Concave and Convex Bending Influenced Mechanical Stability in Flexible Perovskite Solar Cells

Flexible perovskite solar cells (F-PSCs) have shown great potential application towards future wearable power sources with increasing power conversion efficiency (PCE) and mechanical stability. In this study, we found that the mechanical stability of F-PSCs is also influenced by the way of mechanical bending. The F-PSCs exhibit better mechanical stability with concave bending as compared with the ones with convex bending. Further study based on J-V characteristics and impedance spectra indicate that the series resistance (R-s) of the device has a larger increase, which results in the degradation of photovoltaic performance after convex bending. Furthermore, it is revealed that the conductivity decrease of perovskite film is responsible for the increased R-s, consequently leads to poorer mechanical stability after convex bending. Our findings may attract the attention of developing the standard of characterizing mechanical stability in the flexible perovskite-based devices.