Titania Nanotubes Decorated with Zn-Doped Titania Nanoparticles as the Photoanode Electrode of Dye-Sensitized Solar Cells

We decorated Zn-doped TiO₂-nanoparticle-based photoanodes with carbon nanotube (CNT)-derived TiO₂ nanotubes (TNs) to enhance the power conversion efficiency of dye-sensitized solar cells (DSCs). X-ray photoelectron spectroscopy analysis verified that Zn ions, in the range of 0 to 1 at %, were successfully doped into the TiO₂ lattice. Field-emission SEM and TEM images of the TNs, as derived from the sol–gel template-assisted route, revealed that a uniform TiO₂ coating with a thickness of 60 to 120 nm was deposited on the surface of the CNT template through a noncovalent route. We observed that the cell efficiency improved from 6.80 for pure TiO₂ to 7.52 for 0.75 at % Zn-doped TiO₂ nanoparticles due to a reduction in charge recombination and enhancement in electron injection, as confirmed by using photoluminescence spectroscopy. Further improvements in the efficiency of up to 8.47 % were achieved by the incorporation of 5 wt % TNs into the Zn-doped TiO₂ photoanodes, as a result of enhancements in electron transport and light scattering, which was verified by using diffuse reflectance spectroscopy.