Positive and Negative Effects under Light Illumination in Halide Perovskites

Metal halide perovskites (MHPs) have excellent characteristics and present great potential in a broad range of applications such as solar cells, light‐emitting diodes, and photodetectors. However, the light stability of devices remains an unresolved issue and has received great research attention. Under light illumination, MHPs exhibit various anomalous phenomena, such as photoluminescence (PL) enhancement, defect curing, PL blinking, and phase segregation. These phenomena are commonly considered intimately correlated with the performance and stability of MHP devices. In recent years, significant efforts have been made experimentally and theoretically toward understanding the physical origins of these anomalous effects. However, most research focuses on negative effects while the positive effects are mostly ignored. Herein, the positive effects and the negative effects of light soaking in MHPs are systematically discussed with a classification of the correlated physical mechanisms by specifically focusing on variation occurring in timescale from second to hour, corresponding to the unique ionic–electronic interaction. This intends to provide a new insight into ion effects on excellent properties of perovskites, and deep physical understanding of charge‐carrier and ion dynamics in perovskite, and theoretical guidelines for the fabrication of high‐quality and stability perovskite‐based photovoltaic and photoelectric devices.