Emerging Irreversible and Reversible Ion Migrations in Perovskites

Metal halide perovskite (MHP) materials show great prospects in applications such as solar cells, luminescent displays, and biomedicines , owing to their outstanding visible light absorption , photoelectric conversion, adjustable energy level structure, and low energy consumption. Their exceptional properties, such as high visible light absorption, efficient photoelectric conversion, adjustable energy level structure, and low energy consumption, have attracted significant attention. However, the presence of ion migration in MHPs has been identified as a critical challenge, leading to reduced energy conversion efficiency and device instability. Overcoming this obstacle is crucial for the commercialization of perovskite-based technologies. In recent years, extensive research has been conducted to understand the conditions and mechanisms of ion migration in perovskite materials, as well as develop strategies to mitigate its adverse effects . This paper adopts a dialectical perspective on ion migration, with a specific focus on energy barriers. A comprehensive review is provided, covering the fundamental concepts and formation mechanisms of both irreversible unidirectional and reversible bidirectional ion migrations. This paper begins by presenting a detailed summary of the degradation processes caused by irreversible unidirectional ion migrations phenomena induced by external fields, including illumination, stress/strain, thermal and electrical fields. Understanding the underlying mechanisms of such degradation is essential to address the stability concerns associated with perovskite devices. Moreover, the overview of bidirectional reversible ion migration phenomena in perovskite is presented. The cyclic formation and restoration of Schottky barriers at the interface can significantly influence the photoelectrical properties and impact the overall performance of perovskite devices. Various strategies for regulating ion migrations under external fields are discussed, aiming to enhance device stability and performance. By understanding the energy landscape and migration pathways, researchers can develop effective strategies to control and optimize ion migrations, ultimately improving the photoelectric conversion performance of perovskite devices. This paper provides comprehensive analysis of ion migration in perovskite materials, addressing fundamental concepts, ion migration mechanisms, and strategies for regulating ion migrations. By providing a clear understanding of the challenges associated with ion migration, this work contributes to the advancement of perovskite-based technologies and facilitates their commercialization. Ultimately, the optimization of ion migration control will lead to improved performance and stability of perovskite devices, enabling their widespread adoption in various applications. The ion migration within perovskite structure include irreversible and reversible migrations and could be regulated through electrical field, light, strain/stress etc . Regulation of ion migration conducted on MHPs-based devices could achieve optimized photoelectric properties.