Xue-Long He

Behavioral study of flexible platinum counter electrodes under alternative bending conditions

The electrocatalytic behavior of flexible platinum (Pt) counter electrodes (CEs) is of great importance to practical applications of flexible dye-sensitized solar cells (DSCs). In this study, the electrocatalytic activity of two different flexible Pt CEs with continuous and non-continuous Pt films, which were prepared by a sputtering method and an electroless deposition method, respectively, was studied under alternative bending conditions. The data obtained from electrochemical impedance spectroscopy measurements show that the electrocatalytic activity of the continuous Pt CEs slightly increases with the increasing bending cycles, due to the enhanced bare surface area formed from localized delamination and cracking. In contrast, the non-continuous Pt CEs demonstrate much higher resistance towards bending tests, i.e., their electrocatalytic activity remains unchanged even after 25000 bending cycles. This can be attributed to the high strain tolerance and unique surface structure for this kind of non-continuous Pt CE, which helps the release of stress during the bending tests.

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

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.