Modulating Internal Residual Stress for Efficient and Durable Flexible Perovskite Solar Cells

Flexible perovskite solar cells (F‐PSCs) are promising due to their low cost and versatility. However, the thermal instability of flexible substrates often results in internal defects and residual stress during the formation of perovskite films. To address this issue, cellulose diacetate (CDA), a green and eco‐friendly material derived from natural plant fibers, is used. CDA not only enhanced the quality of the perovskite films but also reduced the generation of internal residual stress. Furthermore, it effectively passivates defects that arise during the annealing process. As a result, a power conversion efficiency of 24.68% on flexible substrate, which is one of the highest values in the F‐PSCs, is achieved. The incorporation of CDA also lead to a more uniform stress distribution in the films during bending, significantly improving the long‐term environmental stability of the flexible devices. This sustainable fiber‐based approach provides a new direction for the advancement of flexible solar cells.