Sputtered nickel oxide (NiOx) integrated with a self-assembled monolayer (SAM) as a hole-transport layer represents a promising strategy for the scalable application of inverted (p-i-n) perovskite solar cells. However, the inherent limitations of sputtered NiOx, characterized by insufficient surface functionality, hinder the ordered deposition of SAMs, thereby constraining device performance. Here, we demonstrate a method to achieve uniform NiOx films by controlling the oxygen cooling pressure during the magnetron sputtering process. To further enhance the quality of the interface, we introduce a structural-compensation strategy comprising a sputtered underlayer complemented by a solution-processed hydroxyl-rich overlayer. The magnetron-sputtered bottom layer provides a compact, low-defect contact, while the solution-processed top layer creates a hydroxyl-rich surface, facilitating effective SAM anchoring and decoupling SAM deposition from charge extraction processes. This interfacial engineering not only enhances hole extraction, but also promotes perovskite crystallization, leading to enlarged grain sizes, reduced strain, and suppressed non-radiative recombination. Consequently, the resulting inverted devices deliver high performance across bandgaps and scales: 24.86% and 21.78% for small-area 1.55 and 1.68 eV cells, respectively, and 21.38% for a 12.4 cm2 module based on the 1.55 eV absorber, all with robust operational stability. This work provides a practical and scalable pathway toward high-performance perovskite photovoltaics.

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology due to their remarkable power conversion efficiencies and low-cost fabrication processes. However, their long-term operational stability remains a critical challenge for commercialization. This review systematically examines the intrinsic instability factors inherent to PSCs, with a focus on material defects, ion migration, lattice strain, interface-induced degradation, and unstable precursor solution. Defects and their migration under operational stresses trigger non-radiative recombination and lattice decomposition. Ion migration, exacerbated by electric fields and illumination, leads to phase segregation and electrode corrosion. Lattice strain, originating from thermal expansion mismatch and crystallization processes, significantly influences charge recombination and phase stability. Interfacial energetics and mismatched energy levels further induce charge accumulation and efficiency loss. Additionally, chemical side reactions in precursor solutions introduce impurities and defects that compromise film quality and device longevity. This work consolidates recent advances in understanding these degradation pathways. By addressing these intrinsic challenges, this review aims to guide the development of durable perovskite photovoltaics toward commercial reality.

Flexible kesterite Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaics are attractive for lightweight and portable applications, but their efficiency remains limited by uncontrolled alkali-metal incorporation. Here we elucidate and exploit the distinct and complementary roles of Na and Li in controlling CZTSSe crystallization on flexible substrates. Our results show that Na promotes crystal growth, but its induced Se enrichment simultaneously drives large-scale SnSex phase segregation. The incorporation of Li reshapes the free-energy landscape of Cu-related phases, promoting the formation of CuxSe that consumes Se and thereby suppressing SnSex phase growth while driving ordered phase evolution. This kinetic competition strategy yields high-quality CZTSSe films with reduced charge recombination loss and enables power conversion efficiencies of 14.5% (certified 14.2%) for flexible cells and 12.7% (certified 12.0%) for shingled modules. Our results provide mechanistic insights into alkali-metal regulation in chalcogenide solar cells and demonstrate a kinetic competition strategy that can be generalized to regulate crystallization in complex multinary materials.

The interfacial defect challenge between perovskite and electron transport layer (ETL) in inverted perovskite solar cells have become a critical bottleneck for achieving concurrent high efficiency and stability in the process of industrialization. We developed a novel multifunctional integrated polymer semiconductor material P4N-Cl as an interface interlayer between perovskite and [6,6]-phenyl-C61-butyric acid methyl ester. Various functional groups including carbonyl group, Cl atom and sp2-N atom in the polymer backbone effectively passivate defects at the perovskite interface through a synergistic coordination mechanism and significantly suppress non-radiative recombination losses. Simultaneously, the robust interfacial binding at the heterointerface further optimizes the energy level alignment at the perovskite/ETL interface and enhances charge carrier dynamics. The inverted PSCs based on the P4N-Cl multifunctional layer achieved a champion efficiency of 26.20% and a high open-circuit voltage of 1.21 V. The target devices retained 96.2% and 90.2% of their initial power conversion efficiency after 2016 h aging in ambient air (40%-60% relative humidity) and 1500 h maximum power point tracking at 65°C under 1-sun illumination in nitrogen, respectively. This "one-stop" design provides exciting research prospects for constructing a new generation of commercially viable perovskite solar cells with high efficiency and long-term operation stability of devices.

