TiO2 nanotube formation by Ti film anodization and their transport properties for dye-sensitized solar cells

In this paper, we present the synthesis of TiO2 nanotube (NT) arrays formed by anodization of Ti film deposited on a fluorine-doped tin oxide-coated glass substrate by direct current magnetron sputtering. NH4F/ethylene glycol electrolyte was used to demonstrate the growth of stable nanotubes at room temperature. TiO2 NTs as long as 4.8 ?m with the high expansion factor to the initial sputtered Ti film (2 ?m) were obtained, showing little undesired dissolution of the metal in the electrolyte during anodization. The average pore size and wall thickness of NTs were about 70 and 30 nm, respectively. Structural investigations on the transparent NT arrays reveal the presence of anatase phase after annealing. The NTs were sensitized by the N719 complex and the resultant photoelectrodes were incorporated into dye sensitized solar cells (DSSCs). The conversion efficiency of 1.97 % was obtained under AM 1.5 illumination and the open circuit voltage, short circuit current density and the fill factor were 0.59 V, 6.71 mA/cm2 and 0.50, respectively. Investigation of the electron transport of the DSSCs by electrochemical impedance spectroscopy showed that the electron diffusion length (8.6 ?m) was higher than NTs’ height. It was also observed that the electron transport resistance measured in NT DSSC was lower compared to the reported TiO2 nanoparticle one.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc