Fabrication of TiO₂ nanotube-nanocube array composite electrode for dye-sensitized solar cells

One dimensional TiO₂ nanotube structure recently plays an important role in the application of dye sensitized solar cells (DSSCs) due to its faster electron transport. The fabrication of photoanode using the TiO ₂ nanotube structures mixed with the TiO₂ nanoparticles was investigated to enhance the photovoltaic efficiency of DSSCs by increasing the surface area of electrode. In this work, self-organized and vertically-oriented TiO₂ nanotube arrays (TNAs) covered with uniformly distributed TiO₂ nanocubes (TNCs) were fabricated in a simple one-step anodization process. The X-ray diffraction patterns reveal that both TNAs and TNCs are in anatase phase. The scanning electron microscopy analysis demonstrates that the wall thickness and inner diameter of hexagonal close-packed TiO₂ nanotubes from chemically polished Ti foils are 10-15 and 100-120 nm, respectively, and the particle size of TNCs is 60-75 nm. The DSSC fabricated by the mixed morphological TNAs with TNCs shows an enhanced photoconversion efficiency of ∼ 63% than that of TNAs alone, due to the increase of both dye adsorption and electron transportation rate.