Ion migration in hybrid perovskites: Classification, identification, and manipulation

Photovoltaic devices based on metal hybrid perovskite materials have been extensively explored in recent years for the exceptional power-conversion efficiency and the potential application in achieving carbon neutrality. Nevertheless, the intrinsic stability issues caused by ion migration seriously hinders further performance development and large-scale commercialized production of perovskite solar cells. The recent efforts to coping with ion migration in hybrid perovskites and related progress as well as challenges are urgent to be reviewed. Herein, we first discuss the source and origin of ion migration behavior and corresponding effect on device performance and stability. Advanced characterization techniques are comprehensively summarized for their great importance in confirming the migrating ability, distinguishing the moving species, identifying the migrating route and investigating the impact of ion migration. We exhaustively compare their working principles, applying scopes and striking features, highlighting the applicability and limitations in typical experimental conditions. Beyond that, the effective strategies to govern ion migration in perovskite solar cells from the perspective of active layer component engineering, dimensional engineering and device structure design are systemically assessed. Finally, we propose some open questions in terms of characterizing and modulating ion migration and outline potential solution strategies those will advance the research of hybrid perovskites-related fields.