Metal halide perovskite solar cells have become a viable option for future renewable energy. Record single- and tandem-junction all-perovskite solar cells already provide power efficiencies of 28% and 30%, respectively. By monolithically stacking multiple perovskite sub cells with complementary bandgaps and using recombination junctions designed to provide near-zero electrical and optical losses, it is possible to fabricate monolithic multi-junction configurations with high power conversion efficiencies [1]. These require highly efficient and stable perovskite sub-cells with bandgaps over a wide spectral range. Especially for narrow- and wide-bandgap perovskites several challenges still remain in reducing the energy losses and enhancing the stability. Within this general framework I will focus on recent results.

For narrow-bandgap (1.25 eV) tin-lead perovskites we developed novel insulating-passivating interfaces for the electron and hole transport layers that enable high-photovoltage in single- and double-junction solar cells. To create an optimal bandgap (1.34 eV) absorber for single-junction solar cells mixed-metal mixed-halide perovskite have been developed that do not show light-induced halide segregation during prolonged illumination and provide a power conversion efficiency of 19% [1],  among the highest for perovskites in the 1.3 − 1.4 eV range. For tandem-cells an efficient 1.77 eV bandgap perovskite has been developed. It will be shown how common bulk or surface passivating agents disturb the perovskite stoichiometry in such a way that the performance is reduced. Interestingly, compensating for the deficiency or excess created by the passivation and restoring the desired stoichiometry of the precursor fully recovers the device performance [2]. For triple-junction solar cells, 2.05 eV bandgap perovskites are needed.  By carefully adjusting passivating strategies that prevent early halide segregation, we have been to reach over 10% efficiency at improved stability. For quadruple-junction cells, 2.3 eV perovskite solar cells are needed for which a dual-passivation strategy has been found for bulk and surface passivation, which, combined with a ternary fullerene blend electron transport layer, increase the open-circuit to 1.60 V [3]. Finally we tune absorption onsets to the 2.3–3.0 eV range with mixed Br-Cl perovskites and reveal how chloride incorporation shapes structural, optoelectronic, and photovoltaic properties.

Perovskite optoelectronic devices, including solar cells (PSCs) and light-emitting diodes (PeLEDs), have attracted significant attention owing to their exceptional optoelectronic properties and solution-process compatibility. However, the widespread use of conventional indium tin oxide (ITO) transparent conductive electrodes (TCEs) remains limited by their susceptibility to chemical degradation under acidic processing environments and concerns regarding material cost and sustainability.[1] Here, we develop sputtered nitrogen-doped SnO₂ (NTO) transparent electrodes as chemically robust, indium-free, and scalable alternatives to ITO for high-performance perovskite optoelectronics.[1,2] By optimizing nitrogen incorporation during magnetron sputtering, NTO electrodes exhibit low sheet resistance (≈37–39 Ω sq^-1), high visible transmittance (up to 86.17%), ultrasmooth surface morphology (root mean square roughness ≈1.2 nm), and favorable energy-level alignment with adjacent charge-transport layers. Nitrogen doping enhances electrical conductivity and chemical durability through the formation of Sn–N bonds and oxygen vacancies, while simultaneously improving interfacial homogeneity and charge extraction/injection characteristics. When integrated into chemical-bath-deposited SnO₂-based PSCs, the optimized NTO electrode enables a power conversion efficiency of 20.43% and retains 93.30% of its initial performance after 3,000 h without encapsulation. Furthermore, NTO-based green-emitting PeLEDs achieve a peak external quantum efficiency of 20.82%, a luminance of 5,323.8 cd m^-2, and more than twice the operational lifetime of comparable ITO-based devices.[2] These results demonstrate that NTO serves as a versatile transparent electrode platform capable of simultaneously enhancing efficiency, interfacial stability, and long-term durability across both photovoltaic and light-emitting perovskite technologies, providing a promising pathway toward sustainable next-generation optoelectronic devices.

