Graphene nanosheet counter-electrodes for dye-sensitized solar cells

Graphene nanosheets (GNs) have been investigated as a counter electrode for dye-sensitized solar cells (DSCs). Mesoporous TiO₂ films are prepared from the commercial TiO₂ nano-powders by screen-printing technique on fluorine-doped tin oxide (FTO) slides. GNs are applied to substitute for platinum as counter-electrode materials. GN films are screen printed on FTO glass using a paste based on GNs dispersed in a mixture of terpineol and ethylcellulose. GN counter-electrodes were prepared by annealing the GN films at different temperatures. A metal-free organic dye (indoline dye D102) is used as a sensitizer. Morphological and electrochemical properties of the formed counter-electrodes are investigated by scanning electronic microscopy and electrochemical impedance spectroscopy (EIS), respectively. The electronic and ionic processes in platinum and GNs based DSCs are analysized and discussed. A conversion efficiency of 2.94 % has been obtained for GNs based DSCs. It is found that the quality of the GN counter-electrode and the photovoltaic performance are strongly affected by the annealing temperature of GN materials.