Formamidine Acetate Induces Regulation of Crystallization and Stabilization in Sn-Based Perovskite Solar Cells

Sn-based perovskite solar cells (PSCs) have received extensive attention for photovoltaic applications. Nevertheless, the low crystallization quality of the film due to rapid crystallization results in high trap density of states, which is one of the main reasons for poor performance of Sn-based PSC devices. In this work, we developed a strategy for the formation of FASnI(3) perovskites by introducing the addition of formamidine acetate (FAAc). Benefiting from the iodide-coordinated cation (FA(+)) and crystallization-regulated anion (AC(-)), FAAc could achieve the high-quality films with suppressed defects. The champion power conversion efficiency (PCE) of FAAc-modified PSC devices reached 9.96%, reserving 82% of their initial PCE of the light aging test over 1500 h. We hope that our finding could provide implications on the high-performance and stable Sn-based PSCs.