Achieving high-efficiency, stable perovskite solar cells (PSCs) requires simultaneous control of film defects and buried interfaces. Here, we report a codeposition strategy using rationally designed 4PACz oligomers. Featuring multidirectional phosphate groups, these oligomers self-assemble to tune the substrate work function, facilitate charge transport, and guide crystallization while passivating defects. Specifically, tri-4PACz achieves an optimal balance between solubility and defect suppression. Consequently, tri-4PACz-based PSCs deliver efficiencies of 26.2% (0.098 cm2) and 22.2% (69.5 cm2 modules). Unencapsulated devices retain 98.7% of initial efficiency after 1000 h of illumination and 96.6% after 500 h at 85 degrees C. This strategy effectively resolves the trade-off between structural control and defect passivation, paving the way for high-performance, stable PSCs.

Narrow-bandgap tin and mixed tin-lead halide perovskites are attracting growing interest for optoelectronic applications, yet the difficult-to-control crystallization process has hindered their development. Although additive engineering has effectively improved film formation, the fundamental origins of their distinct crystallization behavior remain less explored. Here, through direct comparison with Pb counterparts, we investigate the pre-crystallization stages of Sn-based perovskite precursor solutions through complementary structural characterizations. We show that Sn precursors are intrinsically more reactive and sensitive to their chemical environment, exhibiting poorer colloidal stability compared to Pb and a strong inherent tendency to agglomerate. These findings explain their narrower processing window, where small variations in solution chemistry strongly affect nucleation and crystallization dynamics. To fabricate high-quality tin-based perovskite through solution methods, we highlight the importance of controlling the often-overlooked pre-crystallization stages, though, for example, rational solvent and additive designs. Overall, we provide fundamental insights into precursor solution chemistry and establish pre-crystallization engineering as a key strategy for overcoming long-standing limitations in thin-film fabrication, particularly in light of the field's rapid progression toward large-scale, sustainable, and solvent-conscious manufacturing.

Controlling reaction pathways in solids is critical for scalable semiconductor fabrication, yet remains fundamentally challenging in solution-processed systems due to constrained mass transport and diffusion-limited conversion. In perovskite photovoltaics, the widely adopted sequential two-step deposition method is particularly limited by dense PbI2 precursor layers, which impede ion diffusion and lead to incomplete conversion and defect formation. Here we report a photonic strategy to spatially regulate solid-state reaction pathways by engineering micro- and nanoscale channels within PbI2 layers. Laser-induced structures act as deterministic diffusion pathways, enabling controlled ion transport and spatially guided infiltration of organic salts, thereby transforming a diffusion-limited process into a spatially coordinated reaction. Mechanistic investigations reveal that photonic structuring redistributes the local electronic environment and lowers the activation barrier for phase transformation, resulting in accelerated conversion, enhanced crystallinity, and reduced defect density. The resulting perovskite films exhibit improved carrier dynamics. Perovskite solar modules with an aperture area of 22.95  cm2 achieve a record power conversion efficiency of 22.83%, retaining over 90% of their initial performance after 1,500 h under maximum power point tracking. This work establishes photonic control of reaction pathways as a general framework for controlled solid-state transformations.

Tin-lead (Sn-Pb) perovskites have quickly emerged as essential absorbers for narrow-bandgap (NBG) perovskite solar cells (PSCs). However, their development is severely constrained by interfacial energy-level misalignment and chemical instability at the buried interface. This mismatch induces charge extraction barriers, while the rapid oxidation of Sn2 + creates deep trap states and detrimental p-type self-doping. Here, we propose novel redox-active self-assembled monolayers (SAMs) as functional hole-transport layers (HTLs) using ferrocene (FC) derivatives, ferrocene acetic acid (FCAA) and ferrocene carboxylic acid (FCCA), showing better interfacial energetics and eliminating chemical defects via redox mediation. We found that the energy levels of FC-based SAMs align more closely with the Sn-Pb perovskite, promoting efficient hole extraction. Moreover, the reversible FC/FC+ redox process establishes a dynamic cycle, effectively suppressing the undesired oxygen- and light-inducing metallic Pb0 and oxidized Sn4+. FCAA, with a longer alkyl chain that enables stronger electron-donating and redox properties, shows superior to FCCA, achieving a champion power conversion efficiency (PCE) of 23.8%, and retains 95.8% after 2000 hours of storage with significantly inhibited oxidized Sn species. This study proposes a novel functional HTL for Sn-Pb PSCs, providing a promising way for high-performance and stable all-perovskite tandem photovoltaics.

