Mixed-halide Pb-Sn binary perovskite films with various Sn-content for Pb-reduced solar cells

We proposed and examined a material group of methylammonium Pb-Sn mixed halide (MAPb1−xSnxI2.6Br0.4) with various Sn-content (x = 0.2-0.8) for Pb-reduced perovskite solar cells. With suitable Pb-Sn ratio (x = 0.4-0.6), dense coverage of films with better crystallinity was obtained compared with low Sn ratio (x = 0.2). For excess Sn ratio (x = 0.8), poor film-uniformity was found in spite of its enhanced crystallinity. Optimum composition (x = 0.6) provided an impressive power conversion efficiency of 13.4% with remarkable photocurrent output stability, which is related to suppression of trap-assisted recombination regarding the perovskite materials. This promising material paves the way for development of highly efficient, Pb-reduced perovskite photovoltaic cells.