photovoltaic efficiency in a p-i-n architecture and also exceptional durability under 85 C, continuous AM1.5 illumination at MPPT.

Recent advancements in halide perovskite photovoltaics have brought power conversion efficiencies to levels suitable for commercial use. Despite these advances, the durability of these devices is a major challenge that needs further improvement. A notable development in this area is the use of Ruddlesden-Popper (RP) two-dimensional (2D) perovskite layers on top of traditional three-dimensional (3D) perovskite active layers, enhancing the stability of perovskite solar cells (PSCs) [1-2]. While there have been several reports of efficient and stable PSCs using 2D/3D heterojunctions [3-4], the detailed interactions at the 2D/3D interface are not fully understood. Understanding the relationship between the atomic structure at this interface and electron behavior is essential to comprehend the effectiveness of these methods and to optimize the benefits of interface engineering. In this work, we used density-functional theory (DFT) calculations to explore how the atomic arrangement at interfaces influences the characteristics of 2D/3D halide perovskite heterojunctions. Our findings indicate that the thermodynamic stability and band alignment of these heterojunctions are significantly influenced by the arrangement of Cs/PEA cations at the interfaces.

Two-dimensional (2D)-based passivation on three-dimensional (3D) perovskite layers has made great progress in enhancing the efficiency of perovskite solar cells, though 2D/3D has worse operational stability than 2D or 3D alone at elevated temperatures due to the severe ion migration and enhanced reactivity with formamidinium (FA⁺) [1-3]. It still remains mysterious in terms of how 2D/3D worsens device performance by altering device physics under heat and light soaking conditions. In this work, 11 kinds of ligands are chosen to passivate perovskite films with different concentrations and degraded under 3 ageing conditions (25℃-light, 85℃-dark and 85℃-light). Most of the 2D perovskite signals disappear after 85℃-light degradation. An unexpected absorbance upshift occurs for most of the passivated perovskite films after light soaking, which is attributed to light scattering by an undesirable phase of metallic lead (Pb⁰) decomposed continuously from lead iodide (PbI­₂) during light soaking. We find that it is ligands such as phenethylammonium (PEA⁺), which form the Ruddlesden-Popper (RP) phase, that accelerate the production of PbI­₂, which in turn produces more Pb⁰ and iodine (I₂) in the presence of light or heat-light. Dion-Jacobson (DJ) and alternating-cation-interlayer (ACI) phases, in contrast, decelerate the production of Pb⁰ and I₂. By choosing the proper ligand and passivation method, we have successfully fabricated ultra-stable solar cell, retaining 80% of its initial performance after 550 hours under 85℃ and two-sun illumination.

Three-dimensional (3D)/low-dimensional (LD) perovskite solar cells (PSCs) offer an effective strategy to overcome the trade-off between perovskite solar cells device performance and stability. Improving the device longevity, while concomitantly simultaneously enhancing increasing the solar cell open circuit voltage and fill factor of the solar cell is the current challenge. Despite being one of the most popular and effective way processing techniques, whether the presence of this surface LDP layer would be - or not-represents the winning crucial path for the future of this technology remains elusive. In particular, atomic layer combined surface and bulk passivation using surface modifiers such as organic dopants, casts the doubts on the effective need for of having an homogeneous LDP cover capping layer. In this talk, I will discuss the interfacial passivation with different cations such as M-PEAI, M-PEABr, and M-PEACl, showing the role of the passivation and how different halides affect the device performance of the devices. In addition, I will compare recent results obtained in the 3D/LDP configuration with the surface cation passivation strategy, which can still pushes produce the performances to values comparable to the LDP/3D bilayers. I will providing a comprehensive perspective on the benefits from of the two different strategies, but also presenting how LDP interfaces can play a role in alternative new configurations, such as tandem solar cells.

Inter alia, the application of 2D phenylethylammonium lead quaternary iodide (PEA₂PbI₄)/three-dimensional (3D) metal halide perovskite (MHP) interfaces has improved various optoelectronic devices, where a staggered type-II energy level alignment was often assumed. However, a type-II heterojunction seems to contradict the enhanced photoluminescence observed for 2D PEA₂PbI₄/3D MHP interfaces, which raises fundamental questions about the electronic properties of such junctions. Using direct and inverse photoelectron spectroscopy, we reveal that a straddling type-I energy level alignment is present at 2D PEA₂PbI₄/3D methylammonium lead triiodide (MAPbI₃) interfaces, thus explaining that the photoluminescence enhancement of the 3D perovskite is induced by energy transfer from the 2D perovskite.

On another note, formamidinium lead triiodide (FAPbI₃) is gaining attention as a perovskite solar absorber due to its close to optimal bandgap for single-junction solar cells and enhanced thermal stability compared to many other MHPs. However, in order to achieve the stable black-phase FAPbI₃, a relatively high temperature annealing (150 °C) is required. Recent studies have highlighted the impact of high-temperature annealing on FAPbI₃ crystal structure originating from lattice distortion and volume expansion. Nonetheless, the fundamental understanding of its electronic properties remained unclear. Here, we show that intrinsic iodine vacancies lead to n-type character, and that in-diffusing oxygen can fill iodine vacancies, leading to a Fermi level shift towards the valence band by about 0.5 eV. Furthermore, we demonstrate how the energy levels at interface to charge selective contacts can be controlled by doping, and how this influences the quasi-Fermi level splitting under illumination due to charge accumulation at the interface.

In typical stability studies, perovskite solar cells (PSC) are tracked at its maximum power point (MPP) under continuous or cycled illumination at elevated temperature to simulate outdoor conditions. MPP decay curves evolve differently on different device configurations, depending on the perovskite composition, the selective contact materials or even batch-to-batch variations. Having a better understanding of the complex mechanisms that cause the performance decay at different timeframes is key for the future development of PSCs. In this work we propose a non-destructive method that can be used quasi in-situ along the MPP to gain additional information on the evolution of various mechanisms that govern the device efficiency, beyond merely measure JV curves. We analyzed several PSC devices with electrochemical impedance spectroscopy (EIS) and steady-state- and time-resolved- photoluminescence (PL/TRPL) before and after different stages of its MPP tracking and show the consecutive changes of multiple parameters including shunt resistances, recombination, ionic density/kinetics and formation of barriers and propose a model on the evolution of the degradation. We also show the importance of analyzing statistically-significant number of samples to account for the intrinsic –uncontrolled- variability existing within a batch.

This talk will explore the use of carbon electrodes in the fabrication of perovskite solar cells via a high-volume continuous slot-die roll-to-roll (R2R) method, discussing both the opportunities and challenges this technology presents.

A key aspect of the presentation will be the development and application of a specialized carbon ink in the R2R process. This ink is crucial for creating an efficient and compatible electrode layer in perovskite solar cells. However, the integration of carbon into the tightly controlled sequence of the R2R process presents significant challenges. Achieving uniform deposition of the carbon layer at the same processing speeds as other layers requires precise control over the rheology and drying behavior of the ink. These factors are critical to maintain the efficiency and consistency of the solar cells.

One of the major hurdles in this process is ensuring that the carbon ink can be deposited seamlessly within the high-speed, continuous R2R process without compromising the quality of the perovskite layer. Achieving this requires an understanding of the material properties and the interaction between the different layers of the solar cell.

The talk will also address the broader vision of this technology. The ultimate goal is to realize the concept of "liquid in, solar cell out," where the entire solar cell, from the transport layers to the perovskite layer to the carbon electrode, is fabricated in a single, continuous process. This approach promises not only a reduction in production costs but also a significant increase in the scalability and accessibility of perovskite technology.