Preparation of ZnO-coated TiO2 electrodes using dip coating and their applications in dye-sensitized solar cells

This study investigates the applicability of a ZnO-coated TiO2 working electrode in a dye-sensitized solar cell (DSSC). This working electrode was designed and fabricated by the following procedures: (1) two consecutive TiCl4 treatments were performed when preparing the TiO2 electrode, one prior to and the other following the spin printing of the TiO2 colloid on a FTO-glass (Fluorine doped tin oxide, SnO2:F) substrate; (2) a simple dip coating method was used to fabricate a ZnO-coated TiO2 electrode by immersing a FTO-glass substrate with a TiO2 film in a solution of zinc acetate dehydrate [Zn(CH3COO)2∙2H2O] 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(CH3COO)2∙2H2O, 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 TiO2 electrode (6.62%) substantially exceeds that of the conventional DSSC with a TiO2 electrode (5.45%) due to the effects of a ZnO barrier and the TiCl4 treatment.

Graphical abstractThe power conversion efficiency of the DSSC with a ZnO-coated TiO2 electrode (6.62%), prepared by immersing a TiO2 electrode in a solution of Zn(CH3COO)2.2H2O and ethanol, substantially exceeds that of the conventional DSSC with a TiO2 electrode (5.45%) due to the effects of a ZnO barrier and the TiCl4 treatment.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A ZnO-coated TiO2 working electrode was applied to a DSSC. ► Effects of Zn(AC)2∙2H2O concentration, dipping time and dye loading were examined. ► DSSC with a ZnO-coated TiO2 had 6.62% efficiency due to ZnO barrier and TiCl4 treatment.