Fig. 5. Flexible solar cells and mechanical stability.

a J–V curves of the flexible champion device measured under AM 1.5 G solar irradiation at 100 mW/cm² (inset: schematic diagram of flexible device architecture and PCE distribution of the flexible devices). b PCE of CsPbI₃ QD solar cell and CsPbI₂Br thin-film solar cell as a function of bending cycles (inset: photograph of the flexible QD solar cell). c Schematic diagram of the bending mechanical testing of QD and thin-film on a flexible substrate. d–g Top-view SEM images of the CsPbI₃ QD film, PbS QD film, CsPbI₂Br, and mixed perovskite thin-film fabricated on PET/ITO (2.5 × 2.5 cm) with mechanical bending (curvature radius of 0.75 cm), all films have a similar thickness between 300 and 400 nm.