The stability of Sn-Pb perovskite semiconductors thin films remains a major challenge for their integration into efficient and durable photovoltaic devices. In this work, we demonstrate that the incorporation of methylammonium chloride (MACl) in DMSO-free Sn-Pb precursor solutions significantly enhances both the structural and operational stability of Sn-Pb perovskite films and solar cells. MACl-processed films exhibit enhanced crystallinity, environmental stability and photostability, thus tackling the most critical instabilities related to the defect chemistry of tin in tin-based perovskites and halides in lead-based perovskites. We show that Cl- preferentially resides at the Pb0.5Sn0.5I-terminated surface, reducing the formation probability of halide interstitials, preventing I2 loss under illumination and reducing O2 uptake under ambient air exposition. As a result, solar cells incorporating MACl-treated films maintain stable performance under maximum power point tracking for over 900 h. This work highlights the crucial role of interfaces and paves the way for more durable perovskite solar cells.

Perovskite thin film-based laser diodes have emerged as promising candidates for on-chip laser sources. However, despite the successful demonstration of optically pumped lasing, the realization of electrically pumped perovskite laser has proved to be quite challenging. Here, we investigated the optical gain mechanism in polycrystalline perovskite thin film by mapping the spatial distributions of amplified spontaneous emission within the heterogeneous thin film and its spatial correlation with the local electronic properties. We discovered that optical gain within these polycrystalline perovskite thin films occurs primarily at defective sites, where despite the low photoluminescence efficiency demonstrated high optical gain efficiency, lower treshold and long photocarrier lifetime. Our findings highlight the importance of defects in the development of electrically pumped laser diodes.

The presence of excess lead iodide (PbI2) in lead halide perovskites can accelerate solar cell degradation. Under illumination, PbI2 readily undergoes photodecomposition, producing metallic lead (Pb0) that introduces deep trap states and iodine (I2) that destabilizes the bandgap and phase stability, particularly for the alpha phase of FAPbI3. To mitigate these phenomena, we demonstrate a proof-of-concept approach by introducing potassium bromate (KBrO3), an oxidizing agent, between the metal oxide electron transport layer (ETL) and the FAPbI3 perovskite layer. It suppresses the excessive formation and photoinduced decomposition of PbI2 by enhancing the crystallinity of the perovskite layer and passivating the undercoordinated lead with internal oxygen sources. The resulting KBrO3-treated device achieved a power conversion efficiency (PCE) of 24.10% with respect to 21.21% of that of the control sample. Importantly, the operational stability, tested following the ISOS-L-1 protocol, is enhanced with the device maintaining 86% of its initial PCE after 1000 h. This study suggests a new perspective for improving photostability in Pb-based perovskite films.

Mixed I-Br perovskites are promising top absorbers for tandem solar cells due to their tunable band gap and solution processability, yet photoinduced halide segregation-a critical but poorly understood degradation mechanism-hinders their reliability. Here, we demonstrate how the enhancement of the Br- binding energy in the perovskite inhibits I2Br- formation-the key intermediate species driving halide segregation. The incorporation of densely charged cations like Sr2+ in the perovskite strongly localizes halide anions, inhibiting their electron donation to photogenerated I2 and preventing triple halide ion formation, which eventually suppresses halide segregation. Additionally, this also reduces undercoordinated Pb at grain surfaces, suppressing nonradiative recombination. These synergistic effects yield high-performance solar cells with champion efficiencies of 20.18% at 1.77 eV and 19.02% at 1.84 eV, alongside enhanced stability. Our work establishes a design principle to mitigate halide segregation in mixed-halide perovskites, overcoming a major challenge in perovskite optoelectronics.

