Controlled synthesis of monodispersed ZnO nanospindle decorated TiO2 mesospheres for enhanced charge transport in dye-sensitized solar cells

Abstract

Dye-sensitized solar cells (DSSCs) have undergone extensive research and development to improve the device performance for commercial applications and for indoor applications in particular. Currently, titanium dioxide (TiO₂) is a key photoanode candidate for DSSC device assemblies. However, the high recombination rate at the interface and low electron mobility of TiO₂ remain very challenging disadvantages in devices using stand-alone TiO₂ structures as the photoanode. Herein, we report a new scheme consisting of ZnO nanospindles decorated on TiO₂ mesospheres as a long-term stable photoanode and explore the photon-induced charge carrier migration/transfer kinetics. Different proportions of ZnO spindles (0.05%, 0.10%, 0.15%, 0.20%, and 0.25%) decorated on the mesosphere TiO₂ were effectively synthesised using a simple solvothermal method and the resulting composites were explored as photoanodes in DSSCs. DSSC devices composed of TiO₂/ZnO nanocomposites demonstrated improved photovoltaic characteristics at different temperatures as well as exhibiting long-term durability. Regarding photovoltaic performance, the DSSC device with the TZC-0.05 photoanode offered an excellent power conversion efficiency (PCE) of 5.26% and an open circuit voltage V_OC of (0.75 V). Furthermore, a long-term stability test of the TZC-0.05 based DSSC device exhibited only a slight drop in the PCE as well as showing stable V_OC and FF performance. The best performing DSSC device (TZC-0.05) was studied at various temperatures from 30 to 55 °C, and the best response was exhibited at 35 °C, which is nearly equal to room temperature conditions.