Partial lead substitution as a tool to manage the light-induced recrystallization and photostability of mixed-cation lead halide perovskites

Substitution of Pb²⁺ ions in lead halide perovskite Cs_0.12FA_0.88PbI₃ (FA is formamidinium cation) was investigated to address the issues of its phase stability and photostability. The incorporation of optimally selected Nd³⁺, Tb³⁺ and Er³⁺ cations into Cs_0.12FA_0.88Pb_0.99M_0.02/nI₃ films significantly suppressed the light-induced recrystallization and photodegradation, maintaining the morphology, optical properties and phase composition after 9000 h of light exposure, and improved the efficiency and operational stability of perovskite solar cells.