Flexible perovskite solar cells (F-PSCs) are highly promising for both stationary and mobile applications because of their advantageous features, including mechanical flexibility, their lightweight and thin nature, and cost-effectiveness. However, a number of drawbacks, such as mechanical instability, make their practical application difficult. Here, self-welding dynamic diselenide that is triggered by visible light into the structure of F-PSCs to improve their long-term stability by repairing cracks and defects in the absorber layer is incorporated. The diselenide confers the flexibility and self-welding properties to the Cs0.05MA0.05FA0.9PbI3 perovskite layer, enabling optimized F-PSC devices to achieve a power conversion efficiency of 24.85% while retaining ca. 92% of their initial efficiency after undergoing 15 000 bending cycles at a curvature radius of 3 mm. The corresponding flexible large-scale module with an active area of 15.82 cm2 achieved a record PCE of 21.65%.