Enhanced photovoltaic performance of dye-sensitized solar cells using TiO2-decorated ZnO nanorod arrays grown on zinc foil

TiO2-decorated ZnO nanorod arrays directly grown on zinc foil are fabricated by a two-step approach combining hydrothermal oxidation and a sol–gel process for dye-sensitized solar cells (DSSCs) applications. Its dye absorption and light harvesting are increased by decoration with a TiO2 particle layer, resulting in enhancement of the photocurrent density. In addition, the open-circuit voltage (VOC) of the DSSCs is improved by suppressing interfacial carrier recombination. As a result, the conversion efficiency (η) of the TiO2-decorated ZnO photoanode is increased by a factor of 1.78 compared with that of the bare ZnO. The electrochemical impedance spectroscopy (EIS) analysis shows that depositing TiO2 particles on the surface of the ZnO nanorod arrays can effectively extend electron lifetime and decrease electron recombination rate.

► A novel dye sensitized solar cell which was made of vertically-aligned ZnO nanorods directly grown on Zn foils was fabricated through hydrothermal oxidation. ► The optimal efficiency is obtained from the effect of decorated TiO2 on the surface of ZnO nanorods using different cycle schedules for decorating. ► The decorated TiO2 affected the dye adsorption and light harvesting properties of the ZnO based-cells. ► Comparison with published data indicates that JSC is affected by light absorbance whereas VOC is more directly related to an energy barrier that suppresses the recombination rate. ► Electrochemical impedance spectroscopy (EIS) analysis shows that the interface charge recombination rate is reduced, and electron lifetime increases, in TiO2-decorated ZnO-based DSSCs.