Electrophoretically Deposited TiO2 Nanotube Light-Scattering Layers of Dye-Sensitized Solar Cells

We report herein the enhanced light-to-electricity conversion efficiency of a dye-sensitized solar cell using a new bilayer structure of the TiO2 electrode. The bilayer structure consists of a light-absorbing TiO2 nanoparticle layer together with a light-scattering TiO2 nanotube layer formed upon. High aspect-ratio TiO2 nanotubes (alpha-TNTs) with a diameter of 20 nm were prepared via anodization of a Ti sheet in a perchloric acid solution, and the alpha-TNT layer was electrophoretically deposited onto the sintered TiO2 nanoparticle layer. The light-scattering property of the alpha-TNT layer was comparable to that of the commonly used TiO2 sub-micron nanoparticle layer. The alpha-TNT layer provided a large surface area for dye-adsorption as well as an efficient transport pathway for photo-generated carriers. These effects allowed a hilgher incident photon-to-current efficiency of the bilayer TiO2 structure with the nanotube light-scattering layer over the whole spectral range relative to that with a sub-micron nanoparticle layer.