Pinhole Healing of Pristine FAPbI₃ Films via Homogeneous Recrystallization with Mixed Vapor of Tetramethylene Sulfoxide and Anisole

Abstract

The preparation of pristine formamidinium lead tri‐iodide (FAPbI3) perovskite films for solar cells applications can be very challenging without methylammonium containing additives. The pinhole‐rich films prepared by methylammonium‐free approach limit the performance of the pristine FAPbI3 perovskite solar cells (PSCs). This work proposes a recrystallization method employing mixed solvent annealing (MSA) to heal the pinholes in pristine FAPbI3 perovskite films. The tetramethylene sulfoxide vapor is demonstrated most effective in grains‐merging and pinhole healing, while the addition of a secondary solvent vapor of anisole significantly improved the uniformity of TMSO vapor distribution. The pristine FAPbI3 PSCs prepared with MSA recrystallized film achieved power conversion efficiencies up to 22.43% and 16.54% on small cells (0.105 cm2) and mini‐modules (12.6 cm2), respectively, showing great potential in upscaling fabrication of perovskite photovoltaics with pristine FAPbI3.