Flexible perovskite solar cells (F-PSCs) exhibit much wider application scope due to the advantages of being light weight, portable, bendable, compatible with curved surfaces, etc. However, unsatisfactory efficiency and mechanical stability severely restrain their further development. Here, an interfacial adhesion strategy is reported to improve the mechanical stability of n-i-p-type F-PSCs. Poly-ECA is inserted between the perovskite layer and SnO2 layer by the self-polymerization of ethyl alpha-cyanoacrylate (ECA) under mild conditions. Strong interactions between poly-ECA and the SnO2/perovskite layer can enhance the mechanical strength of the buried interface. In addition, interfacial defects are also passivated and the energy level alignment at the perovskite interface bottom is optimized, thus facilitating charge transportation. Based on this interfacial adhesion strategy, 25.7% PCE has been achieved with a certified PCE of 25.04% for small-area flexible PSC devices, and 21.9% PCE has been obtained for large-area F-PSC modules (aperture area: 22.55 cm2). Additionally, device stability, particularly mechanical stability, has been significantly improved, and 95% of the initial efficiency can be maintained by small-area devices after 10 000 bending cycles. This work provides a simple, convenient way to simultaneously enhance the efficiency and stability of flexible devices.

Kesterite, Cu2ZnSn(S,Se)4 (CZTSSe), is an earth-abundant, non-toxic material for thin-film photovoltaics, with record certified device efficiencies rising 27% from 13.0% in 2021 to 16.6% in 2025. In this Review, we discuss the technological developments that are renewing momentum in CZTSSe photovoltaics research. Improved thermodynamic–kinetic understanding of multiphase evolution during selenization, together with refined control of precursor homogenization, intermediate phase formation, cation disorder and atomic diffusion, has enabled substantial suppression of deep defects and underpinned the rise in device efficiency. We discuss the mechanisms that historically limited performance, assess which bottlenecks may have been partially alleviated and examine strategies for further efficiency improvements, including further defect regulation and rear-field engineering. We synthesize a framework linking crystallization dynamics, defect physics and device energetics to indicate as possible routes towards efficiencies above 20%. By positioning CZTSSe within the broader context of resource use and tandem integration, we discuss its prospects as a scalable platform for next-generation inorganic thin-film photovoltaics. Kesterites have re-emerged as a promising earth-abundant thin-film photovoltaic technology. This Review describes how advances in crystallization control, defect suppression, atomic ordering and rear-interface engineering could enable progress to efficiencies that surpass 20%

ABSTRACT Interfacial engineering has been widely used to reduce interfacial non‐radiative recombination and enhance the performance of perovskite solar cells (PSCs), but stability issue of interfacial passivation itself has been seldom explored. Herein, we design two halide imidazolium‐based molecules with halogen octyl chains (X8C‐mImX, X = Br, I) for n‐i‐p typed PSCs. It is found that 2D/3D heterojunction structure based on substituted imidazolium cations is formed at the perovskite/spiro‐OMeTAD interface, which effectively passivates interface defects. Meanwhile, free Br − and I − ions can passivate iodide‐vacancy‐related defects at the interfaces, while Br − ions can further contribute to defect passivation in the bulk. With the synergistic effects of the mixed I8C‐mImI/Br8C‐mImBr (I/Br‐mIm), small‐area PSC device presents 26.33% efficiency with negligible hysteresis. Typically, the 2D phase (I/Br‐mIm) 2 PbI 4 , exhibits excellent thermal stability to guarantee the stability of the interface passivation. Accordingly, modified devices exhibit better thermal stability by maintaining 92% of initial efficiency after 1200 h at 85°C. The devices also retain 90% of initial efficiency after 1000 h continuous illumination with a bias voltage close to maximum power point (MPP), indicating its good operational stability. This work provides a feasible way to enhance interface stability and overall device stability by selecting suitable post‐treatment materials.

