Tailoring Defects Regulation in Air-Fabricated CsPbI₃ for Efficient Inverted All-Inorganic Perovskite Solar Cells with V_oc of 1.225 V

Air fabrication of CsPbI3 perovskite photovoltaics has been attractive and fast-moving owing to its compatibility to low-cost and up-scalable fabrication. However, due to the inevitable erosions, undesirable traps are formed in air-fabricated CsPbI3 crystals and seriously hinder photovoltaic performance with poor reproduction. Here, 3, 5-difluorobenzoic acid hydrazide (FBJ) is incorporated as trap regulation against external erosions in air-fabricated CsPbI3. Theoretical simulations reveal that FBJ molecules feature stronger absorbance on CsPbI3 than water, which can regulate trap formations for water erosions. In addition, FBJ with solid bonding interaction to CsPbI3 can enlarge formation energy of various defects during crystallization and further suppress traps. Moreover, profiling to reductive hydrazine groups, FBJ inhibits traps for oxidation erosions. Consequently, a champion efficiency of 19.27% with an impressive Voc of 1.225 V is realized with the inverted CsPbI3 devices. Moreover, the optimized devices present superior stability and contain 97.4% after operating at 60 °C for 600 h.