Metal halide perovskites have emerged as a highly promising class of semiconductors for optoelectronic applications due to their exceptional light absorption, tunable emission, and efficient charge transport. These cost-effective materials have demonstrated an unprecedented rise in solar power conversion efficiency, reaching 28% within a decade, outpacing conventional silicon photovoltaics. However, fundamental insights into their intrinsic photophysical properties remain incomplete, yet are crucial for further performance enhancements. Additionally, while the impressive efficiency of novel perovskite materials is often emphasized, their long-term stability is equally vital for practical implementation.^[1]

I will present the development of perovskite systems with diverse compositions, structures, and morphologies using various synthesis strategies. By employing advanced spectroscopic techniques, we elucidate the interplay between crystalline structure and charge carrier dynamics that dictate their optoelectronic performance.^[2,3] Additionally, photoluminescence (PL) microscopy imaging is being exploited correlating materials’ photochemistry and intrinsic defects to optoelectronic device performance, providing direct insight into their function in real-world applications.^[4,5] I will demonstrate how chemical micro-engineering can optimize perovskite stability and functionality, with a focus on improving X-ray detection performance.^[6,7] Finally, I will present strategies for fabricating high-quality photoactive layers, including controlled film deposition, as critical components for next-generation stable optoelectronics.

Recent developments in aromatic self-assembled monolayers (SAMs) have improved energy-level alignment and strengthened π–π stacking interactions, thereby facilitating more efficient charge transport in inverted perovskite solar cells (PSCs). However, a significant limitation remains, i.e., the relatively large steric footprint of aromatic SAM molecules often results in loose molecular packing and an increased likelihood of nanoscale void formation. To address this challenge, we employ a co-adsorption strategy by incorporating a smaller aryl phosphonic acid into the aromatic SAM. Owing to its reduced size and compatible anchoring group, the introduced arylphosphonic acid effectively occupies the intermolecular voids between bulky aromatic units, resulting in a more compact, homogeneous, and void-free monolayer. The co-assembled structure preserves the favourable electronic properties of the aromatic SAM while enhancing surface coverage and interfacial uniformity, resulting in improved energy level alignment, as evidenced by AFM measurements, enhanced perovskite film growth observed from SEM analysis, and suppressed trap-assisted non-radiative recombination, confirmed by photoluminescence quantum yield measurements. Consequently, PSCs based on this co-adsorbed layer achieve a power conversion efficiency of 24.8%, along with a Voc of 1189mV, FF of 85% and Jsc of 24.5mAcm^-2 on a 0.096 cm² area device. Furthermore, the fabricated PSCs with this co-adsorbed SAM exhibit high operational stability, demonstrating that this strategy offers a versatile approach for optimizing aromatic SAMs interfaces for high-performance and stable inverted PSCs.

Keywords: Interface Engineering, Inverted Perovskite Solar Cells, Non-radiative Recombination, Self-Assembled Monolayers, Co-adsorption Strategy

Light emission in the blue, violet, and UV portion of the spectrum is of crucial importance: blue devices are required for emissive devices, while violet and UV emission plays a key role in manufacturing, sensing, photochemistry, and sanitization and purification. Despite these needs, however, perovskite performance at these wavelengths has lagged behind red and green emitters. In this talk, we will discuss our efforts to achieve efficient photoluminescence and electroluminescence across these wavelength ranges. We will demonstrate the positive role of dopant addition to perovskite materials and highlight how careful control of fabrication conditions allows for more efficient emission. We will show how these innovations translate to devices, and highlight ongoing challenges with emissive efficiency and stability. Finally, we will highlight chemical efforts towards more effective emission in the UV, and how these techniques can be combined to open new optoelectronic opportunities towards effective devices for medical, sterilization, and manufacturing opportunities. 

The commercial deployment of metal halide perovskite photovoltaics hinges on bridging the gap between small-scale laboratory efficiencies and long-term operational stability at an industrial scale. Physical and chemical interfaces within these device architectures represent critical bottlenecks, governing non-radiative recombination, ion migration, and energetic misalignment. This talk presents a comprehensive approach to mastering these boundaries by controlling the buried heterojunction, understanding long-term surface evolution, and deploying multimodal strategies for scalable optoelectronic applications. First, we address the buried interface by introducing a multifunctional polymer matrix (sodium hyaluronate) to disperse SnO2 nanoparticles. This approach yields highly uniform, strain-relaxed perovskite films with eliminated oxygen vacancies, achieving a champion power conversion efficiency (PCE) of 25.11% and excellent ambient stability^[1]. Second, we explore the dynamic nature of 2D/3D surface heterojunctions under long-term operation. We systematically trace the evolution of charge carrier dynamics as these interfaces age, demonstrating that controlled phase changes and the emergence of PbI2 crystals can naturally optimize interfacial band alignment, boosting the open-circuit voltage from 1.14 V to 1.18 V^[2]. Finally, we translate these fundamental interface insights into functional, scalable technologies. By combining transfer matrix optical modeling with targeted molecular passivation (using 3-trifluoromethyl-1H-1,2,4-triazole), we overcome the transparency-efficiency trade-off in semi-transparent perovskite solar cells for building-integrated photovoltaics and indoor electronics. This framework achieves a record indoor PCE of 22.41% under 1000 lux illumination and successfully scales to a 30 x 30 cm2 semi-transparent module ^[3]. Together, these interlinked interfacial strategies provide a clear, industrially compatible roadmap toward highly stable, next-generation perovskite technologies.