Vacuum-deposited lead halide perovskite thin films enable solvent-free fabrication, eliminating residual processing solvents that might compromise the long-term stability. Here, we investigate the stability of thermally evaporated mixed-cation compositions FA0.8Cs0.2PbI3 and FA0.8MA0.2PbI3 (FA+ = formamidinium and MA+ = methylammonium) under thermal and light stress. Although from a thermodynamic perspective the phase stability hierarchy is typically described as MA+ < FA+ < Cs+, with Cs-based perovskites expected to be the most stable, both compositions exhibit thermal robustness, retaining their structural, optical, and morphological properties after continuous heating at 85 °C for over 500 h. Under continuous illumination, however, distinct degradation pathways emerge: FA0.8Cs0.2PbI3 shows the largest morphological and optical changes. This is attributed to chemical inhomogeneities caused by CsI-rich segregations during crystallization, which make point defects effective triggers for photodegradation. Film homogeneity improves by partially replacing iodide with bromide. Based on these results, we selected FA0.8MA0.2PbI3 and FA0.8Cs0.2Pb-(I0.8Br0.2)3 for device fabrication and evaluated their operational stability. The resulting perovskite solar cells maintain their performance after four months of outdoor operation and withstand 900 h under continuous sun-equivalent indoor illumination at room temperature. These results demonstrate how a high-quality crystallization process can reveal the potential of MA-containing perovskite formulations for long-lived perovskite photovoltaics.

Photocatalytic nitrogen fixation (PNF) offers a green route to ammonia synthesis under ambient conditions. We present a scalable synthesis of BiOBr/g-C3N4 heterojunctions and identify that the composition with 10 wt% BiOBr achieves similar to 20 & micro;mol g-1 h-1 ammonia production-outperforming pristine materials of the heterojunction. Mechanistic investigations reveal that enhanced activity stems from efficient charge separation, supported by time-resolved spectroscopy showing extended carrier lifetimes. DFT calculations reveal that the catalytically active (010) surface of BiOBr exhibits favorable band alignment with g-C3N4 and enables downhill electron transfer to the N2/NH3 redox level. Crucially, this surface hosts localized electron polarons, which act as reactive sites for nitrogen reduction. In contrast, the (001) surface lacks such features, explaining the reduced performance at higher BiOBr loadings. These findings establish a direct link among surface structure, charge dynamics, and catalytic functions, offering design principles for next-generation photocatalysts for sustainable ammonia production.

We report the structural and optoelectronic properties of lead-free CsGeI3 and CsGeBr3 perovskites, unveiling the critical role of local symmetry distortions in defining their emission properties. CsGeBr3 exhibits broad photoluminescence from self-trapped excitons, due to local octahedral distortion and a large distribution of the average bond lengths. On the contrary, by using temperature-dependent pair distribution function analysis and hybrid-functional molecular dynamics simulations, we demonstrate that CsGeI3 adopts a monoclinic local structure responsible for its narrow near-infrared (NIR) emission (∼745 nm, FWHM ≈ 110 meV at room temperature), the narrowest reported for Ge-based perovskites and in line with tin iodide perovskites. Notably, the high level of structural order also supports the achievement of amplified spontaneous emission (ASE) at room temperature with an exceptionally low threshold (75 μJ/cm2), positioning it as a promising candidate for lead-free NIR light-emitting and laser applications.

Edible electronics offer a unique platform for developing devices made entirely from food-based materials that can be safely digested or excreted without environmental concerns. Yet, identifying semiconductors that are both food-based and capable of supporting efficient charge transport remains a challenge. In this work, we show that this hurdle can be overcome by applying structure-property insights developed in organic electronics to natural compounds, revealing how a material previously discarded for electronic applications and largely present in vegetables, β-carotene, can be tuned into a viable semiconductor. Beyond its implications for edible electronics, this approach also highlights the broader potential of renewable, nature-derived materials as building blocks for sustainable technologies.

The interfaces between the charge extraction layers and the perovskite layer are critical in defining the performance and stability of wide-bandgap (WBG) perovskite solar cells (PSCs). They govern multiple critical factors affecting the operation of photovoltaic devices such as the energetics of the contact, and the crystallization process of the thin film, thus its structural and electronic quality. Self-assembled monolayers (SAMs) have emerged as promising candidates as hole-selective materials for inverted PSCs, thanks to the flexibility provided by the large library of their functional groups. Herein, we outline a molecular hybridization strategy through the incorporation of the histamine molecule into the [4-(3,6-dimethyl-9H-carbazol-9yl)butyl]phosphonic acid (Me-4PACz), which is one of the most common hole extracting layers. Playing with intermolecular strong and weak interactions, we can contextually act on multiple processes. The proton transfer from the phosphonic acid group of the Me-4PACz to the ethylamine functional group of histamine enables the design of the interface dipole to facilitate hole extraction and minimize recombination losses. Then, the protonated amines balance the nucleation of halide components and stabilize the halide ions in the perovskite, avoiding their migration. Thus, three-dimensional nanovoids and tensile stress at the bottom surface were reduced, stabilizing the buried interface. Finally, the pi-pi interactions between the imidazole moiety and Me-4PACz improve the molecular assembling of the SAM, reducing disorder at the interfacial contact. The general impact of these results has been tested on PSCs based on lead mix-halide perovskites with two different bandgaps. The inverted WBG PSCs with 1.77 eV bandgap present a power conversion efficiency (PCE) of 20.34%, and maintain 95.5% of the initial PCE after 1000 hours of continuous illumination. The highly challenging WBG PSCs with 1.83 eV bandgap deliver a PCE of 18.99% with a Voc as high as 1.364 V-ranking among the highest reported PCEs and Voc values for such large bandgap.

