Mechanically and operationally stable flexible inverted perovskite solar cells with 20.32% efficiency by a simple oligomer cross-linking method.

Due to their great potential in wearable and portable electronics, flexible perovskite solar cells (FPSCs) have been extensively studied. The major challenges in the practical applications of FPSCs are efficiency, operational stability, and mechanical stability. Herein, we developed a facile approach by incorporating a cross-linking oligomer of trimethylolpropane ethoxylate triacrylate (TET) into perovskite films to simultaneously enhance the power conversion efficiency (PCE) and stability of FPSCs. A PCE of 20.32% was achieved, which are among the best results for the inverted FPSCs. Both mechanical and environmental stabilities were improved for the TET-incorporated FPSCs. In particular, the PCE retained approximately 87% of its initial value after 20,000 bending cycles at a radius of 4 mm. The inverted FPSCs retained 85% of the initial PCE after 500 h storage at 85 °C and 90% after 900 h continuous one-sun illumination. A joint experiment-theory analysis ascribed the underlying mechanism to the reduced defect densities, improved crystallinity, and stability of the perovskite absorbers on flexible substrates caused by TET incorporation.