Preparation of ZnO-coated TiO 2 electrodes using dip coating and their applications in dye-sensitized solar cells

Abstract

This study investigates the applicability of a ZnO-coated TiO 2 working electrode in a dye-sensitized solar cell (DSSC). This working electrode was designed and fabricated by the following procedures: (1) two consecutive TiCl 4 treatments were performed when preparing the TiO 2 electrode, one prior to and the other following the spin printing of the TiO 2 colloid on a FTO-glass (Fluorine doped tin oxide, SnO 2:F) substrate; (2) a simple dip coating method was used to fabricate a ZnO-coated TiO 2 electrode by immersing a FTO-glass substrate with a TiO 2 film in a solution of zinc acetate dehydrate [Zn(CH 3COO) 2∙2H 2O] and ethanol. This working electrode was then immersed in a solution of N-719 (Ruthenium) dye at a temperature of 70 °C for a preset duration. Finally, the DSSC was assembled, and the short-circuit photocurrent, the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using an I–V measurement system. The effects of the concentration of Zn(CH 3COO) 2∙2H 2O, the duration of dipping, and the dye loading on the power conversion efficiency of a DSSC were also examined. Most importantly, this study shows that the power conversion efficiency of the DSSC with a ZnO-coated TiO 2 electrode (6.62%) substantially exceeds that of the conventional DSSC with a TiO 2 electrode (5.45%) due to the effects of a ZnO barrier and the TiCl 4 treatment.