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 TiO ₂ electrode. The bilayer structure consists of a light-absorbing TiO₂ nanoparticle layer together with a light-scattering TiO ₂ nanotube layer formed upon. High aspect-ratio TiO₂ nanotubes (α-TNTs) with a diameter of 20 nm were prepared via anodization of a Ti sheet in a perchloric acid solution, and the α-TNT layer was electrophoretically deposited onto the sintered TiO₂ nanoparticle layer. The light-scattering property of the α-TNT layer was comparable to that of the commonly used TiO₂ sub-micron nanoparticle layer. The α-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 higher 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.