Impact of Temperature‐Dependent Hydration Water on Perovskite Solar Cells

Water effect on perovskite solar cells has received growing interest in recent years. A widely accepted view is that moderate water content induces the formation of hydrate phase which enhances the recrystallization of the perovskite. However, the underlying factors which influence the formation of hydrate phase are yet to be investigated. Herein, by controlling the annealing temperature, it is demonstrated that 60 °C is the most suitable temperature for the formation of hydrated perovskite. After further annealing at 120 °C, the resulting perovskite film reveals enhanced crystallinity with a more uniform morphology, contributing to device efficiency above 20%. In addition, the water effect on different types of perovskites is studied and it is concluded that the formation of hydrated perovskite is mainly determined by the cations of the perovskite itself. The findings in this work elucidate the conditions for the formation of hydrated perovskite, contributing to the fabrication of highly efficient perovskite solar cells.