Crystal Growth Regulation of α-FAPbI_3 Perovskite Films for High-Efficiency Solar Cells with Long-Term Stability

摘要

The two-step sequentially deposition strategy has been widely used to producehigh-performance FAPbI_3-based solar cells. However, due to the rapidreaction between PbI_2 and FAI, a dense perovskite film forms on top of thePbI_2 layer immediately and blocks the FAI diffusion into the bottom of thePbI_2 film for a complete reaction, which results in a low-efficiency and limitedreproducibility of perovskite solar cells (PSCs). Here, high-quality α-FAPbI3perovskite films by crystal growth regulation with 4-fluorobenzamide additivesis fabricated. The additives can interact with FAI to suppress the fastreaction between the FAI and PbI_2 and effectively passivate the under-coordinatedPb~(2+) or I- defects. As a result, α-FAPbI3 perovskite films with low trapdensity and large grain size are prepared. The modified PSCs present a highpowerconversion efficiency of 24.08, maintaining 90 of their initial efficiencyafter 1400 h in high humidity. This study provides an efficient strategyof synergistic crystallization and passivation to form high-quality α-FAPbI_3films for high-performance PSCs.