Crystallization Dynamic Control of Perovskite Films with Suppressed Phase Transition and Reduced Defects for Highly Efficient and Stable All-Inorganic Perovskite Solar Cells

The performance of all-inorganic CsPbBr3 solar cells for photovoltaic applications is governed by the phase compositions of 3D CsPbBr3 and its Cs–Pb–Br derivatives of 0D Cs4PbBr6 or 2D CsPb2Br5. Herein, a general method was proposed by using CsBr/CH3OH treatment to suppress the phase transitions and reduce surface defects of CsPbBr3 films revealed by theoretical calculation and experiments. The formation energies (ΔH) for various phase transition processes verify that low concentration CsBr/CH3OH treatment can effectively inhibit the harmful 0D Cs4PbBr6 formation, further repairing the surface defects of perovskite and improving the photovoltaic performance. The hole transport layer (HTL)-free CsPbBr3 PSC achieves a champion efficiency of 9.48% with an impressive 1.54 V open-circuit voltage and excellent long-term stability. It is worth mentioning that adding a thin ZnO layer on TiO2/CsPbBr3 interface can increase the efficiency of CsPbBr3–PSC to 10.67% with improved short-circuit current and open-circuit voltage. The advanced CsPbBr3-based PSCs can benefit from these insights into accurately controlling the Cs–Pb–Br perovskite phase transition and surface properties.