Synergistic effect from an additive induces enhanced bending resistance and self-healing properties for efficient flexible perovskite solar cells

Although more than 20% efficiency have been obtained for flexible perovskite solar cells (FPSCs), there still needs more research to essentially enhance the bending resistance and self-healing characters for flexible devices. Here, an additive of trifluorobenzenesulfonamide (TFBSA) was added into perovskite, leading to much improved bending resistance and self-healing properties. The text results demonstrate that, with synergistic effect of Lewis base, high electronegative polarity C-F group and amide group in TFBSA, the defects and carrier recombination of FPSCs are significantly inhibited, thus an excellent photoelectric conversion efficiency of 19.29% from 16.44% is obtained, and the bending resistance and self-healing nature of FPSCs are greatly improved. It can maintain 82% of its efficiency after 3000 bending cycles, while efficiency of the control decreased to 11%. At the same time, modified devices demonstrate superior self-healing properties. It is found that modified FPSC recovered from 82% to 98% of its initial efficiency when it was placed in glove box in dark at room temperature for 7 days after 3000 bending cycles. While the control one only regained 19% from 11% at same conditions. Our work provides a new strategy for FPSCs to radically enhance self-healing properties and bending resistance by adding multifunctional group additives.