Simultaneous Passivation of the SnO₂/Perovskite Interface and Perovskite Absorber Layer in Perovskite Solar Cells Using KF Surface Treatment

Recently, SnO2 has been recognized as a promising electron transport layer (ETL) for perovskite solar cells (PSCs) due to its outstanding optoelectronic properties and low-temperature fabricating process. However, the detrimental defects formed at the SnO2/perovskite interface and within bulk perovskite films cause severe non-radiative recombination, limiting the further improvement of power conversion efficiencies (PCEs). Herein, we have demonstrated a facile surface treatment on SnO2 through KF modification to passivate defects at both regions simultaneously. F– ions reduce the detrimental hydroxyl group defects on the SnO2 surface effectively, resulting in improved crystallinity of perovskite films with a more favorable morphology. Meanwhile, a preferred energy level alignment between SnO2 and MAPbI3 films is obtained, improving the carrier transport capability. Moreover, K+ ions can diffuse into the MAPbI3 film, passivating the grain boundaries and intrinsic I– vacancy defects. Consequently, a significant increase in PCE from 18.47 to 20.33% is achieved for a MAPbI3 PSC based on a SnO2/KF ETL, with negligible hysteresis and improved stability.