Identifying real-world degradation modes in perovskite solar cells (PSCs) and reproducing them through accelerated aging tests are accomplishments that remain elusive, and this limits progress toward commercialization. Here, we identify three coexisting, spatially non-uniform degradation modes in PSCs following 20 months of outdoor operation: copper corrosion, edge patterns, and phase segregation. By varying light intensity (1 and 2.3 suns) and electrical bias (at the maximum power point [MPP] or open-circuit [OC] conditions) as key stressors, we reproduce and accelerate all three mechanisms. Furthermore, we demonstrate how the interplay of stressors can alter the manifestation of each degradation mode. Among them, phase segregation is the most spatially dominant mode outdoors, and it results in irreversible, micrometer-scale domains. Nevertheless, external stimuli induce optoelectronic changes in these domains that we associate with the metastability observed outdoors. This work links real-world degradation modes to accelerated aging tests, reveals their spatial signatures, and points toward mechanism-targeted acceleration.

Tin (Sn)-based perovskites are promising materials for perovskite-based light-emitting diodes (PeLEDs) that avoid toxic lead. However, the performance of Sn-based PeLEDs lags behind that of their lead analogues due to uncontrolled crystallization, the susceptibility of Sn(II) to oxidation, and high defect densities. In this study, ammonium thiocyanate (NH4SCN) is used as an additive in DMSO-free perovskite precursor solution to afford Sn-based perovskites that are evaluated in PeLEDs. NH(4)SCNmodulates the crystallization process in the solution phase to improve the morphology and crystallinity of the resulting 2D perovskite films and inhibits the oxidation of Sn(II) to Sn(IV), a problem observed in DMSO. Transient terahertz spectroscopy reveals that NH4SCN-based perovskite films have a higher free carrier density compared to the control films, indicative of reduced defect density. Consequently, pure-red Sn-based PeLEDs with an emissive peak of 629 nm achieve an external quantum efficiency of approximate to 1.4%, with an operating half-life of >11 min. These findings provide valuable insights into the preparation of lead-free perovskite materials avoiding DMSO for application in optoelectronic devices.

Two-step-processed (TSP) inverted p-i-n perovskite solar cells (PSCs) have demonstrated significant promise in tandem applications. However, the power conversion efficiency (PCE) of TSP p-i-n PSCs rarely exceeds 24%. Here, we demonstrate that TSP perovskite films exhibit a vertically gradient distribution of residual PbI2 clusters, which form Schottky heterojunctions with the perovskite, leading to substantial interfacial energy-level mismatches within NiOx-based TSP p-i-n PSCs. These limitations were effectively addressed via a vertical interfacial engineering enabled by dual-interface modification incorporating tin trifluoromethanesulfonate (Sn(OTF)2) and 4-Fluorophenylethylamine chloride (F-PEA) at the NiOx/perovskite and perovskite/C60 interfaces, respectively. The functional Sn(OTF)2 not only enhances the conductivity of NiOx films but also suppresses ion migration, while inducing the formation of a Pb-Sn mixed perovskite interlayer that precisely regulates the energy level at the NiOx/perovskite interface. Complementally, F-PEA post-treatment effectively converts surface residual PbI2 clusters into a 2D perovskite capping layer, which simultaneously passivates surface defects and enhances energy-level alignment at the perovskite/C60 interface. Consequently, the optimized NiOx-based TSP p-i-n PSCs achieve a notable PCE of 25.6% with superior operational stability. This study elucidates the underlying mechanisms limiting the efficiency of TSP p-i-n PSCs, while establishing design principles for these devices targeting 26% efficiency.

