Recent progress of ion migration in organometal halide perovskite

In recent years, metal halide perovskite solar cells have attracted widespread attention due to their unique technological superiority. Remarkable progress of device performance has been achieved in last few years. The certified efficiency has reached 24.2%, which is close to the efficiency of the commercial crystalline silicon solar cells. Halide perovskite is a kind of semiconductor and ionic conductor material, which not only has the ability to transfer charges, but also exhibits the phenomenon of ion migration under an external electric field. Ion migration can directly change the local chemical ratio of perovskite crystals, and can also greatly affect the electrical properties of materials and the working mechanisms of corresponding devices. In this review, the formation mechanism, basic characteristics and effects of ion migration on the working mechanism of the device (such as giant switchable photovoltaic phenomenon, current hysteresis, etc.) are summarized, and then some recent advances in the suppression of ion migration are introduced. Since there exist still many doubts about ion migration in perovskite materials, it is very important to understand the phenomenon of ion migration in perovskite materials in order to promote the development and application of perovskite solar cells.