The surface chemistry of colloidal lead halide perovskite nanocrystals is remarkably rich. The chemically labile surfaces of these nanocrystals can be functionalized with a wide variety of ligands, some enhancing stability against degradation, others improving physical properties, or even imparting new functionalities. Because nanocrystals serve as building blocks for emergent materials, systematically varying their surface ligands offers a powerful route to study structure-property relationships across nanocrystal-based materials. This approach applies not only to nanocrystal dispersions, thin films, and composites, but also to ordered nanocrystal assemblies (superlattices). For example, depending on the assembly method, such as slow solvent evaporation or antisolvent diffusion, CsPbBr3 perovskite nanocrystal superlattices can exhibit markedly different mechanical and structural characteristics. In this talk, I will discuss our efforts to understand how mixed-ligand surface chemistry governs the stability and structural order of CsPbBr3 perovskite nanocrystal superlattices, and how these insights can inform the design of robust, functional nanocrystal solids.[1]

Mixed-halide perovskites are ideal mid- and wide-gap absorbers for multi-junction solar cells, but stable photovoltaic performance is severely compromised by halide segregation. Herein, we utilise a fine-grained compositional approach to investigate differences in the initial formation and photoinduced segregation of CH₃NH₃Pb(I_1-xBr_x)₃.^[1] Our multimodal spectroscopic approach, combining in-situ X-ray diffraction (XRD) and photoluminescence (PL) tracking, further allows the applicability of PL spectroscopy as a measure of halide segregation to be evaluated – a pertinent step given the near-ubiquitous use of this probe technique in the development of photostable mixed-halide absorbers.

X-ray diffractometry across stoichiometries spanning twenty-two bromide fractions demonstrates that central compositions near x = 0.5 form two macrostrained phases (in the dark), which may compensate for the detrimental difference in the iodide and bromide ionic radii and cause the absence of a theoretically predicted miscibility gap.^[2] Via in-situ XRD under illumination, we find that such macrostrained phases exhibit halide segregation at different rates, highlighting how initial strain engineering can modulate the speed of segregation. Alongside material strain, we provide experimental verification that halide ordering also influences segregation: CH₃NH₃PbIBr₂ is found to exhibit exceptional segregation resistance, as theoretically predicted.^[2] Combining structural and optical probes, we further demonstrate that halide segregation does still occur below the widely-quoted threshold of x equal to 0.2.

Strikingly, we find that whilst the structurally-determined segregation rate is broadly constant across the entire compositional space examined, suggesting that the mobility of halide ions dictates the rate of segregation, the rate extracted from in situ photoluminescence measurements rises over four orders of magnitude with increasing bromide fraction. We resolve this disparity by analysis of the energetics and luminescence efficiency of recombining charge carriers, evidencing how such underlying (photo)physics can lead to artificially accelerated segregation rates determined from PL measurements.

Together, our results provide a multitude of new evaluation benchmarks for proposed models of phase segregation, while also highlighting new routes for developing segregation resistant absorber layers via the engineering of macrostrained phases and local atomistic ordering. Furthermore, our multimodal spectroscopic approach demonstrates that photoluminescence, the most widely used spectroscopic tool in such investigations, is not an appropriate probe of halide segregation, and should be supplemented by average-structure-sensitive techniques.

Wide-bandgap metal-halide perovskites are increasingly recognized as key absorber materials for tandem photovoltaic architectures and indoor energy-harvesting devices. Nevertheless, their performance is still hindered by non-radiative recombination, interfacial defect states, and illumination-induced halide segregation, all of which contribute to voltage losses and reduced operational stability. In this work, we introduce an integrated passivation approach that combines tailored molecular surface modifiers with engineered interlayers, specifically optimized for bromide-rich wide-bandgap perovskite compositions.

