Strain–Phase Transition Interplay in Perovskites: Coupling Mechanisms and Regulation Strategy

Strain is a crucial factor determining the efficiency and stability of perovskite optoelectronic devices. Current research typically attributes the residual strain in perovskites to the thermal expansion that occurs during the annealing process due to the intrinsically weak chemical bonds and soft ionic lattice. Nevertheless, the stress–strain effects induced by phase transitions in perovskites, especially in 2D perovskites that are prone to multiple phase transitions, have been overlooked. In this Perspective, we propose that phase transitions induce significant changes in the lattice parameters and thermal expansion of perovskites, which in turn introduce considerable strain. By using advanced strain imaging techniques, revealing the interplay between strain and phase transitions in perovskites is crucial for obtaining high-performance and stable perovskite materials. Additionally, understanding the impacts of phase transition regulation on the crystallization, film formation, thermal expansion coefficient, and optoelectronic properties of perovskites is essential for enhancing the operational stability and performance of optoelectronic devices.