Targeting at high quality FAPbI(3) films and efficient FAPbI(3) perovskite solar cells, simultaneously regulating perovskite crystal growth and passivating defects from the bulk and interfaces are particularly important. In this respect, we designed two imidazolium-based additives (ImXBr-BF4, X = 8, 12) with different bromoalkyl chain length for n-i-p typed PSCs. Based on experimental and theoretical calculation, Im8Br-BF4 with its optimal chain length enables the formation of ordered layered 2D perovskite. Further investigation revealed that, to the Im8Br-BF4 treated PSCs, as-formed 2D perovskite ((Im8Br)(2)PbI4) mainly at grain boundaries, can well passivate lead-related defects, in the meantime, the Br- from bromoalkyl group also passivated iodide vacancies in the bulk. Besides, the BF4- anions were contributed to partial interfacial passivation toward the buried interface. Consequently, devices with Im8Br-BF4 presented the 26.2 % PCE (0.076 cm(2)), outperforming those devices with Im12Br-BF4. And the devices also exhibited exceptional humidity stability, retaining > 90 % of its initial efficiency after 1000 h at 60 degrees C/60 %RH without encapsulation. Our multi-dimensional passivation strategy provided a simple and feasible way to enhance the device performance of PSCs.

Environmentally benign and earth-abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have advanced rapidly through solution-based processing. However, scaling from laboratory-scale devices to modules remains a major challenge, largely because complex coordination networks in the precursors hinder the formation of uniform large-area films. Here we show that molecular-level regulation of metal-organic coordination can suppress the formation of cross-linked networks in precursor solutions, promoting efficient solvent removal and uniform selenization and crystallization. This coordination-controlled strategy enables the blade coating of highly homogeneous films over 10 cm2, realizing certified efficiencies of 14.2% for 1 cm2 cells and 13.0% for 10.5 cm2 modules, representing a leap-forward improvement in scalable kesterite photovoltaics. Beyond performance, the provided molecular insights into kesterite solution chemistry facilitate establishing a scalable and low-cost route towards industrial deployment of this thin-film solar technology.

ABSTRACT Perovskite solar cells with a typical layered structure, defects and unsatisfied energy band arrangement at the interfaces have significantly affected carrier extraction/transportation even device stability. Therefore, appropriate interface modification is essential for constructing efficient and stable devices. In this work, we designed two asymmetric SAM materials, LW‐1 and LW‐2, to regulate the bottom interface of inverted perovskite solar cells, including passivating the FTO/SAM buried interface and the bottom interface of perovskite films by their substituted groups (Cl − and S 2− ). Typically, Cl − substitution positions were found to have remarkable impact on dipole moment and interfacial properties, and detailed discussion about these effects has been carried out. More uniform perovskite grains and higher crystallinity on the LW‐1 substrate were obtained, thus leading to lower trap densities of the perovskite bulk and the perovskite interface and higher charge collection efficiency ( η C ). Consequently, LW‐1 based devices exhibited 26.38% efficiency, outperforming corresponding LW‐2 based devices. Moreover, LW‐1 based devices exhibited steady‐state output efficiency of 26.0% and maintained 90.9% of its original efficiency after 500 h MPP operational stability testing under 60 °C heating, continuous illumination from a white LED lamp and bias voltage close to the maximum power point voltages.