Coevaporation of formamidinium tin triiodide (FASnI3) precursors, without any additives or reducing agents, leads to the growth of a highly crystalline thin films which show a bandgap around 1.31 eV, closely matching the theoretical value predicted from the ideal single crystal structure of FASnI3. The polycrystalline thin film presents a lower tendency toward Sn2+ to Sn4+ oxidation and highly reduced tendency toward self-doping, demonstrating, overall, an improved resistance to defects formation. These findings suggest solvent-free coevaporation processes as a promising route for high quality Sn-based perovskite polycrystalline thin films.

Self-assembled monolayers (SAMs) have revolutionized the fabrication of lead-based perovskite solar cells, but they still remain underexplored in tin perovskite systems. To date, PEDOT remains the most effective hole-selective layer in tin perovskite solar cells (TPSCs), yet it presents challenges for both performance and stability. MeO-2PACz, the only SAM reported for tin perovskites consistently underperforms when compared to PEDOT. In this work, it is identified that MeO-2PACz's limitations stem from excessively strong interactions with the perovskite surface and poor lattice matching, which leads to inferior interface quality. To address these issues, a novel SAM-forming molecule called Th-2EPT is designed, synthesized, and characterized. Density functional theory (DFT) is used to evaluate coordination strength and lattice compatibility, complemented by electro-optical characterisation techniques that show significantly reduced interfacial recombination and improve material crystallinity in Th-2EPT/Perovskite films. With Th-2EPT, the first SAM-based tin perovskite solar cells that outperform PEDOT-based devices, delivering a power conversion efficiency (PCE) of 8.2% with a DMSO-free solvent system, are demonstrated.

Tin-halide perovskites are emerging as exceptional materials for near-infrared light-emitting diodes (NIR-LEDs). However, their extreme oxygen sensitivity remains a significant obstacle to practical applications. This work presents a facile yet effective strategy to overcome this limitation by designing self-encapsulated tin-halide perovskite films. Incorporating a rational molecule, 4,4'-diaminodiphenyl sulfone, into precursors, it forms isolated tin-iodide perovskite particles that are encapsulated in situ, achieving outstanding air stability. The resulting films show high crystallinity, reduced trap density, and mitigated p-doping density, boosting radiative charge recombination to reach an impressive photoluminescence quantum yield approaching 50%. Leveraging these advancements, the resulting NIR-LEDs demonstrate a record-breaking peak external quantum efficiency of 12.4%, accompanied by a substantial improvement in operational lifetime. Notably, for the first time, we demonstrated a functional tin-iodide perovskite-based device in ambient air. This work provides a robust pathway for realizing high-performance and stable tin-halide perovskite-based optoelectronic devices, addressing critical challenges for their widespread application.

The tunability of hybrid organic-inorganic metal halides through targeted chemical design is one of their most attractive features, enabling fine control over physical properties for optoelectronic applications. In chiral systems, where chirality is introduced via organic amines, this tunability is often limited by the scarcity of suitable chiral cations. In this study, we report a family of 1D lead- and tin-based chiral hybrid halides incorporating a tailor-made cation bearing both amino and hydroxyl functional groups. This chiral ligand enables the synthesis of enantiopure (S/R-AMOL)-SnI3 and (S/R-AMOL)-PbI3, where S/R-AMOL stands for (2S,2'S)-1,1'-azanediylbis-(butan-2-ol) or (2R,2'R)-1,1'-azanediylbis-(butan-2-ol). These compounds exhibit distinctive structural arrangements and bonding interactions, demonstrating effective chirality transfer through chiral centers bearing hydroxyl groups. Remarkably, substantial differences in the electronic structure and chiroptical properties are observed between the Sn and Pb analogues, including variations in emission characteristics, exciton binding energy, and orbital contributions to the electronic structure.