We systematically examine the impact of these passivation strategies under both AM1.5 solar irradiation and low-intensity artificial illumination, enabling a direct evaluation of their effectiveness across different lighting conditions. Comprehensive characterization, including trap-density measurements, steady-state and time-resolved photoluminescence, absorption analysis, and continuous-illumination stability testing, reveals that the optimized surface and interfacial passivation significantly reduces trap-assisted recombination, suppresses halide segregation, and enhances the optoelectronic quality of the perovskite films. As a result, the corresponding devices exhibit notable improvements in open-circuit voltage, fill factor, and long-term operational durability relative to untreated controls.

Overall, this study establishes an illumination-robust passivation methodology for wide-bandgap perovskites and provides practical guidelines for the development of high-efficiency, stable devices suitable for both tandem photovoltaic systems and indoor energy-harvesting applications. These insights contribute to the broader understanding of defect mitigation and interface engineering in wide-bandgap perovskite absorbers.

Defect passivation is a widely used strategy to improve the stability of hybrid perovskites, yet its impact on the optical properties of MAPbBr₃ remains insufficiently understood. In this work, we employ ab initio computational modeling to investigate how different surface modifications influence both the stability and optical behavior of MAPbBr₃ perovskites. We compare the pristine material with systems containing bromine vacancies, as well as structures passivated with hydroxide (OH⁻) and acetate molecules adsorbed on lead and bromine sites.

Our results show that bromine vacancies significantly destabilize the material, confirming their detrimental role in perovskite performance. Passivation with OH⁻ groups provides only limited stabilization and induces only minor changes in the optical properties. In contrast, acetate molecules strongly enhance the energetic stability of MAPbBr₃, indicating efficient passivation of defective sites; however, this increased stability is accompanied by a degradation of the optical properties, suggesting an unfavorable alteration of the electronic states responsible for light absorption and emission.

Notably, recent experimental work by Abargues, Boix et al. [1] reported a synergistic stabilization effect of OH⁻ and AcO⁻ anions in MAPbBr₃ nanocrystals embedded in a Ni(AcO)₂ matrix, where the combined coordination environment promotes effective defect passivation and a significant reduction in trap-state density. This observation suggests that cooperative interactions between multiple functional groups and metal–acetate complexes may mitigate the stability–optical performance trade-off observed when individual passivating agents are considered separately.

Overall, these findings highlight the delicate balance between structural stability and optical performance in defect-passivated MAPbBr₃ and underline the importance of passivation strategies to optimize perovskite optoelectronic materials.

The stability of perovskite materials remains one of the central challenges for their practical implementation. While lead halide perovskites often degrade under mild thermal or environmental stress, our recent work on their metal-free analogues reveals a very different picture. These fully molecular perovskite frameworks, composed entirely of organic cations and halide anions, display an unexpected structural resilience that challenges common assumptions about the fragility of organic lattices.

In this talk, I will discuss how mechanosynthesis, i.e., the solvent-free synthesis of solids through controlled mechanical impact, acts not only as a sustainable preparation method but also as a tool to encode different structural states and defect landscapes into MFPs. By tuning the milling frequency, we access materials with distinct microstrain and metastability, whose responses to temperature reveal the interplay between processing history and intrinsic lattice resilience.

Temperature-dependent synchrotron X-ray diffraction (T-XRD) and differential scanning calorimetry (DSC) provide complementary perspectives on these transformations. The diffraction data show that mechanochemically generated strain strongly influences the thermal evolution of DABCONH₄X₃ (X = Cl, Br, I): samples produced under lower-energy milling undergo cooperative phase rearrangements on first heating, whereas those prepared at higher energy relax gradually through defect annealing and domain coarsening. Despite these transformations, the perovskite frameworks remain crystalline and recover their symmetry without decomposition.

Subtle variations in peak broadening and line-shape asymmetry indicate microstructural healing rather than breakdown, pointing to hydrogen-bond-mediated flexibility as a stabilizing factor. Together, these results highlight mechanosynthesis as a powerful platform for directing phase stability and show that all-organic perovskites can be more resilient than expected, an observation that redefines the boundaries of structural robustness in organic-based perovskite materials.

