Synthesis of long TiO2 nanotube arrays with a small diameter for efficient dye-sensitized solar cells

Abstract

The surface/volume ratio of TiO2 nanotube arrays determines their electrical, optical and chemical properties for various applications. For dye-sensitized solar cells (DSSCs), it is very important to fabricate long TiO2 nanotube arrays with a larger surface area in order to have more dye loading and achieve higher conversion efficiencies accordingly. In this paper, a convenient anodization method is introduced to synthesize high aspect ratio TiO2 nanotubes at a low voltage and a high temperature. With a high reaction temperature, the diffusion rate of ions in the anodization process was enhanced. At the optimum temperature, nanotubes longer than 16 μm with outside diameters as small as 75 nm could be obtained at a voltage of 20 V. Significantly, using these resulting TiO2 nanotube arrays to fabricate front-side illuminated DSSCs, a conversion efficiency as high as 5.98% could be achieved due to the large surface area and the enhanced attachment of the dye.