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The perovskite solar cells (PSCs) are promising for commercialization and practical application. However, high‐quality perovskite films are normally fabricated in inert gas‐filled glovebox, followed by thermal annealing, which is energy‐consuming and thus not cost‐effective. In this study, a simple manufacturing strategy is demonstrated to fabricate the highly‐crystalline perovskite films in ambient air (a relative humidity of over ≈50%) at room temperature via blade‐coating without the subsequent thermal–annealing. The perovskite precursor chemistry is tailored by solvent engineering via employing 2‐methoxyethanol, which can strongly coordinate with ammonium halide species, thus forming highly uniform small‐sized colloids and facilitating the homogeneous nucleation and rapid crystallization of perovskite films even at room temperature. The resultant PSCs fabricated with ambient‐processed, annealing‐free MAPbI3 perovskite films exhibit a champion efficiency up to 19.16% with negligible hysteresis and improved reproducibility, which is on par with the high‐temperature annealed counterparts fabricated in N2, and represented one of the highest reported efficiencies for the room‐temperature processed PSCs in ambient air. The unencapsulated devices show extended lifespan over 1000 h with nearly no efficiency loss. [ABSTRACT FROM AUTHOR]

The interface between the electron transport layer (ETL) and the perovskite film plays a vital role in the performance of perovskite solar cells (PSCs). Here, (2-hydroxyethyl)amine hydroiodide (EOAI) is employed to regulate the interface properties at the SnO2/perovskite. The –NH3+ positive and I− negative ion groups in EOAI, which are anchored on the surface of SnO2 through –OH groups, can passivate the interface defects of perovskite films. Besides, the modified ETL has a smaller work function (WF) and EVB than pristine ones, which contributes to efficient charge transport and collection. Furthermore, the introduction of EOAI can also improve the crystallinity of the perovskite layer. As a result, PSCs with EOAI-modified SnO2 produce a champion power conversion efficiency (PCE) of 22.61%, and an improved environmental stability. At the same time, the 1.68 eV wide-band gap perovskite solar cell achieved a PCE close to 20% and the semitransparent device also achieved an efficiency of over 17%. [ABSTRACT FROM AUTHOR]

In the past decade, perovskite solar cell (PSC) photoelectric conversion efficiency has advanced significantly, and tin dioxide (SnO 2 ) has been extensively used as the electron transport layer (ETL). Due to its high electron mobility, strong chemical stability, energy level matching with perovskite, and easy low-temperature fabrication, SnO 2 is one of the most effective ETL materials. However, the SnO 2 material as an ETL has its limitations. For example, SnO 2 films prepared by low-temperature spin-coating contain a large number of oxygen vacancies, resulting in energy loss and high open-circuit voltage ( V OC ) loss. In addition, the crystal quality of perovskites is closely related to the substrate, and the disordered crystal orientation will lead to ion migration, resulting in a large number of uncoordinated Pb 2+ defects. Therefore, interface optimization is essential to improve the efficiency and stability of the PSC. In this work, 2-(5-chloro-2-benzotriazolyl)-6- tert -butyl-p-cresol (CBTBC) was introduced for ETL modification. On the one hand, the hydroxyl group of CBTBC forms a Lewis mixture with the Sn atom, which reduces the oxygen vacancy defect and prevents nonradiative recombination. On the other hand, the SnO 2 /CBTBC interface can effectively improve the crystal orientation of perovskite by influencing the crystallization kinetics of perovskite, and the nitrogen element in CBTBC can effectively passivate the uncoordinated Pb 2+ defects at the SnO 2 /perovskite interface. Finally, the prevailing PCE of PSC (1.68 eV) modified by CBTBC was 20.34% ( V OC = 1.214 V, J SC = 20.49 mA/cm 2 , FF = 82.49%).

Mixed-cation, small band-gap perovskites via rationally alloying formamidinium (FA) and methylammonium (MA) together have been widely employed for blade-coated perovskite solar cells with satisfied efficiencies. One of the stringent challenges lies in difficult control of the nucleation and crystallization kinetics of the perovskites with mixed ingredients. Herein, a pre-seeding strategy by mixing FAPbI 3 solution with pre-synthesized MAPbI 3 microcrystals has been developed to smartly decouple the nucleation and crystallization process. As a result, the time window of initialized crystallization has been greatly extended by 3 folds (i.e. from 5 s to 20 s), which enables the formation of uniform and homogeneous alloyed-FAMA perovskite films with designated stoichiometric ratios. The resultant blade-coated solar cells achieved a champion efficiency of 24.31 % accompanied by outstanding reproducibility with more than 87 % of the devices showing efficiencies higher than 23 %., (© 2023 Wiley-VCH GmbH.)

The high density of defects in MAPbI 3 perovskite films brings about severe carrier nonradiative recombination loss, which lowers the performance of MAPbI 3 -based perovskite solar cells (PSCs). Here, methylamine cyanate (MAOCN) molecules were introduced into MAPbI 3 solutions to manipulate the crystallizatsion of the MAPbI 3 films. MAOCN molecules can slow down the volatilization rate of the solvent and delay the crystallization process of the MAPbI 3 film. The crystal quality of the MAPbI 3 films is effectively optimized without an additive residue. Perovskite films treated by MAOCN have lower defect density and longer carrier lifetime, which lowers the carrier recombination loss. Meanwhile, the MAPbI 3 film based on MAOCN has a more hydrophobic surface. The final MAPbI 3 -based device efficiency reached 21.28% ( V OC = 1.126 V, J SC = 23.29 mA/cm 2 , and FF = 81.13). After 30 days of storage under atmospheric conditions, the efficiency of unencapsulated MAOCN-based PSCs only dropped by about 5%.