Tin perovskites are emerging as a sustainable alternative to lead-based photovoltaics, yet their efficiency remains limited by energy-level mismatch and intrinsic instability from tin oxidation. Progress is further hindered by inconsistent electrical behavior, obscuring the true bottlenecks of device performance. Here, we deliver a comprehensive, layer-resolved analysis of FASnI3 solar cells, combining Kelvin probe and photoelectron yield spectroscopy to directly map the band structure and quantify interfacial losses. We reveal that the commonly overlooked Bathocuproine buffer layer plays a decisive role in boosting open-circuit voltage by forming a hybrid energy level with silver, enabling efficient electron extraction.Using time-resolved surface photovoltage, we uncover the ultrafast charge-transfer dynamics governing device operation. These insights expose a critical limitation in the conventional p-p-n, where severe recombination at the perovskite and hole transport interface suppresses performance. A transition to an n-p-p configuration significantly enhances charge extraction and minimizes recombination losses.By integrating these findings into a predictive digital twin, we establish a clear, experimentally validated roadmap toward tin perovskite solar cells exceeding 25% efficiency. This work provides both fundamental understanding and actionable design rules, accelerating the development of high-performance, lead-free photovoltaics.

Self-assembled monolayers (SAMs) have emerged as pivotal components for achieving high-performance perovskite solar cells (PSCs). However, most high-efficiency PSCs employing SAMs utilize Pb-based wide-bandgap (WBG) perovskites, whereas their application in tandem-compatible Pb-Sn mixed narrow-bandgap (NBG) perovskites remains scarcely documented. Herein, high-performance PSCs with Cs-based inorganic Pb-Sn absorbers are fabricated through dipole engineering via co-assembling 4-[(4-aminophenyl)diazenyl]benzenesulfonic acid (4-ASA) with Me-4PACz on NiOx. We demonstrated that 4-ASA induces intermolecular interactions with Me-4-PACz, inhibiting SAM aggregation and micelle formation. This enables the formation of co-SAMs with oriented dipole moments directed from NiOx to the perovskite, thereby effectively optimizing the energy-level alignment at the buried interface. Moreover, the co-SAMs interlayer exhibits a superior hydrophilic surface, serving as an ideal nucleation template for perovskite deposition, contributing to perovskite films with increased grain boundary groove (GBG) angles, suppressed interfacial Sn2+ oxidation, and mitigated residual tensile stress. As a result, the NBG Pb-Sn-based inorganic PSCs achieve a scanned power conversion efficiency (PCE) of 17.82% with outstanding ultraviolet irradiation and operational stability. Furthermore, by integrating NBG (1.36 eV, CsPb0.6Sn0.4I3) and WBG (1.74 eV, CsPb0.7Sn0.3IBr2) subcells, we demonstrate the first four-terminal (4 T) perovskite tandem device in which both subcells are based on Cs-based Pb-Sn mixed inorganic absorbers, achieving a total scanned PCE of 20.36%. Self-assembled monolayers can improve perovskite solar cells, but their use in lead and tin devices for tandem cells is limited. Zhang et al. designed a mixed layer that improved interfaces and crystal growth, producing stable cells and a tandem efficiency of 20.36%.

Perovskite solar cells (PSCs) have demonstrated remarkable potential for photovoltaics, achieving power conversion efficiencies over 27%. However, their commercialization is still hindered by insufficient operational stability under realistic working conditions, including temperature fluctuations, humidity, and continuous illumination. Consolidated experimental evidence indicates that defects in the perovskite bulk and at the interfaces with electron and hole transport layers play a critical role in initiating degradation processes and performance losses. Mitigating defect formation is therefore essential for stabilizing PSCs. This review highlights defect‐induced instability mechanisms associated with ion migration, lattice distortion, and surface chemistry. Furthermore, we discuss recent physical and chemical passivation strategies that enhance device stability without compromising efficiency.

