A Comparative Investigation of Dye-Sensitized Titanium Dioxide (TiO2) Nanorods Grown on Indium Tin Oxide (ITO) Substrates by Direct and Seed-Mediated Hydrothermal Methods

We report a comparative investigation of the characteristics of modified TiO2 nanorods grown on conducting indium tin oxide glass (ITO) substrates by two different hydrothermal methods: the direct method by which rutile TiO2 nanorods were grown directly on plain ITO substrates and the seed-mediated one using which a thin film of anatase TiO2 seed layer was laid down by spin coating and annealing prior to the growth of TiO2 nanorods on it. Microstructural analysis of the samples using X-ray diffraction confirmed their rutile nature. The average crystallite size estimated using Scherrer's formula was found to fall in the range of 11-17 nm in both cases. Field emission scanning electron microscopy revealed the nanorod morphologies of a dandelion arrangement in the case of directly grown ones and a proper vertical orientation in the case of the seed-mediated method. UV-Vis spectroscopy analysis of both the samples exhibited redshifts with intense absorption of visible radiation, and the seed-mediated one was found to possess an increased bandgap. The transport nature of the samples was characterized by significant increase in both dark and photocurrents. The results show that the dark and photocurrent values of the directly grown TiO2 nanorods were greater than those of the seed-mediated ones by similar to seven and five folds, respectively, and therefore, it could serve as efficient photoelectrodes in dye-sensitized solar cells.