Two-dimensional (2D) van der Waals (vdW) materials have garnered significant interest due to their unique properties, including strong light-matter interactions and enhanced excitonic effects [1]. Among these, layered vdW metal phosphorus trichalcogenides $(\text{MPX}_{3})$ represent a fascinating class of perovskites, exhibiting peculiar magnetic, optoelectronic, and optical properties, with bandgap ranging from 1.3 to 3.5 eV [2], [3]. HgPSe3, is a vdW semiconductor with an optical gap near 2 eV at room temperature, characterized by high sensitivity to X-rays, effective responsivity in the visible spectrum and fast response times, positioning it as a promising candidate for fast broadband light detection [4], [5]. However, while its static optical properties are well studied, the material's non-equilibrium optical behavior remains unexplored.

Transparent conductive oxides (TCOs)-foundation of perovskite solar cells (PSCs)-have long been assumed to be stable, and thus their impact on device longevity is frequently overlooked. Herein, we unveil that fluorine doped tin oxide (FTO) suffers from instability under operational stress, exacerbating PSC stability issue. To address this issue, we propose a universal interface engineering strategy employing a scalable thermal evaporation followed by natural oxidation to form an atomically bonded yttrium oxide (Y2O3) to strengthen structural stability of FTO. Evaporated yttrium effectively anchors a portion of lattice oxygen within FTO, preventing elemental dissociation. Moreover, the formed Y2O3 featured conformal deposition on rough FTO increases the interfacial adhesion energy, establishing a robust barrier against ion diffusion and carrier nonradiative recombination loss. This approach fortifies the structural integrity of the PSC, leading to dramatically improved operational stability. Unencapsulated devices exhibit negligible performance loss after 1,200 h of continuous illumination. Notably, we achieve power conversion efficiencies of 26.48% (certified at 26.12%) in regular (n-i-p) architectures, 26.34% in inverted (p-i-n) configurations, and 28.47% in tandem structures-among one of the highest reported in their respective categories-underscoring its strong generality and potential for commercialization.

Chiral metal halides are promising materials for nonlinear optics and spin-selective devices. Typically, chirality is introduced via large chiral organic cations, leading to low-dimensional structures and limitations in charge transport. Here, we design a family of chiral metal halides based on the relatively small ditopic R/S-3-aminoquinuclidine (3-AQ) cation, forming an (R/S-3AQ)-Pb2Br6 structure closely related to the 3D corner-sharing octahedral network of perovskites. The resulting material exhibits a direct bandgap, isotropic band structure, and fully 3D photoexcitation. Circular dichroism confirms a chiral anisotropy factor consistent with theoretical predictions. Moreover, the material displays a Rashba effect in the conduction band, which is attributed to spin-orbit coupling and the lack of inversion symmetry. Offering rich chemical tunability and efficient 3D charge transport, this new class of chiral semiconductors provides a promising platform for advancing nonlinear optoelectronic and spintronic devices.

Two-dimensional (2D) perovskites are attracting renewed interest for coherent emission. While excellent results have been achieved with tin-based materials, the real applicability of lead perovskites remains controversial due to limited reproducibility. Critically, there is no fundamental explanation so far to provide an educated prediction about their lasing properties. In this work, we compare the 2D perovskites PEA2PbI4, PEA2SnI4, and their mixed compositions. Photophysical characterization and solid-state nuclear magnetic resonance (ssNMR) spectroscopy reveal that molecular motions of the organic cation and local lattice disorder induced by metal cation mixing critically impact the amplified spontaneous emission (ASE) properties of the material. We show that ASE can be achieved for both perovskites at 78 K employing short pump pulse width (fs) and near-band gap excitation. However, stable operation at room temperature is achieved only in PEA2SnI4, thanks to the lower Auger recombination rate, its peculiar lengthening of the excited state lifetime at higher temperatures and lower impact of trap-mediated recombination compared to PEA2PbI4. Our work highlights the importance of defect control and crystal engineering strategies to enhance the structural rigidity and improve the optoelectronic properties of this class of soft semiconductors.

The role of A-site cations (MA+, FA+, Cs+) in the defect chemistry of metal halide semiconductor is well-studied in lead halide perovskites; here we investigate it in the less explored tin perovskites.