Structural modification of TiO2 nanorod films with an influence on the photovoltaic efficiency of a dye-sensitized solar cell (DSSC)

TiO2 nanorod films have been deposited on ITO substrates by dc reactive magnetron sputtering technique. The structures of these nanorod films were modified by the variation of the oxygen pressure during the sputtering process. Although all these TiO2 nanorod films deposited at different oxygen pressures show an anatase structure, the orientation of the nanorod films varies with the oxygen pressure. Only a very weak (101) diffraction peak can be observed for the TiO2 nanorod film prepared at low oxygen pressure. However, as the oxygen pressure is increased, the (220) diffraction peak appears and the intensity of this diffraction peak is increased with the oxygen pressure. The results of the SEM show that these TiO2 nanorods are perpendicular to the ITO substrate. At low oxygen pressure, these sputtered TiO2 nanorods stick together and have a dense structure. As the oxygen pressure is increased, these sputtered TiO2 nanorods get separated gradually and have a porous structure. The optical transmittance of these TiO2 nanorod films has been measured and then fitted by OJL model. The porosities of the TiO2 nanorod films have been calculated. The TiO2 nanorod film prepared at high oxygen pressure shows a high porosity. The dye-sensitized solar cells (DSSCs) have been assembled using these TiO2 nanorod films prepared at different oxygen pressures as photoelectrode. The optimum performance was achieved for the DSSC using the TiO2 nanorod film with the highest (220) diffraction peak and the highest porosity

Effect of annealing temperature on TiO2 nanorod films prepared by dc reactive magnetron sputtering for dye-sensitized solar cells

The anatase TiO2 nanorod films have been prepared on ITO coated glass substrates at room temperature by dc reactive magnetron sputtering technique. The nanorods are highly ordered and are perpendicular to the substrate. XRD measurements show that the anatase nanorods have a preferred orientation along the [110] direction. The prepared nanorods were annealed at different temperatures (200 ºC – 500 ºC) in air for 1 hour. The dye-sensitized solar cells (DSSC) have been made using the as-deposited and annealed TiO2 nanorods as working electrode. It has been found that annealing will improve the efficiency of the DSSC. An optimum conversion efficiency of 2.13%, at 100 mW/cm2 light intensity, has been achieved with TiO2 nanorods annealed at 300 ºC

Searching for the Formation of Ti-B Bonds in B-Doped TiO2-Rutile

Surface B-doped TiO2-rutile (110) single crystals obtained through different approaches have been characterized by X-ray photoelectron spectroscopy (XPS), and their thermal stability investigated. The thermal decomposition of dimethylaminoborane on the clean TiO2(110) surface, both stoichiometric and understoichiometric (Ar+ sputtered), leads to a complete B oxidation to B2O3, which segregates from the TiO2. B-ion implantation (using B2H6 as a source) has allowed us to obtain both B2O3 and interstitial B doping, which is stable at high temperature. Two further methods were developed to deposit B in a titanium-rich surface, either by reactive Ti evaporation in B2H6 or by dosing B2H6 on a thin Ti overlayer. In both cases, Ti-B bonds were formed, due to the creation of substitutional B and boride-like compounds, but after a thermal treatment, they converted into B-O bonds, demonstrating that, in all cases, the system tends to evolve to the most stable species (B2O3). The reported XPS data represent useful benchmarks to characterize B-doped titania materials