Stabilized Wide Bandgap Perovskite Solar Cells by Tin Substitution

Wide bandgap MAPb(I1-yBry)(3) perovskites show promising potential for application in tandem solar cells. However, unstable photovoltaic performance caused by phase segregation has been observed under illumination when y is above 0.2. Herein, we successfully demonstrate stabilization of the I/Br phase by partially replacing Pb2+ with Sn2+ and verify this stabilization with X-ray diffractometry and transient absorption spectroscopy. The resulting MAPb(0.75)Sn(0.25)(I1-yBry)(3) perovskite solar cells show stable photovoltaic performance under continuous illumination. Among these cells, the one based on MAPb(0.75)Sn(0.25)(I0.4Br0.6)(3) perovskite shows the highest efficiency of 12.59% with a bandgap of 1.73 eV, which make it a promising wide bandgap candidate for application in tandem solar cells. The engineering of internal bonding environment by partial Sn substitution is believed to be the main reason for making MAPb(0.75)Sn(0.25)(I1-yBry)(3) perovskite less vulnerable to phase segregation during the photostriction under illumination. Therefore, this study establishes composition engineering of the metal site as a promising strategy to impart phase stability in hybrid perovskites under illumination.