Stabilizing Precursor Solution and Controlling Crystallization Kinetics Simultaneously for High‐Performance Perovskite Solar Cells

Abstract

The efficiency of metal halide perovskite solar cells (PSCs) has skyrocketed; however, defects created by aging precursor solutions and during crystallization pose a significant barrier to the reproducibility and efficiency of solar cells. In this work, fluoro-N,N,N″,N″-tetramethylformamidinium hexafluorophosphate (F-(CH₃ )₄ CN₂ PF₆ , abbreviated as TFFH) is introduced to stabilize precursor solution and improve crystallization dynamics simultaneously for high-performance formamidinium lead iodide (FAPbI₃ )-based perovskite indoor photovoltaics. The TFFH stabilizes the precursor solution by inhibiting oxidation of I^- and reducing newly generated I⁰ to I^- , and passivates undercoordinated Pb²⁺ by interacting with the Pb─I framework. Time-resolved optical diagnostics show prolonged perovskite crystallization dynamics and in situ defect passivation due to the presence of strong FA⁺ ···TFFH···Pb─I interaction. Simultaneous regulation of precursor solution and crystallization dynamics guarantee larger perovskite grain sizes, better crystal orientation, fewer defects and more efficient charge extraction in PSCs. The optimized PSCs achieve improved reproducibility and better stability and reach an efficiency of 42.43% at illumination of 1002 lux, which is the highest efficiency among all indoor photovoltaics. It is anticipated that the concurrent stabilization of solutions and regulation of crystallization dynamics will emerge as a prevalent approach for enhancing the reproducibility and efficiency of perovskite.