TiO₂ nanotube layers on Ti substrates for high efficiency flexible dye-sensitized solar cells

We report herein the promising application of TiO₂ nanotubes formed on a Ti substrate to a flexible dye-sensitized solar cell illuminated from the back-side. We found that anodization of a Ti substrate in an extremely dilute perchloric acid solution yielded the formation of a high aspect-ratio TiO₂ nanotube layer on the Ti substrate. The nanotube layer has the equivalent surface area for dye-adsorption to a TiO₂ nanoparticle layer. This novel one-dimensional TiO₂ material provided efficient carrier generation interfaces as well as an efficient transport pathway for the carriers, evidenced by the enhanced photocurrent and photovoltage of the cell.