Reduced graphene oxide modified TiO2 semiconductor materials for dye-sensitized solar cells

Abstract

Reduced graphene oxide (rGO) was prepared by reduction of graphene oxide (GO) under mild conditions and rGO/TiO₂ composite semiconductor materials were prepared by mixing rGO into TiO₂ paste and were used to deposit the photoanode films of dye sensitized solar cells (DSSCs). After preparation, the successful synthesis of rGO was confirmed using X-ray diffraction (XRD) and Raman spectroscopy analysis. The effect of rGO content on the performance of dye-sensitized solar cells was also investigated. After the addition of rGO, the photoanodes displayed enhanced dye adsorption properties with lower internal resistances, faster electron transport and lower charge recombination rate, which resulted in a high current density. At the optimum rGO concentration, the DSSC exhibited a J_sc of 15.23 mA cm⁻², a V_oc of 0.71 V, and a FF of 0.62 with the energy conversion efficiency (η) of 6.69%, indicating a increase in J_sc and η respectively with respect to that of a DSSC based on an unmodified TiO₂ photoanode, which gives a J_sc of 13.56 mA cm⁻², a V_oc of 0.70 V, and a FF of 0.63 with a η of 5.97%. However, the addition of excess rGO weakened the crystallization of particles on the surface of the photoelectrodes, which led to the enhancement of charge recombination, the reduction of dye adsorption and the decrease of photoelectric conversion efficiency of DSSCs. The rGO modified TiO₂ semiconductor materials could really enhance the efficiency of DSSCs after the optimal amount of rGO was successfully determined.