ZnO nanorods decorated graphene/ZnO nanoparticle composite as the counter electrode of dye-sensitised solar cells

Abstract

A counter electrode based on graphene, ZnO nanoparticles and ZnO nanorods was designed for dye-sensitized solar cells (DSSCs). In this counter electrode, a 200 nm thick composite film of graphene with ZnO nanoparticles served as the scaffolds while vertically aligned ZnO nanorods with the lengths of about 730 nm and the diameters of about 50 nm were employed to decorate these scaffolds. The surface morphology, crystal structure, photoluminescence of the graphene/ZnO composite counter electrodes were analysed by means of field-emission scanning electron microscope, X-ray diffractometer and photoluminescence spectroscopy, respectively. Under 1-Sun illumination (100 mW cm− 2, AM 1.5), J–V measurements were performed to characterise the photovoltaic performance of the DSSCs with the graphene/ZnO composite counter electrode. The power conversion efficiency of the DSSCs with the graphene/ZnO composite counter electrode was 0.17%, which was slightly higher than that of the DSSC with the Pt counter electrode (0.15%). The reasonable photovoltaic performance of the DSSCs can be attributed to the large surface area for the reduction of and direct pathway for electron transport from counter electrode to electrolyte. Our results have demonstrated that graphene/ZnO composite may be used as the low-cost counter electrodes for highly efficient DSSCs.