Unexpected efficiency enhancement of flexible dye-sensitized solar cells by repeated outward bending

Abstract

The photovoltaic performance of flexible dye-sensitized solar cells (DSCs) is generally degraded during bending activity which presents a typical flexible service condition. In this study, however, we report an unexpected efficiency enhancement of ca. 19% (i.e., from 3.88% to 4.62%) of flexible DSCs after repeated outward bending. The photovoltaic performance, electrochemical properties, mechanical properties and electrical properties were examined to understand the efficiency enhancement mechanism. It was found that the anisotropic evolution of particle–particle connection in the nanostructured TiO₂ film, strengthening the electron transport in the out-plane (vertical to the TiO₂ film surface) direction and weakening the electron transport in the in-plane (parallel to the TiO₂ film surface) direction, is responsible for such an abnormal efficiency enhancement. Based on the results, an efficiency enhancement model for the flexible DSCs under repeated outward bending is proposed.