Strain Control to Stabilize Perovskite Solar Cells

Perovskite solar cells (PSCs) are rivaling most commercial photovoltaics in the aspect of efficiency and cost, while their intrinsic instability remains a major concern for their practical deployment. The presence of undesirable strain in PSCs during device fabrication and operation refers to the extension/narrowing of chemical bonds and expansion/shrinkage of lattice volume, which largely affects device stability due to promoted phase transition, chemical decomposition, and mechanical fragility. Pioneering investigations and remarkable achievements have revealed that strain control is indispensable in the design of stable PSCs. Herein, the evolution of strain in perovskite thin films and its effect on device performance is elucidated, and state‐of‐the‐art strategies of strain modulation are systematically reviewed. A thorough understanding and cautious control of the strain‐related phenomenon pave the pathway to derive perovskite materials with desired properties. Non‐uniformly distributed tensile strain is likely to present in solution‐processed perovskite thin films, which severely undermines the operational stability of resultant perovskite solar cells. A fundamental understanding and cautious control of residual strain within the perovskites is indispensable to derive stable perovskite materials with designed properties.