Crystal Growth Regulation of α‐FAPbI3 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 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. A strategy of 4‐fluorobenzamide (FBAD) molecular controlled perovskite crystallization is proposed to suppress the fast reaction between the FAI and PbI2 for high‐quality α‐FAPbI3 films. The optimized solar cell achieves a champion device power conversion efficiency of 24.08% with excellent stability. This study offers an efficient approach to incorporate the only additive of FBAD to produce high‐quality perovskite films for high‐performance solar cells.