Reversible Structural Swell–Shrink and Recoverable Optical Properties in Hybrid Inorganic–Organic Perovskite

Ion migration in hybrid organic–inorganic perovskites has been suggested to be an important factor for many unusual behaviors in perovskite-based optoelectronics, such as current–voltage hysteresis, low-frequency giant dielectric response, and the switchable photovoltaic effect. However, the role played by ion migration in the photoelectric conversion process of perovskites is still unclear. In this work, we provide microscale insights into the influence of ion migration on the microstructure, stability, and light–matter interaction in perovskite micro/nanowires by using spatially resolved optical characterization techniques. We observed that ion migration, especially the migration of MA⁺ ions, will induce a reversible structural swell–shrink in perovskites and recoverably affect the reflective index, quantum efficiency, light-harvesting, and photoelectric properties. The maximum ion migration quantity in perovskites was as high as approximately 30%, resulting in lattice swell or shrink of approximately 4.4%. Meanwhile, the evidence shows that ion migration in perovskites could gradually accelerate the aging of perovskites because of lattice distortion in the reversible structural swell–shrink process. Knowledge regarding reversible structural swell–shrink and recoverable optical properties may shed light on the development of optoelectronic and converse piezoelectric devices based on perovskites.