The performance of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is critically governed by the quality of the CZTSSe/CdS heterojunction; however, the morphology, crystallinity, and defect landscape of CdS buffer layers are intrinsically constrained by the inevitable competition between homogeneous and heterogeneous nucleation in widely used chemical bath deposition (CBD). Here, we report a simple yet effective surface microstructural reconstruction strategy based on chemical polishing that overcomes these challenges beyond the reach of conventional CBD process regulation. Specifically, polishing CZTSSe/CdS films with a Na2S/thiourea aqueous solution selectively removes low-quality CdS particulates while inducing surface recrystallization and sulfur-vacancy compensation. As a result, the CdS films exhibit markedly improved microstructure, enhanced crystallinity, and more homogeneous surface electrical properties. Benefiting from suppressed interfacial charge recombination and accelerated charge transport, kesterite solar cells achieve a champion efficiency of 15.3% with a high open-circuit voltage (VOC) of 560 mV and a record-low VOC deficit (Eg/e-VOC) of < 0.5 V, significantly advancing kesterite photovoltaics toward low voltage loss. Moreover, this work establishes a broadly applicable post-deposition paradigm for improving CBD-CdS-based optoelectronic devices across a wide range of material systems and applications.

Precise control of point defects is imperative for enhancing the performance of emerging kesterite solar cells, yet remains challenging in the multinary Cu2ZnSn(S,Se)4 (CZTSSe) due to its complex defect chemistry. Here, guided by the correlation between phase-evolution kinetics and defect formation, we identify that the delayed formation of Cu2SnSe3 (CTSe) relative to ZnSe during selenization promotes Zn-related antisite defects, including SnZn and CuZn. To rebalance these competing phases, we develop a sodium-activated selenization strategy by pre-constructing reactive Na-Sex species and introducing them into the selenization process. This approach accelerates CTSe formation at lower temperatures, drives the synergistic ZnSe-CTSe transformation toward the CZTSSe phase, and effectively suppresses defect generation. Consequently, a certified power conversion efficiency of 15.1% is achieved with substantially reduced voltage loss, surpassing the commercialization threshold and opening opportunities for scalable inorganic photovoltaics.

The early-stage uniformity and stability of selenium (Se) vapor during selenization critically determine the power conversion efficiency (PCE) of Cu2ZnSn(S,Se)(4) (CZTSSe) devices. However, traditional large-volume graphite chambers (Ctrl) provide an overly spacious diffusion environment, leading to delayed Se supply and concentration fluctuations that promote void defects and Cu-Zn disorder. To address this, we propose a small-sized graphite box (S-box) that stabilizes Se delivery at the source by confining the diffusion volume, shortening the mass-transport path, and accelerating concentration equilibration. COMSOL Multiphysics simulations verify that this design markedly improves diffusion efficiency and rapidly establishes a stable concentration field; correspondingly, experiments show that S-box films exhibit higher crystallinity, reduced Sn2+ content, a denser bilayer structure with fewer voids, and a significantly lower overall defect density. Low-temperature photoluminescence further indicates that non-radiative recombination associated with V-Cu and band tail states is effectively suppressed. Accordingly, devices fabricated with the S-box achieve a champion efficiency of 14.33% (certified at 14.07%), establishing "restricting the Se vapor diffusion space" as the key point of selenization optimization.

To CsPbI3 perovskite solar cells, defects from buried interfaces and improper energy band alignment can cause severe carrier recombination and hamper further enhancement in efficiency and stability. In this work, we develop an in situ strategy to reconstruct the buried interface for n-i-p typed CsPbI3 solar cells. This strategy is derived from an in situ exchange reaction between 18C6/Cs+ and Pb2+, leading to the formation of 18C6/Pb2+ in the CsPbI3 crystallization process (18C6: 18-crown-6 ether). The as-prepared 18C6/Pb2+ complex acts as a kind of molecular barrier to modify the TiO2/perovskite buried interface and passivate under-coordinated Pb2+ and iodide vacancies. Additionally, free Br- ions can diffuse into the lattice of the CsPbI3 film bottom, forming a front-surface field to further suppress carrier recombination. Based on this strategy, as high as 22.14% efficiency has been achieved, demonstrating one of the highest efficiencies of CsPbI3 perovskite solar cells to date. Besides, the modified cell can maintain 95% of its initial efficiency after 1500 h of MPP testing and 1500 h of long-term stability testing, exhibiting excellent operational stability.

