Repaired surface structural imperfection of tin Wide-Bandgap perovskite films for photovoltaic application

Tin-based perovskite solar cells (Sn-PSCs) are emerging as a potential alternative to lead-based PSCs in order to address issues of theoretical efficiency and toxicity limitations. However, due to the structural imperfections on the surface of perovskite films, the numerous defects can cause severe non-radiative recombination loss, which would reduce the efficiency and operational stability of Sn-PSCs. Herein, we used 4-fluorobenzoyl chloride (4FBC) for surface treatment of tin perovskite films. The introduction of 4FBC passivated the defects, improved the surface morphology, slowed down the formation of SnI2, suppressed the oxidation of Sn2+ from top to bottom, and improved the carrier mobility. Encouragingly, the treated device achieved a champion power conversion efficiency of 11.03 % and significantly improved the open-circuit voltage (VOC) to 0.94 V, the fill factor (FF) to 86.7 %, which both were the highest VOC and FF values reported in wide-bandgap Sn-PSCs (∼1.6 eV) to date. The findings emphasize the importance of surface treatment for tin halide perovskites and serve as a reference for further reducing the voltage loss in wide-bandgap Sn-PSCs.