Crystal Growth Regulation of α‐FAPbI₃ Perovskite Films for High‐Efficiency Solar Cells with Long‐Term Stability

Abstract The two‐step sequentially deposition strategy has been widely used to produce high‐performance FAPbI₃‐based solar cells. However, due to the rapid reaction between PbI₂ and FAI, a dense perovskite film forms on top of the PbI₂ layer immediately and blocks the FAI diffusion into the bottom of the PbI₂ film for a complete reaction, which results in a low‐efficiency and limited reproducibility of perovskite solar cells (PSCs). Here, high‐quality α‐FAPbI₃ perovskite films by crystal growth regulation with 4‐fluorobenzamide additives is fabricated. The additives can interact with FAI to suppress the fast reaction between the FAI and PbI₂ and effectively passivate the under‐coordinated Pb²⁺ or I^‐ defects. As a result, α‐FAPbI₃ perovskite films with low trap density and large grain size are prepared. The modified PSCs present a high‐power conversion efficiency of 24.08%, maintaining 90% of their initial efficiency after 1400 h in high humidity. This study provides an efficient strategy of synergistic crystallization and passivation to form high‐quality α‐FAPbI₃ films for high‐performance PSCs.