Strain Engineering Toward High‐Performance Formamidinium‐Based Perovskite Solar Cells

The power conversion efficiency (PCE) of organic–inorganic halide perovskite solar cells (PSCs) has increased rapidly in recent years, with the certified best perovskite single‐junction photovoltaics reaching an astounding PCE of 26%. Formamidine (FA)‐based perovskites possess excellent photovoltaic properties and superior thermal stability, establishing them as one of the most promising perovskite materials for light absorption. However, the issue of the phase instability of black‐phase formamidinium lead iodide ( α ‐FAPbI 3 ) perovskite has seriously impeded its commercialization process, with the strain found in perovskite films being regarded as a significant factor impacting the stability of PSCs. This article begins by examining the sources of strain and the characterization techniques related to perovskites. Subsequently, it outlines the effects of strain on FA‐based perovskites and presents strategies to modify lattice strain. Finally, the potential for strain engineering in the future is discussed. This review aims to clarify the impact of strain on FA‐based perovskite, determine potential methods of strain engineering to enhance device performance, and ultimately facilitate the commercialization of these materials.