Transparent conducting oxide glass grown with TiO2-nanotube array for dye-sensitized solar cell

An arc ion plating (AIP) deposition system was employed to produce metal titanium layer on transparent conducting oxide glass, and followed by anodically oxidizing to form a TiO2-nanotube array electrode. A dye-sensitized solar cell (DSC) was then assembled as ITO glass/[TiO2-nanotube (N3 dye)]/I2 + LiI electrolyte/Pt/ITO glass. Anodizing bath composition was varied, and post-annealing was carried out. Consequent changes in the TiO2-nanotube array microstructure and photovoltaic efficiency of the assembled DSC device were revealed. Experimental results show that a 5-μm thick metal titanium layer can be obtained after 45 min AIP deposition. The metal titanium layer underwent complete conversion into XRD-amorphous TiO2-nanotube array after anodic oxidation for 2 h. The tube can reach 10.7 μm long with tube inner diameter 92 nm. The ammonium fluoride in the anodizing bath accelerates the tube growth rate. Thermal annealing at temperatures over 250 °C works best on anatase crystallization of the TiO2-nanotube. An ultimate photovoltaic efficiency 1.88% (active area 1 cm2) of the assembled DSC device can be obtained for the TiO2-nanotube grown ITO glass annealed at 350 °C.