Defect proliferation in CsPbBr₃ crystal induced by ion migration

Ion migration in halide perovskite materials usually brings an intractable problem in the working stability of solar cells and photoelectrical detectors. The mechanism of ion migration and its impact on physical properties are still open questions. In this work, the ion migration behavior in solution-grown CsPbBr₃ crystals was observed by the hysteresis in current-voltage curves and the temperature dependent reversed current-time measurements. Defect proliferation phenomena (new defects of [V_Cs]^- and [Pb_Br]²⁺) originating from ion migration were verified by thermally stimulated current spectroscopy. Our results also give evidence that Cs⁺ ions also participate in the process of ion migration except the widely considered Br^- ions. Furthermore, the photoelectric properties of the CsPbBr₃ device were found to be seriously deteriorated after the ion migration. Our work demonstrates the strong correlation between the ion migration and physical properties in halide perovskites.