Although the published values of power conversion efficiency (PCE) have increased continuously in recent years for perovskite solar cells (PSCs), improvements in the stability and performance of PSCs with conventional TiO2 or SnO2 electron transport layers (ETLs) remain limited by the presence of nonideal interface defects and low ultraviolet (UV) absorption. In this study, 2-hydroxy-4-methoxy-5-sulfonate-benzophenone (SBP), an inexpensive water-soluble sunscreen raw material, was incorporated into the SnO2 ETL as a UV filter. It was found that the exposure of perovskite to UV light was significantly reduced, and, more importantly, the carbonyl and sulfonic acid groups in the SBP influenced both the perovskite crystallization process and the passivation of defects in the ETL/perovskite film interface. As a result, the PCE of SBP-based devices was increased to 22.54% from 20.78% of the control sample, with a concomitant decrease in the hysteresis. Moreover, the efficiency of champion devices with SBP decreased by less than 5% after 200 h of continuous UV (1.63 mW/cm2, 285 nm) irradiation, while the control group dropped to below 75% of the initial value, thus showing significantly improved stability.