As perovskite solar cells approach maturity, commercially viable production processes are desirable but record efficiency perovskite solar cells from research labs are predominantly deposited by non-scalable methods [1]. In addition to scalability, stability is a challenge [2]. Therefore, this study analyses the thermal and photothermal stability of co-evaporated (FA_0.82,Cs_0.18)Pb(I_0.89,Br_0.11)₃ perovskite films through several imaging and characterisation methods. Samples have been encapsulated to avoid excessive exposure to atmosphere. Since the films are deposited on Indium tin oxide/Me-4PACz, the crystallisation and deposition procedures mimic those in full stack solar cells. The effect of 1000 hours degradation in 85°C, with or without light exposure, is investigated with optical microscopy, hyperspectral and normal photoluminescence imaging, X-ray diffraction, time-resolved fluorescence imaging and electron microscopy. As-deposited films are found to have both micro-meter sized optically transparent clusters, in addition to red-shifted bright photoluminescence spots with lower bandgap, both possibly caused by non-uniformities in elemental distribution due to a locally different substrate or spitting. While heat does not cause any significant growth of these clusters, the grain size of the heated sample is substantially reduced. The quasi-Fermi level splitting is, however, unaffected by the heating, while the lifetime is cut by half, compared to the non-heated references. The observation of reduced grain size is in conflict with other studies [3] and may point to different degradation patterns in vacuum processed compared to solution processed perovskite solar cells. In agreement with [3], we find that the combination of heat and light is detrimental with severe cation, but in our case also halide segregation. The Me-4PACz layer is still intact and some cubic and photoactive perovskite is still present, although with reduced quality. Transparent patches of δ-CsPb(I,Br)₃ perovskite are identified by X-ray diffraction, energy dispersive X-ray spectroscopy mapping and UV-vis spectroscopy in the heated-light soaked samples. Identification of other chemical compounds is not feasiable due to complexity of the segregation. We have evidenced a clear difference in degradation mechanisms between light and heat exposed samples and those kept in the dark, while the mechanisms themselves have not yet been elucidated at this point. 

Quantum Dot Space is a new open-access platform designed to streamline the design, exploration, and sharing of quantum-dot (QD) structures and passivation schemes. Using the integrated QD Builder, users can upload a core geometry (.cif or custom), tune size, aspect ratio, crystal facets, shells, and ligand passivation to build fully passivated nanocrystals ready for simulation or visualization. Complementing the builder, the curated QD Library hosts a growing collection of pre-computed QD structures across material classes, sizes, and functionalizations — all downloadable and viewable in 3D, with metadata including stoichiometry, facet configuration, and ligand distributions. Quantum Dot Space thus accelerates computational-materials workflows, promotes reproducibility, and fosters collaborative sharing of QD data. In this talk, I will present the platform’s design philosophy, demonstrate how to build and retrieve QDs, and discuss how this resource can support ML-FF training, high-throughput screening, and community-driven QD research.

As perovskites near the realm of commercialization, there are still so many unknowns about microscopic effects within the perovskite layer and within the overall device stack. In a typical PIN single junction perovskite solar cell, the hole transport layer (HTL) plays a critical role in serving as the template for which the perovskite crystalizes upon in addition to its intended job to extract the positively charged carriers. At this stage, there are a variety of material classes being used effectively in PIN solar cells including metal oxides, molecular layers and polymers. In this presentation, we will explore the role that these different classes of materials play in the function and stability of perovskite solar cells. In addition, the synergy of multiple HTLs can provide better extraction and stability. We will describe the interplay of double HTLs. On the top surface of the perovskite, passivation and the interface between perovskites and the fullerene are one of the weakest layers in the device design but also show the biggest potential for improvement. We explore stengthening strategies and alternative materials from the traditional C60/BCP combination.

