An investigation on the photoelectrochemical properties of dye-sensitized solar cells based on graphene-TiO₂ composite photoanodes

The graphene-TiO₂ nanocomposite has been prepared by mixing graphene oxide (GO) and tetra-n-butyl titanate (TBT) followed by the facile hydrothermal process when the reduction of GO to reduced graphene oxide (RGO) and the hydrolysis of TBT to TiO₂ happen. Characterization of the graphene-TiO₂ nanostructures is investigated in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. A dye-sensitized solar cell (DSSC) based on graphene-TiO₂ composite photoelectrode exhibits a high energy conversion efficiency of 4.28%, compared with a DSSC based on pure TiO ₂ photoelectrode (3.11%), accompanied by an increment in both short-circuit photocurrent density and open-circuit voltage. The significant enhancement in performance of DSSC is investigated through intensity-modulated photovoltage spectroscopy, intensity-modulated photocurrent spectroscopy, and electrochemical impedance spectroscopy. It is found that the incorporation of two-dimensional graphene nanosheets in the TiO₂ electrodes is the key factor leading to the improved photogenerated electron transfer ability and reduced charge recombination.