The interface contact issue, surface defects, and energy level mismatches have significantly limited the optoelectronic performance of solution-processed transparent conductive window layers for use in thin-film solar cells. In this work, these challenges are systematically addressed by employing molecular engineering to regulate the multiple interfaces of ZnO nanoparticles (ZnO-nps)/silver nanowires (AgNWs) window layers in kesterite solar cells. The interface molecular engineering enhances the conformal deposition of ZnO-nps on rough Cu2ZnSn(S, Se)4 (CZTSSe)/CdS substrates, passivates hydroxyl defects in ZnO-nps, and optimizes energy level alignment at the ZnO-nps/AgNWs interface. These advancements enable us to achieve a certified total area efficiency of 14.3%, marking a significant milestone for all-solution-processed kesterite solar cells. Furthermore, the solution-processed window layer forms a robust and flexion-tolerant lateral conductive network, imparting excellent flexibility to the cells. This development provides a critical technical foundation to support the low-cost and simpler preparation of thin-film solar cells in future commercialization.

CsPbI 3 perovskites with suitable bandgaps ∼1.70 eV present distinct advantages for top-cell photovoltaic materials in tandem solar cells, however, relevant work has been rarely reported. This work designed a sandwich-like MoO X /Ag/MoO X (MAM) buffer layer as the front cell window layer to maximize incident light utilization efficiency for semi-transparent CsPbI 3 solar cells and four terminal (4-T) stacked cells. Further investigation revealed that the MAM has to experience in-situ reaction between Ag metal and fresh MoO X , which can simultaneously ensure the transparency of the buffer layer and improve the carrier transportation and collection, except for protecting the underlying spiro-OMeTAD layer from the bombardment of magnetron sputtering. Thanks to this MAM buffer layer and a tunnel oxide passivating contact (TOPCon) bottom cell with edge passivation, semi-transparent CsPbI 3 devices (aperture area: 0.50 cm 2 ) demonstrated a power conversion efficiency (PCE) of 18.86% while corresponding 4-T CsPbI 3 /TOPCon tandem solar cells (PSTSCs) presented the PCE of 26.55%. Besides, we also fabricated semi-transparent CsPbI 3 minimodules with 16.67% PCE and 4-T PSTSCs with 26.41% PCE (aperture area: 6.62 cm 2 ). This work provided a new scalable strategy for transparent buffer layers by constructing in-situ generated sandwich structured buffer layer, which is suitable for perovskite tandem solar cells.

CsPbI3 perovskites with suitable bandgaps similar to 1.70 eV present distinct advantages for top-cell photovoltaic materials in tandem solar cells, however, relevant work has been rarely reported. This work designed a sandwich-like MoOX/Ag/MoOX (MAM) buffer layer as the front cell window layer to maximize incident light utilization efficiency for semi-transparent CsPbI3 solar cells and four terminal (4-T) stacked cells. Further investigation revealed that the MAM has to experience in-situ reaction between Ag metal and fresh MoOX, which can simultaneously ensure the transparency of the buffer layer and improve the carrier transportation and collection, except for protecting the underlying spiro-OMeTAD layer from the bombardment of magnetron sputtering. Thanks to this MAM buffer layer and a tunnel oxide passivating contact (TOPCon) bottom cell with edge passivation, semi-transparent CsPbI3 devices (aperture area: 0.50 cm(2)) demonstrated a power conversion efficiency (PCE) of 18.86% while corresponding 4-T CsPbI3/TOPCon tandem solar cells (PSTSCs) presented the PCE of 26.55%. Besides, we also fabricated semi-transparent CsPbI3 minimodules with 16.67% PCE and 4-T PSTSCs with 26.41% PCE (aperture area: 6.62 cm(2)). This work provided a new scalable strategy for transparent buffer layers by constructing in-situ generated sandwich structured buffer layer, which is suitable for perovskite tandem solar cells.

This review explores the role of perovskite inks and their impact on the quality of scalable perovskite films. Factors such as fluid dynamics, solvent selection, and additive engineering during the meniscus-assisted coating process are summarized.