Metal halide perovskites (MHPs) continue to redefine the landscape of solution-processed optoelectronics, yet their implementation remains hindered by instability, compositional fragility, and stringent synthesis requirements. This invited contribution presents an unconventional in situ synthesis framework that directly generates perovskite nanocrystals (NCs) within reactive inorganic–organic matrices under ambient, glovebox-free conditions.

The method exploits metal–organic scaffolds to guide NC nucleation and growth, enabling precise control over composition, dimensionality, and defect passivation across a broad range of halide (Cl⁻, Br⁻, I⁻) and A-site (Cs⁺, MA⁺, FA⁺) chemistries. The resulting nanocomposites display exceptional environmental stability, strongly suppressed defect densities, and near-unity photoluminescence quantum yields in selected systems. Incorporation of bulky organic cations extends the approach to low-dimensional and 0D lead-free perovskites, including highly robust Sn-based phases and Ag/Bi double-perovskite nanocrystals such as Cs₂AgBiBr₆, which additionally exhibit promising photocatalytic responses. [1-5]

Because the chemistry proceeds at room temperature and is inherently compatible with roll-to-roll deposition, the platform provides a scalable and sustainable route for large-area perovskite manufacturing. Its reproducibility and tunability also make it well suited for automation and machine-learning-assisted discovery. Demonstrated applications span photovoltaics, LEDs, lasing [6], down-conversion, photocatalysis [4], and gas sensing, showcasing the potential of in situ synthetic design to expand the functional space of perovskite nanomaterials and enable new device architectures.

Low-demanding in situ crystallization method for tunable and stable perovskite nanoparticle thin films. J. Noguera-Gomez, I. Fernandez-Guillen, P. F. Betancur, V. S. Chirvony, P. P. Boix, R. Abargues. Matter, 2022, 5, 3541-3552. https://doi.org/10.1016/j.matt.2022.07.017

Protocol for the synthesis of perovskite nanocrystal thin films via in situ crystallization method J. Noguera-Gómez, P. P. Boix, R. Abargues. STAR Protocols, 4 (4), 102507 (2023). https://doi.org/10.1016/j.xpro.2023.102507

Passivation Mechanism in Highly Luminescent Nanocomposite‐Based MAPbBr3 Perovskite Nanocrystals. J. Noguera‐Gómez, V. Sagra, V. S. Chirvony, M. Minguez‐Avellan, M. E. Changarath, J. F. Sánchez‐Royo, J. P. Martínez‐Pastor, P. P. Boix, R. Abargues. Small Science 2025. 2400529. https://doi.org/10.1002/smsc.202400529

Perovskite Nanocomposite: A Step Toward Photocatalytic Degradation of Organic Dyes. M. Minguez-Avellan, N. Farinós-Navajas, J. Noguera-Gómez, V. Sagra-Rodríguez, M. Vallés-Pelarda, C. Momblona, T. S. Ripolles, P. P. Boix, R. Abargues. Sol. RRL 2024, 8, 2400449 https://doi.org/10.1002/solr.202400449

Chemically driven dimensionality modulation on hybrid tin (II) halide perovskites microcrystals
R. I. Sánchez-Alarcón, O. E. Solís, M. C. Momblona-Rincón, T. S. Ripollés, J. P. Martínez-Pastor, R. Abargues, P. P. Boix. J. Mater. Chem. C, J. Mater. Chem. C, 2024, 12, 7605-7614. https://doi.org/10.1039/D4TC00623B

Photon Recycling Triggered Amplified Spontaneous Emission in MAPbBr3-Ni(AcO)2 Nanocomposite Waveguides S. Soriano-Díaz, J. Noguera-Gómez, J. P. Martínez-Pastor, P. P. Boix, R. Abargues, I. Suárez. Laser & Photonics Reviews 2025 https://doi.org/10.1002/lpor.202401920

