Tin-Oxide Perovskites In article number 2200964, Non Thongprong, Thidarat Supasai, Nopporn Rujisamphan, and co-workers presented the pseudohalide salt of sodium tetrafluoroborate, whose anions have a higher electronegativity than other halide salts, with the potential to passivate the surface of tin oxide while enhancing the optoelectronic properties of a perovskite film. The current study presents a facile and effective method for enhancing the moderate thermal stability and performance of solar cell devices.