Metal halide perovskites: stability under illumination and bias

In this short review, we discuss recent progress in developing better understanding of the segregation in mixed composition metal halide perovskite materials and the closely related phenomenon of ion migration (which occurs in both single phase and mixed perovskites). We focus in particular on electrochemical aspects of these phenomena, since they are particularly relevant for the operational stability of devices. A short overview of the methods to suppress segregation/ion migration is given, followed by a summary of the stability milestones in perovskite solar cells and perovskite light emitting diodes. Finally, future outlooks and challenges are discussed.