Perovskite solar cells (PSCs) have rapidly reached power conversion efficiencies comparable to those of established photovoltaic technologies, highlighting the critical need to understand their operational and long-term stability for successful commercialization. Despite this importance, many stability evaluations are performed under short, non-standardized conditions, producing data that are difficult to compare or interpret across different studies. Moreover, the unique physicochemical behavior of perovskites often warrants aging protocols that extend beyond conventional photovoltaic qualification procedures. In this study, we investigate the influence of extended storage on the intrinsic aging behavior of PSCs over a period of three years. Devices with a Glass/FTO/compact-TiO₂/mesoporous-TiO₂/perovskite/Spiro-OMeTAD/Au configuration were fabricated and stored in a nitrogen-filled glovebox, ensuring that observed degradation stemmed solely from internal material and interfacial processes rather than external environmental factors. Over the three-year storage period, the power conversion efficiency (PCE) decreases markedly from 17% to 8%. Comprehensive material and device characterization reveals that this performance loss is primarily driven by gradual decomposition of the perovskite absorber layer, as confirmed through X-ray diffraction (XRD) and time-of-flight secondary-ion mass spectrometry (ToF-SIMS). Importantly, the long-term aging also leads to pronounced lead (Pb) diffusion toward the metallic electrode, indicating progressive interfacial reactions at the perovskite/contact boundary. Photoluminescence measurements show substantial quenching of the emission signal, further evidencing the formation of non-radiative recombination sites associated with defect generation and ion migration. These findings provide deeper insight into the intrinsic durability limitations of PSCs, even under inert storage conditions, and identify key degradation pathways that must be addressed through improved absorber compositions, interface engineering, and encapsulation strategies. Ultimately, this work contributes toward establishing reliable long-term stability benchmarks and offers valuable direction for advancing PSCs toward scalable and commercially robust photovoltaic technologies.

Herein, we present a comparative study of different solution-based and solution-free zinc oxide deposition methods in the context of their impact on the stability of ZnO/perovskite interface using a series of complementary experimental and computational methods. Thus, it has been revealed that the OH-terminated oxide surface induced severe degradation of all types of perovskite absorbers. The zinc oxide passivated from the surface with acetate groups was found to be very aggressive toward MAPbI₃ and quite inert with respect to a methylammonium-free perovskite formulation. Most notably, the amine-passivated ZnO films induced no degradation of the perovskite absorber films, whereas the corresponding perovskite solar cells retained 70% of the initial efficiency after 2500 h of continuous operation under open circuit conditions and white light irradiation, which is an impressive result for devices with n-i-p geometry. Thus, the presented results demonstrate the power of the surface chemistry that can alter completely the behavior of the ZnO films; this approach holds a great potential for tailoring the properties of other oxide materials such as TiO₂, SnO₂, NiO, etc. to pave a way to efficient and stable perovskite solar cells.

Since perovskite solar cells (PSCs) were introduced to the photovoltaic (PV) field, research has predominantly focused on increasing their power conversion efficiency (PCE), achieving values comparable to state-of-the-art silicon technologies available on the market. Progress in extending long-term stability has followed, with devices often reaching t₈₀ values of several hundred hours; nevertheless, further improvements in long-term stability and understanding of degradation mechanisms are needed for commercialization.

PSCs degradation can be triggered by external factors such as UV light, temperature, and humidity, which cause ion migration given the ionic nature of perovskite. Here, adjacent layers play an important role in preventing metal ion diffusion and passivating the interface between the perovskite and charge transport layers. Electron transport layers (ETLs) based on fullerene (C₆₀) and its derivatives offer high electron mobility and reduced hysteresis; however, C₆₀-derivatives permeability allow ionic diffusion, leading to low stability.[1] The uniform characteristics of atomic layer deposition (ALD) enable the deposition of compact and pinhole-free materials. TiO₂, SnO₂, and ZnO are typical ETL candidates due to their band alignment, with SnO₂ remaining one of the preferred options. ZnO, which can serve as a blocking ion layer [2], has, perhaps unjustifiably, gradually fallen out of favor as it accelerates perovskite degradation when in direct contact due to its hygroscopic nature.[3], [4]

