Crystal Growth Regulation of α‐FAPbI 3 Perovskite Films for High‐Efficiency Solar Cells with Long‐Term Stability

The two‐step sequentially deposition strategy has been widely used to produce high‐performance FAPbI 3 ‐based solar cells. However, due to the rapid reaction between PbI 2 and FAI, a dense perovskite film forms on top of the PbI 2 layer immediately and blocks the FAI diffusion into the bottom of the PbI 2 film for a complete reaction, which results in a low‐efficiency and limited reproducibility of perovskite solar cells (PSCs). Here, high‐quality α‐FAPbI 3 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 PbI 2 and effectively passivate the under‐coordinated Pb 2+ or I ‐ defects. As a result, α‐FAPbI 3 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‐FAPbI 3 films for high‐performance PSCs.