TiO₂ nanotubes decorated with ZnO rod-like nanostructures for efficient dye-sensitized solar cells

To increase the efficiency of TiO₂ nanotube-based dye-sensitized solar cells, we fabricated TiO₂ nanotubes and decorated them with ZnO rod-like nanostructures via anodization of Ti metal sheets followed by the hydrothermal growth of ZnO. Compared to conventionally anodized nanotubes, the modified nanotubes provided a higher specific surface area for dye adsorption. Besides increased dye adsorption, suppression of the recombination of photo-induced electrons at the electrode/electrolyte interface was observed in the modified nanotube-based systems because of the existence of a ZnO thin layer on the surface of nanotubes. This thin layer was applied as a seed for an oriented growth of ZnO. Dye-sensitized solar cells based on TiO₂ nanotubes decorated with ZnO rod-like nanostructures showed a higher power conversion efficiency of 3.84%, compared to standard nanotube devices with an efficiency of 2.06%.