In this work, we demonstrate that incorporating ZnO films deposited by ALD into inverted PSCs improves long-term stability under continuous illumination. ZnO can act alone or in addition to SnO₂, on top of C₆₀. The latter case is especially important, as the use of ALD bilayers SnO₂|ZnO combines the higher power efficiency of SnO₂ with the improved stability provided by ZnO. The long-term stability of ZnO-containing cells improves by a factor of 2–3 compared to our reference cells, as confirmed by analyzing numerous (> 100) devices over several batches. In the best case, a t₈₀ of over 1100 hours has been reached. Several techniques, such as TEM, XPS, EQE, and PLQY, were used to elucidate the role of ALD ZnO films in improving stability.

Metal halide perovskites (MHPs), as emerging optoelectronic materials for photovoltaic devices (PVs), light-emitting diodes (LEDs), and photodetectors, have demonstrated remarkable potential for breakthrough developments. Despite these advances, the long-term operational stability, a persistent challenge across all perovskite-based optoelectronic applications, continues to impede their rapid commercialization. For perovskite solar cell, combined light and thermal stress represent the dominant intrinsic degradation factors, while failures related to oxygen and humidity have been largely mitigated through encapsulation^[1].

Increasing evidence suggests that the early-stage performance collapse is not associated with the deterioration of charge generation dynamics or the formation of deep electronic traps, as long as the perovskite maintains its structural and compositional integrity. It appears that charge transport and extraction are the limiting factors that need to be resolved within the entire photovoltaic conversion pathway.

Here, we demonstrate two distinct modes of collapse in the charge transport and extraction processes during aging: a “bias-sensitive mode” (Me-4PACz-based cells) and a “bias-independent mode” (PTAA-based cells). Mechanistic studies reveal a direct correlation between charge/ion dynamics under different bias conditions and material evolution, highlighting the critical roles of ion redistribution and interfacial charge accumulation in governing device stability.

Based on these insights, we developed interfacial strategies targeting both charge-transport interfaces. At the bottom interface, a solvent-vapor-annealed small-molecule/polymer blended hole transport layer (Blend_SVA) was introduced to suppress mobile-ion generation and mitigate field screening. This approach significantly enhanced long-term operational stability under continuous full-spectrum illumination at 70 ± 5 °C and open-circuit conditions, achieving average and champion T80 lifetimes of 1,370 h and 1,570 h, respectively. At the top interface, amino-silane passivation molecules (AEAPTMS) effectively preserved perovskite crystallinity, suppressed non-radiative recombination, and extended device durability, with average and champion T80 values of approximately 1,100 h and 1,600 h under the same aging conditions^[2]. When both interfacial strategies were combined, the resulting perovskite solar cells exhibited remarkable post–burn-in stability, with average and champion T80 lifetimes of 2,839 h and 4,358 h under identical stress conditions.

This work elucidates interfacial dynamics underlying degradation and presents design guidelines toward stable perovskite optoelectronics.