Metal halide perovskite solar cells have achieved power conversion efficiencies (PCEs) above 27% for single junctions and approximately 35% for perovskite–silicon tandems. Industrial deployment, however, requires translating these results into large-area modules that combine high efficiency, spatial uniformity, and long-term reliability. This talk presents molecular engineering of the perovskite absorber within a fully industry-compatible device stack as a route from lab to fab, spanning scalable deposition and interconnection, encapsulation, accelerated testing, and multi-year field validation.

We frame the cell-to-module efficiency gap as a property-distribution problem: a sub-centimetre cell averages local variations in film quality, whereas a series-interconnected module is constrained by its least-performing sub-cell. Controlling spatial optoelectronic heterogeneity, not merely average film quality, is therefore essential for upscaling. To this end, we introduce a multifunctional crystallization-directing molecular additive into the perovskite precursor ink. All devices employ an identical industrial stack — linear-sputtered ITO front electrode, sputtered NiO_x hole transport layer, and evaporated passivation and electron transport layers — with only the absorber deposition adapted to substrate area: blade coating up to 100 cm² and slot-die coating at ~800 cm². This design isolates absorber chemistry as the scaling lever. The additive produces a large-grained, phase-pure absorber and improves optoelectronic uniformity, raising active-area PCE from 22.0% to 23.0% (0.125 cm² cells), 19.0% to 21.3% (3.9 cm² devices), 17.8% to 21.2% (15.5 cm² mini-modules), and 13.7% to 19.0% (100 cm² monolithic modules). The gain widens monotonically with area, from +1.0 to +5.3 percentage points, reducing the absolute upscaling loss by a factor of 2.1. Multi-scale characterization corroborates this improvement: large-area photoluminescence imaging reveals reduced property dispersion, correlative electron microscopy–cathodoluminescence shows recrystallized large grains and suppressed secondary PbI₂, and two-dimensional ¹H–¹H spin-diffusion NMR confirms that the additive–lattice interaction persists across the relevant length scales. Encapsulated mini-modules retain ~90% of initial efficiency after 1000 h damp heat (85 °C, 85% RH), 92% after 500 thermal cycles (−40 °C to 85 °C), and 85.2% after 159 days outdoors in Nicosia, Cyprus.

At fab scale, the identical stack transfers to ~800 cm² substrates with the additive-engineered absorber deposited by slot-die coating. Modules with metal top electrodes reach 18.3% PCE, while a soft-sputtered ITO top electrode yields semi-transparent modules with superior long-term stability: a 781 cm² module achieved 15.2% aperture-area efficiency (16.3% active area), and encapsulated modules maintained T₈₈ after one year of outdoor tracking in Crete, Greece. Ongoing optimization targets 18% PCE for the semi-transparent format, which also enables four-terminal perovskite/silicon tandems.

Finally, because accelerated ageing protocols cannot fully capture coupled environmental stressors or predict the service lifetimes required for bankability, we complement indoor testing with extensive outdoor campaigns. The reproducible process and operationally stable formulation enable meaningful comparison of field performance across samples. We report four years of outdoor data across diverse climates, including arid desert and polar deployments, revealing degradation pathways and failure modes not observed under conventional test conditions and providing benchmarks for material and device design.

These results establish molecular-level control of crystallization within an unchanged industrial stack as a chemically tractable, transferable scaling strategy, carrying a single additive concept from 0.125 cm² cells to ~800 cm² modules across two coating methods. The talk will conclude with remaining bottlenecks and the roadmap toward durable, high-performance perovskite modules and tandems for commercial production.

Light management is one of the key strategies for pushing the efficiency of perovskite solar cells. While smoother perovskite surface layers are desirable for improving charge transfer with the overlying charge transport layer, increasing the contact interface area also offers enhanced charge transport.

To address this, we have developed a surface patterning technique for perovskite and its overlying charge transport layer using a picosecond pulsed laser. This contactless, fast and highlty precise patterning technique overcomes the challenges of expensive fabrication processes such as masking and lithography, completing the process in a fraction of a second.

