Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies owing to their exceptional optoelectronic properties^1,2. However, the lower efficiency, poor stability and reproducibility issues of large-area PSCs compared with laboratory-scale PSCs are notable drawbacks that hinder their commercialization³. Here we report a synergistic dopant-additive combination strategy using methylammonium chloride (MACl) as the dopant and a Lewis-basic ionic-liquid additive, 1,3-bis(cyanomethyl)imidazolium chloride ([Bcmim]Cl). This strategy effectively inhibits the degradation of the perovskite precursor solution (PPS), suppresses the aggregation of MACl and results in phase-homogeneous and stable perovskite films with high crystallinity and fewer defects. This approach enabled the fabrication of perovskite solar modules (PSMs) that achieved a certified efficiency of 23.30% and ultimately stabilized at 22.97% over a 27.22-cm² aperture area, marking the highest certified PSM performance. Furthermore, the PSMs showed long-term operational stability, maintaining 94.66% of the initial efficiency after 1,000 h under continuous one-sun illumination at room temperature. The interaction between [Bcmim]Cl and MACl was extensively studied to unravel the mechanism leading to an enhancement of device properties. Our approach holds substantial promise for bridging the benchtop-to-rooftop gap and advancing the production and commercialization of large-area perovskite photovoltaics.

Surface passivation of the perovskite photo absorber is a key factor to improve the photovoltaic performance. So far robust passivation strategies have not yet been revealed. Here, we demonstrate a successful passivation strategy which controls the Fermi-level of the perovskite surface by improving the surface states. Such Fermi-level control caused band-bending between the surface and bulk of the perovskite, which enhanced the hole-extraction from the absorber bulk to the HTM side. As an added benefit, the inorganic passivation layer improved the device light stability. By depositing a thick protection layer on the complete device, a remarkable waterproofing effect was obtained. As a result, an enhancement of V_OC and the conversion efficiency from 20.5% to 22.1% was achieved. We revealed these passivation mechanisms and used perhydropoly(silazane) (PHPS) derived silica to control the perovskite surface states.

Interface engineering and passivating contacts are key enablers to reach the highest efficiencies in photovoltaic devices. While printed carbon–graphite back electrodes for hole‐transporting material (HTM)‐free perovskite solar cells (PSCs) are appealing for fast commercialization of PSCs due to low processing costs and extraordinary stability, this device architecture so far suffers from severe performance losses at the back electrode interface. Herein, a 2D perovskite passivation layer as an electron blocking layer (EBL) at this interface to substantially reduce interfacial recombination losses is introduced. The formation of the 2D perovskite EBL is confirmed through X‐ray diffraction, photoemission spectroscopy, and an advanced spectrally resolved photoluminescence microscopy mapping technique. Reduced losses that lead to an enhanced fill factor and V_OC are quantified by electrochemical impedance spectroscopy and J_SC–V_OC measurements. This enables reaching one of the highest reported efficiencies of 18.5% for HTM‐free PSCs using 2D perovskite as an EBL with a significantly improved device stability.

All-inorganic CsPbI ₃ perovskite solar cells (PSCs) with efficiencies exceeding 20% are ideal candidates for application in large-scale tandem solar cells. However, there are still two major obstacles hindering their scale-up: (i) the inhomogeneous solid-state synthesis process and (ii) the inferior stability of the photoactive CsPbI ₃ black phase. Here, we have used a thermally stable ionic liquid, bis (triphenylphosphine)iminium bis (trifluoromethylsulfonyl)imide ([PPN][TFSI]), to retard the high-temperature solid-state reaction between Cs ₄ PbI ₆ and DMAPbI ₃ [dimethylammonium (DMA)], which enables the preparation of high-quality and large-area CsPbI ₃ films in the air. Because of the strong Pb-O contacts, [PPN][TFSI] increases the formation energy of superficial vacancies and prevents the undesired phase degradation of CsPbI ₃ . The resulting PSCs attained a power conversion efficiency (PCE) of 20.64% (certified 19.69%) with long-term operational stability over 1000 hours. A record efficiency of 16.89% for an all-inorganic perovskite solar module was achieved, with an active area of 28.17 cm ² .

In the inverted structure perovskite solar cells, a buffer layer is generally used at the interface between the n-type semiconductor layer and the metal electrode, but its design guidelines have not yet been established. Here, a series of inverted perovskite solar cells have been fabricated with the controlled thickness of bathocuproine (BCP) buffer layers deposited by thermal evaporation and validated the BCP buffer layer evaluation tool. The ideal factor was calculated from the gradient in the plot of Voc against the log of Jsc, and the effect of the BCP buffer layer on charge recombination was verified. Since the ideal factor greatly decreased from 5 to 1.4 by introducing the BCP buffer layer, it was confirmed that the interface between the n-type semiconductor layer and the metal electrode gradually changed from a Schottky barrier diode to an ohmic contact. On the other hand, it was found that an excessive BCP film thickness causes the series resistance to increase and induced recombination. Finally, as a result of optimizing the perovskite layer and the BCP buffer layer, respectively, the performance exceeding 17% was obtained. This study provides insight into the improvements in the conversion efficiency of perovskite solar cells by optimizing the thickness of the buffer layer using the ideal factor.

Organic–inorganic lead halide perovskites with over 23% power conversion efficiency have attracted enormous academic and industrial attention due to their low-cost fabrication and high device performance. Self-passivated tin oxide as an electron transport layer has shown potential mainly due to the enhanced electron transfer, stability and reduced hysteresis device features. Here we report on novel, non-colloidal tin oxide precursors based on acetylacetonate (one halide free and two halogenated with Cl and Br respectively). We explore the unique film morphology acquired from the non-colloidal precursors and the improved device performance they yield. Our results show that the halide residue in the films plays an impactful role in the thermal durability of the fabricated SnO₂ film, as well as providing a passivation layer. Moreover, our optimized tin oxide films achieved an unprecedented power conversion efficiency of 22.19% in planar perovskite solar cells (21.4% certified by Newport), and once upscaled to large-area modules, 16.7% devices based on a 15 cm² area were achieved.