Perovskite-organic tandem solar cells (P-O TSCs) hold great promise for next-generation thin-film photovoltaics, with steadily improving power conversion efficiency (PCE). However, the development of optimal interconnecting layers (ICLs) remains one major challenge for further efficiency gains, and progress in understanding the improved long-term stability of P-O tandem configuration has been lagging. In this study, we experimentally investigate the enhanced stability of p-i-n P-O TSCs employing a simplified C₆₀/atomic-layer-deposition (ALD) SnO_x/PEDOT: PSS ICL without an additional charge recombination layer (CRL), which achieve an averaged efficiency of 25.12% and a hero efficiency of 25.5%. Our finding discovers that the recrystallization of C₆₀, a widely used electron transport layer in perovskite photovoltaics, leads to the formation of grain boundaries during operation, which act as preferential migration channels for the interdiffusion of halide and Ag ions. Critically, we demonstrate for the first time that the tandem device architecture, incorporating organic semiconductor layers, effectively suppresses the bi-directional ion diffusion and mitigates electrode corrosion. Thus, the P-O TSC establishes a mutual protection system: the organic layers stabilize the perovskite sub-cell by suppressing ion diffusion-induced degradation, and the perovskite layer shields the organic sub-cell from spectrally induced degradation. The simultaneous synergistic protection mechanism enables P-O TSCs to achieve exceptional long-term operational stability, retaining over 91% of their initial efficiency after 1000 hours of continuous metal-halide lamp illumination, and to exhibit minimal fatigue after 86 cycles (2067 hours) of long-term diurnal (12/12-hour) testing. These results demonstrate that tandem cells significantly outperform their single-junction counterparts in both efficiency and stability.

Perovskite solar cells (PSCs) are rapidly approaching commercialization due to their high efficiency and low manufacturing cost. To ensure their deployment aligns with circular economy principles, recycling pathways must be integrated before large-scale adoption to avoid repeating the non-recyclable waste challenge of silicon photovoltaics. Although several studies have demonstrated the recovery of individual perovskite layers, full device recycling remains hindered by encapsulation and sealing materials designed for permanence. Conventional cross-linked encapsulants and polyisobutylene (PIB) edge seals make module opening extremely difficult, impeding the separation of functional layers and limiting recyclability.

We address these challenges through two complementary design innovations. First, we replace traditional solid encapsulants with a liquid silicone oil encapsulation, which provides environmental protection while enabling straightforward separation of the solar cell stack and glass cover without heat or chemical treatment. Second, we incorporate sacrificial layers within the PIB edge seal, which disintegrate under mild thermal activation below 80 °C, allowing rapid, low-energy opening of the encapsulated device. Together, these strategies enable complete, non-destructive disassembly of PSC modules while maintaining high stability and performance, verified through damp-heat and thermal cycling tests. The encapsulation can be reopened and reused, allowing multiple device lifecycles and minimizing material waste.

To further enhance end-of-life sustainability, we fabricate PSCs on biodegradable substrates derived entirely from renewable, fossil-free feedstocks. Unlike conventional glass or plastic, these substrates permit environmentally benign disposal or composting once device layers are removed, closing the materials loop. Combined with recyclable encapsulation, this approach enables a fully sustainable device architecture in which both active and passive components are recoverable or degradable.

These design strategies demonstrate that recyclability and high performance can coexist in perovskite photovoltaics. By embedding sustainability principles directly into module architecture through reversible encapsulation, reusable components, and bio-based materials, this work advances PSC technology toward a truly circular photovoltaic economy. The results offer a blueprint for designing next-generation solar modules that not only harvest clean energy but also minimize environmental impact throughout their entire life cycle.

Luminescence-based optical imaging is a powerful, contactless, and non-destructive tool for investigating halide perovskite materials and solar cells across all stages of their development. In this talk, I will present how multimodal photoluminescence techniques enable microscopic, quantitative insights into perovskite stability, optoelectronic properties, and device performance. First, I will examine the response of halide perovskites to external stressors such as humidity and X-ray illumination, highlighting the emergence of self-healing behaviour after irradiation. I will then demonstrate how quantitative photoluminescence imaging links fundamental optoelectronic properties to device-level performance, with particular emphasis on interfacial passivation using organic cations to suppress non-radiative recombination. These methods are also extensible to the characterization of larger devices. We demonstrate this by applying a quantitatively calibrated hyperspectral PL/EL imaging approach to a 64 cm² perovskite mini-module, enabling spatially resolved EQE maps derived from EL measurements. This multimodal method reveals recombination hotspots, transport bottlenecks, and series-resistance variations that drive FF and PCE heterogeneity, highlighting key upscaling losses in interconnected modules. Finally, I will introduce an unsupervised deep-learning framework that overcomes noisy data and long acquisition times of time-resolved fluorescence imaging (TR-FLIM). By combining Noise2Noise training with physics-informed modelling, the method yields high-fidelity lifetime maps from short exposures, reducing sample degradation while enabling accurate extraction of bulk and surface recombination parameters. It is therefore suitable to performe operando experiment of fragile materials. 

