Ion Migration in Metal Halide Perovskites Solar Cells

Metal halide perovskites (MHPs) have been in the spotlight of the solar cell community in recent years due to their rapid increase in power conversion efficiency. The certified power conversion efficiency of perovskite solar cells (PSCs) has reached a high value of 25.5%, closing to its Shockley–Queisser limit and approaching that of crystalline silicon solar cells. However, it has been acknowledged that ion migration, an intrinsic property of MHPs causing many undesirable changes in PSCs, such as large current-voltage hysteresis curves, poor stability, low conductivity, phase segregation, etc., leads to PSCs degradation. In this chapter, we review ion migration in PSCs. We will cover topics including ion migration species in MHPs, ion migration channels, the factors that influence ion migration, and the effect of ion migration on perovskite solar cells, as well as strategies to suppress ion migration.