Reduced graphene oxide wrapped hierarchical TiO 2 nanorod composites for improved charge collection efficiency and carrier lifetime in dye sensitized solar cells

Abstract Three dimensional hierarchical TiO 2 nanorods-reduced graphene oxide (HTNs-rGO) composites with different rGO wt% were directly grown on conducting glass substrate by an in situ hydrothermal process for improved charge separation and collection in dye sensitized solar cells (DSSCs). The crystal structure and chemical composition of as grown composites were confirmed by X-ray diffraction and optical studies. Electron microscopic studies on the composites surface morphologies revealed the formation of rGO wrapped or intertwined HTNs architectures onto the FTO substrates with thicknesses ranging from 14.33 to 15.70 μm. 2 wt% rGO loaded HTNs composite photoanode showed a superior power conversion efficiency of 4.54% as compared to the other wt% rGO loaded HTNs composite and bare HTNs photoanodes in DSSCs. This is due to optimal loading of rGO facilitating formation of a better charge transport channel within HTNs matrix and reducing charge transport resistance (R tr ), which resulted in a higher charge collection of HTNs-rGO composite. Besides, the solar cell current-voltage (J-V) and electrochemical impedance characterizations confirmed the superior light scattering and dye loading capabilities of HTNs, together with a low charge transport resistance and improved charge carrier lifetime in HTNs-rGO composites contributed to the photovoltaic performance enhancement of their DSSCs.