Tin halide formulations are emerging as the leading sustainable, lead-free options for thin-film perovskite solar cells. In this study, we focused on the fully inorganic CsSnI3 composition and systematically explored a solvent-free approach to manufacturing device-grade films via sequential thermal evaporation under vacuum. This production technique is compatible with industry standards, offers fewer constraints than coevaporation, and holds great promise for Pb-based perovskite fabrication but has yet to be thoroughly investigated for tin-based formulations. By eliminating solvents, the approach could also prove effective in mitigating the inherent self-p-doping of these materials, a critical requirement for achieving high-efficiency devices. We tested both double- and multilayer fabrication protocols and compared the structural, morphological, optical, and electrical properties of as-deposited and annealed films. This investigation was complemented by integrating the evaporated CsSnI3 layers into p-i-n solar cells as a diagnostic tool. Our findings provide insights into (i) the impact of the deposition protocol on the material properties and (ii) the potential for fine-tuning them via postdeposition thermal treatments. Both methods yielded highly crystalline and compact films, while self-p-doping persisted in pure stoichiometric CsSnI3 films, with a free hole density of around 1019 cm-3 regardless of the protocol. Notably, a 1-order-of-magnitude reduction in the hole density was achieved by incorporating SnF2 as a reducing agent. Readily implemented via the deposition of an additional layer, the inclusion of additives emerges as a necessary yet viable route toward device-grade evaporated CsSnI3.

Buried interface intercation into perovskite bulk improving the performance of DMSO-free tin perovskite solar cells.

Inverted perovskite solar cells (PSCs) employing self-assembled monolayers (SAMs) as hole-selective materials have demonstrated promising device performance. However, SAMs often exhibit disordered orientation and weak interactions with both the perovskite and the transparent conductive oxide (TCO) substrate, which leads to inefficient charge extraction and significant energy losses. Herein, we proposed an integrated molecular design strategy to comprehensively restructure the SAM (MeS-BPADCP): incorporating bisphosphonate anchoring units, aromatic linker moieties, and methylthio (MeS-) terminal groups. This molecule promotes a nearly vertical orientation on the substrate to enhance charge extraction efficiency by employing bisphosphonate anchoring and aromatic linker, and the methylthio group can effectively passivate surface defects on the perovskite and enhance interface contact. Consequently, the MeS-BPADCP based device achieved a remarkable power conversion efficiency (PCE) of 26.73% and exhibited excellent long-term stability, while sustaining 94.2% of its initial efficiency after continuous operation under one-sun illumination for 1000 h. The device also displayed outstanding thermal cycling stability, retaining 93.3% of its initial PCE after 240 cycles within a temperature range of -40 degrees C to 85 degrees C (ISOS-T-3 protocol).

Realizing stable and scalable perovskite solar cells (PSCs) under real-world outdoor conditions remains a challenge for deployment. Here we report a strategy to improve the resilience of the grain boundary, achieving simultaneous improvement in the power conversion efficiency and long-term operational durability under realistic light cycling and ultraviolet exposure of PSCs. By integrating photoswitchable isomers at grain boundaries, we suppress lattice bond rupture and defect accumulation during repeated light cycling through light-triggered dynamic damage release. This approach stabilizes the triple-cation lead-based perovskite lattice against photoinduced distortions and degradation pathways. As a result, the PSCs retain over 95% of their initial performance after 2,000 h of ultraviolet-containing light cycling at 65 °C and 500 thermal cycles between -40 °C and 85 °C, and deliver a power conversion efficiency of 27.2% (certified as 26.9%). Our strategy improves the operational stability and commercial viability of triple-cation perovskite photovoltaics.

The efficiency-stability trade-off in perovskite solar cells continues to be challenged by issues such as ion migration and defects at grain boundaries and interfaces. Here we address this challenge by an in situ kinetic processing route using a bifunctional spacer, 2-(prop-2-en-1-ylsulfanyl)ethan-1-amine hydrochloride (PYA). Arresting annealing at a metastable stage enables PYA infiltration along widened grain boundaries and incompletely crystallized buried interfaces, whereas deep-ultraviolet activation crosslinks PYA to form a phase-pure 2D 'nanomesh' that encapsulates three-dimensional grains. This omnidirectional network enables defect passivation across the surface, bulk and interface; suppresses electrostrictive lattice distortion by over 80%; and reduces iodide migration ratio by more than 55%, linking mechanical reinforcement to operational resilience. Devices deliver a power conversion efficiency of 27.37% (certified, 27.01%) and retain over 90% performance after 2,110 h of 1-sun illumination, over 95% after 2,400 h at 85 degrees C in a N2 atmosphere, and 97% after 500 thermal cycles between -40 degrees C and 85 degrees C. These results demonstrate a viable pathway towards inherently stable, high-efficiency perovskite photovoltaics.