In‐Situ Polymerization Strategies for Flexible Perovskite Solar Cells: Mechanisms and Prospects

Abstract Flexible perovskite solar cells (FPSCs) possess great market competitiveness in the field of portable devices. However, internal defects and tensile stress will inevitably be introduced during the preparation and operation of FPSCs, the cracks and delamination will easily occur during practical operations such as bending and folding, which is adverse to the long‐term stability of devices. Polymers, as precursor additives containing various functional groups, are widely applied for crystallization regulation and flexibility enhancement of perovskite films. Benefiting from the remarkable achievements in residual stress release and stability improvement of perovskite, the strategies based on in‐situ polymerization are widely reported not only in rigid PSCs but also in FPSCs. Here, the in‐situ polymerization strategies for FPSCs are systematically summarized. First, the factors affecting the performance of FPSCs are discussed from defects, stress, and external environment. Then, the functions of polymers in PSCs are listed, including crystallization control, moisture resistance enhancement, and film toughening. Next, the mechanisms and advantages of in‐situ polymerization, the performance improvement of FPSCs by in‐situ polymerization additives are elaborated. Finally, the characteristics of in‐situ polymerization are summarized and the prospects for future development of FPSCs by in‐situ polymerization are concluded.