Due to their favorable band gap, photovoltaic devices based on inorganic perovskites, such as CsPbI₃, are of great interest. Most photovoltaic applications require the deposition of an active perovskite layer several hundred nanometres thick on structured indium tin oxide (ITO) layers. However, depositing CsPbI₃ on structured ITO often causes a phase transition from perovskite, which is localised at the border between conductive ITO and glass, to the non-perovskite δ-phase. In our study, we investigate the impact of substrate topography on the high-temperature stability of the perovskite phase.

By comparing ITO structuring methods (i.e. laser structuring and chemical etching), we demonstrate that perovskite degradation consistently begins at the ITO/glass border on laser-patterned substrates. Scanning electron microscopy, electron backscatter diffraction and confocal microscopy reveal significant local differences at the ITO/glass border for chemically treated and laser-ablated ITO. These differences were recreated using laboratory patterning experiments, showing that CsPbI₃ strictly degrades on the lab-patterned ITO in line with the trend previously observed for commercial patterned ITO substrates. Disentangling the structural and topographical differences at the ITO/glass interface showed that the local ITO structure and grain size do not affect the perovskite layer. However, steep surface steps of at least 50–100 nm in height, particularly at the edges of laser microcraters, are sufficient to trigger the localised formation of the δ phase at the β-CsPbI₃ formation temperature. This effect sporadically occurs on mechanically damaged substrates; however, it disappears at micrometer-sized scratches, regardless of slope steepness. Thus, it manifests when the topographical detail is comparable to the perovskite grain size.

Rather than offering a device-level optimization strategy, our study provides a visual and mechanistic understanding of how substrate geometry influences phase instability during film growth. This knowledge paves the way for substrate design strategies that suppress phase instabilities arising during the fabrication of perovskite-based inorganic optoelectronic devices.

Perovskite solar cells (PSCs) have recently reached power conversion efficiencies above 26%, but their long-term stability under realistic operation is still a major bottleneck for commercialization. Under outdoor conditions, devices repeatedly switch between light and dark. During these phases, partial recovery can accompany degradation, yet the physical mechanisms, especially in the dark, and in their interplay with light-induced processes, remain poorly understood [1,2].

In this work, we analyze aging data from different indoor ISOS tests using physics-based device simulations to study recovery mechanisms in PSCs under dark and light conditions, with a focus on key stability challenges in metal halide perovskites. A one-dimensional optoelectronic model couples optical transfer-matrix calculations with drift-diffusion transport. This is used to simulate JV characteristics close to experimental ones via a genetic algorithm that generates ensembles of parameter sets consistent with the initial device performance. Starting from these ensembles, we simulate recovery and degradation pathways by systematically varying material properties, such as carrier mobilities and defect densities, and track their signatures in open-circuit voltage, short-circuit current and fill factor.

The evolution of these electrical parameters is analyzed in a novel correlation-space representation, which enables a direct comparison between experimental trajectories and simulated mechanisms [3]. Applying this framework to recovery intervals identified in dark-light cycling data and to protocols under continuous illumination, we obtain insights on reversible and irreversible processes in the devices. Preliminary results highlight the role of deep defects in the perovskite absorber and of doping in the transport layers in leading both degradation and recovery. Some of the explored mechanisms act in a reversible way, meaning that the same underlying change can drive degradation in one phase and partial recovery in another. The proposed methodology offers a physics-based approach to screen feasible mechanisms behind signatures of instability and to guide experimental efforts aimed at improving the operational stability of PSCs.