Synthesis of ZnO-decorated TiO2 nanotubes for dye-sensitized solar cells

Abstract

The effect of ZnO electrodeposition on the photovoltaic efficiency of dye-sensitized solar cells (DSSCs) with anodized TiO2 nanotubes followed by an annealing process was investigated. ZnO were introduced into anodized TiO2 nanotubes on Ti foil by electrodeposition in an aqueous electrolyte containing 10mM Zn(NO3)2 6H2O with different processing time, i.e. 25, 50, 100, and 200s. The surface morphologies and the crystallinity of the ZnO-decorated TiO2 nanotubes were inspected via scanning electron microscopy and transmission electron microscopy, respectively. The photovoltaic efficiencies of fabricated DSSCs were characterized by a solar cell measurement system. In addition, we evaluated the kinetics of the photoelectrochemical phenomena in DSSCs via electrochemical impedance spectroscopy with a focus on exploring the electron lifetime and internal resistance of the cells in a quantitative manner based on an equivalent circuit model. It was found that the photovoltaic efficiency of DSSCs with ZnO-decorated TiO2 nanotubes for 50s was improved by more than 60%, compared to DSSCs with as-prepared TiO2 nanotubes. This improvement is ascribed to increased dye loading and photocurrent density.