Low-Temperature Preparation of CsPbI₂Br for Efficient and Stable Perovskite Solar Cells

Inorganic cesium-based perovskite is an alternative material of organic–inorganic perovskite because of its high thermal stability. However, the phase instability and the high annealing temperature to form α-phase hinder its further development. Herein, this work successfully achieves the reduction of α-phase formation temperature from 350 to 150 °C and achieves high-performance CsPbI2Br-based perovskite solar cells via doping CH3COOCs (CsAc) at optimum concentration. The CsAc-doped CsPbI2Br film fabricated at low temperature of 150 °C exhibits good crystallization and a pinhole-free surface. The function of phase stability by doping CsAc is the grain boundary passivation to decrease defect states and enhance the charge transport. The PSC based on CsAc-doped CsPbI2Br using a planar structure achieves an efficiency of 10.53%, which is three times higher than that of undoped CsPbI2Br fabricated at 150 °C. More importantly, the pure α-phase with CsAc-doped film shows long time stability. This work highlights an available method to prepare high-performance and phase-stable perovskite solar cells at low temperature.