Efficient ZnO-based counter electrodes for dye-sensitized solar cells

ZnO is usually exploited as a photoelectrode for dye-sensitized solar cells (DSSCs), but it has not been applied as a DSSC counter electrode. Herein, it is reported that ZnO with poly(3,4-ethylene-dioxythiophene): polystyrene sulfonate (PEDOT:PSS) could be an efficient DSSC counter electrode with a maximum power conversion efficiency of 8.17%. Furthermore, it was found that the conversion efficiency of DSSCs with the ZnO/PEDOT:PSS counter electrode strongly depends on the ZnO content. Density functional theory (DFT) calculations, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements revealed that the variation of the conversion efficiency with ZnO content is determined by the fill factor (FF), which is dependent on the combination of the catalytic activity of ZnO and the conductivity of PEDOT:PSS.