In this work, we report an increased open circuit voltage from 1.06 V to 1.10 V for a comparable thickness. Additionally, by controlling the laser fluence, we demonstrate control over etch depth ranging from 30 to 100 nm across different periodicities. This work opens the possibility of exploring light-matter interactions in halide-perovskites based optoelectronic devices.

Hybrid perovskite/silicon tandem solar cells have demonstrated strong potential to surpass the power conversion efficiency limits of single-junction devices while maintaining low production costs, with power conversion efficiencies reaching up to 34.6%. However, hybrid perovskites are currently not stable enough for large-scale deployment. Photo-induced degradation remains a major obstacle to the use of perovskites in solar cells, affecting their long-term stability. Current photochemical degradation models are still limited, particularly regarding the impact of halide composition and environmental conditions on perovskite stability. Our study aims to address these limitations by proposing a kinetic model investigating mixed-halide triple-cation perovskites, with a focus on the degradation kinetics associated with iodine and formamidinium losses, as well as the production of metallic lead (Pb(0)) under illumination [1].

First, we used X-ray photoelectron spectroscopy (XPS) to monitor the degradation of our perovskite material (FAPbI_1-xBr_x, where FA = formamidinium) induced by white-light exposure. This degradation is characterized by the formation of metallic lead in the zero oxidation state (Pb(0)) [1–3]. We then developed a kinetic model describing the evolution of lead, halide (I, Br), and formamidinium concentrations. To build this model, we assumed that the photodegradation process occurs in two steps. In the first step, the perovskite material degrades into lead iodide with the release of FAI in gaseous form. In the second step, lead iodide further decomposes into metallic lead (Pb(0)) while releasing gaseous I₂. By considering these two steps as first-order chemical reactions, we established differential equations describing the time evolution of Pb, FA, and I concentrations. The results of our model show good agreement with the evolution measured experimentally.

Using atomic force microscopy (AFM) together with our kinetic model [3], we provide insights into the environmental effects on perovskite durability (ultra-high vacuum versus N2 environment), confirming that light-induced degradation occurs in both environments but through distinct mechanisms. In the literature, the absence of a Pb(0) signal in XPS is often associated with improved perovskite stability. However, through local probe microscopy measurements, we demonstrate here that the perovskite material can still degrade without generating a detectable Pb(0) signal in XPS.

Our results also reveal that an increased bromine content (x = 5 to 20%) improves perovskite stability while highlighting distinct degradation pathways between nitrogen (N2) and ultra-high vacuum (UHV) environments. This finding contradicts previous claims of stability under N2 atmosphere. Overall, these results emphasize the importance of understanding degradation processes in order to optimize perovskite materials for future applications.

The hole transport layer (HTL) plays a critical role in charge extraction and operational stability in n–i–p perovskite solar cells (PSCs). Spiro-OMeTAD remains the most widely used HTL; however, its conductivity relies on Li-TFSI and 4-tert-butylpyridine (tBP) additives and a slow oxygen-induced oxidation process that typically requires several days to complete.[1] Moreover, the presence of tBP compromises the thermal and environmental stability of the HTL, limiting both device durability and manufacturing efficiency. Developing charge transport layer engineering strategies that simultaneously accelerate HTL activation and improve stability remains an important challenge.[2-5]

Here, we report a tBP-free HTL engineering strategy by incorporating oleyl amine (OAm) coated nickel oxide nanoparticles (oil-NiO_x NPs) into the Spiro-OMeTAD/Li-TFSI system. The oil-NiO_x NPs promote homogeneous Li-TFSI dispersion and chemically interact with Li-TFSI to generate Ni³⁺ species, which efficiently oxidize Spiro-OMeTAD without prolonged air exposure. As a result, the HTL activation time is dramatically reduced from approximately 72 h to only 3 s, providing a simple and manufacturing-compatible route for rapid device fabrication.

Perovskite solar cells employing the oil-NiO_x NP-engineered HTL exhibit an initial power conversion efficiency (PCE) of 22.05%, which further increases to 24.20% after 72 h, outperforming conventional tBP-containing devices (12.49% initially and 23.52% after oxidation). More importantly, the elimination of tBP substantially improves operational stability, with the optimized devices retaining 94%, 61%, and 80% of their initial efficiency after 800 h under 55% relative humidity, 85 °C thermal stress, and continuous illumination, respectively.

This work demonstrates an effective charge transport layer engineering strategy that enables ultrafast HTL activation while simultaneously improving device efficiency, environmental stability, and processing compatibility. The proposed tBP-free approach provides a scalable pathway toward reliable, high-performance perovskite photovoltaics.