Lattice strain inhomogeneity in halide perovskite films: its origins and regulations

Since perovskite solar cells reached an astonishing power conversion efficiency of 27%, the persistent stability issue has received significant attention, paving the way for a major step up in commercialization. Strain control has been proposed as a promising technology to address the stability issue because defects governing the structural stability are susceptible to lattice strain. Accordingly, various strategies have been developed and found to be effective in terms of device stability. Nevertheless, most of them are based on interface management by varying target molecules at the interface without understanding the underlying fundamentals. In this review article, we thoroughly investigate the origins of lattice strain in perovskite films, ranging from the atomic scale to the bulk scale, and introduced effective approaches to resolve the strain issue by listing relevant materials. Finally, the synergistic effect of strain regulation is discussed to recognize the feasible impact from the perspective of device performance.