Halide Ions Distribution and Charge Dynamics in Mixed‐Halide Perovskites

Owing to the striking properties, perovskite materials have clutched the interest in the field of optoelectronics. The property of being band tunable via composition alteration makes the perovskites fit in many optoelectronic applications. However, the compositional instability of mixed‐halide perovskites (MHPs) under illumination or by charge‐carrier injection is intercepting the exploitation of mixed‐halide strategy which effectively tailors the perovskite's bandgap. Herein, the segregation of halide ions in lattice promotes the formation of individual halide‐rich domains that severely influence the electronic band structures of the MHPs. In this scenario, extensive research is heading to perceive the mechanisms that drive the halide segregation and abate the process accordingly. As the impact of ion segregation directly determines the performance of the devices, in‐depth understanding is a prerequisite. This perspective provides a compressive understanding of different aspects such as structural origin, influence of light intensity, temperature, and atmospheric conditions that root the segregation process. A rigorous analytical discussion on approaches to play with cations and anions compositions, dimensionality, and Lewis base treatment that are detrimental for the halide segregation process is presented. This perspective contains a critical view on the halide segregation process that paves the route for future research.