An Increase in Conversion Efficiency of Dye-Sensitized Solar Cells using Bamboo-Type TiO2 Nanotube Arrays

Abstract Highly ordered, bamboo type TiO 2 nanotube (NT) arrays were prepared by anodization of Ti foils in an electrolyte of 0.5 wt% NH 4 F in ethylene glycol using square-wave voltage. The morphology of obtained arrays consisting of closely packed TiO 2 NTs with inner diameter of 90 nm, wall thickness of 20 nm and length of 26 μm was characterized by scanning electron microscopy (SEM). Poly-crystalline anatase structure with crystallites of 28 nm in average size was determined by X-ray diffraction (XRD). Intensity-modulated photocurrent spectroscopy (IMPS) was employed to study the electron transport properties of TiO 2 NT arrays used in dye-sensitized solar cells (DSSCs). Dye molecules were found to cover both the inner and outer surface of the bamboo type TiO 2 NT arrays. Electrochemical impedance spectroscopy (EIS) showed reduced interfacial resistance and increased interfacial capacitance for the bamboo type TiO 2 NT arrays compared with the smooth type arrays, indicating an increase in surface area of the bamboo type TiO 2 NT arrays, which resulted in the higher dye loading. An increased conversion efficiency of 7.36% was achieved for the DSSCs based on the bamboo type TiO 2 NT arrays attributing to the significant increase of dye loading resulted from the bamboo structure.