Electrical and Optical Properties of Nickel- and Molybdenum-Doped Titanium Dioxide Nanoparticle: Improved Performance in Dye-Sensitized Solar Cells

Nanocrystalline undoped and doped TiO₂ particles with different concentrations of nickel and molybdenum (1-7%) was synthesized using the hydrothermal method followed by characterization using standard analytical techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis spectroscopy. The XRD analysis shows no change in crystal structure of TiO₂ after doping with different concentration of Ni and Mo which indicates the single phase polycrystalline material. The SEM analysis shows the partial crystalline nature of undoped and doped TiO₂ and TEM analysis shows the particle size were in the range of 7-11 nm for Ni and 9-13 nm for Mo-doped TiO₂. The electrical and photovoltaic properties of the undoped and newly synthesized Ni- and Mo-doped TiO₂ were studied. The a.c. analysis shows that the dielectric constant ε′ and dielectric loss tan δ decreases with increase in frequency and become independent at higher frequency ranges. The dielectric property decreases with increase in dopant concentration which provides the valuable information about conduction process. At low frequency, the mechanism of a.c. conductivity was found to be same as that of d.c. conduction. As the frequency increases, the magnitude of complex impedance decreases indicating the increase in a.c conductivity. It was observed that the impedance increases with the corresponding increase in the dopant concentration. Under simulated solar illumination with an optimum content of Ni and Mo involves in TiO₂, the amount of dye absorption increases resulting in the gradual increase in photovoltaic current and hence improvement in the cell efficiency of dye-sensitized solar cell (DSSC) from 6.23 to 6.72% and 6.23 to 7.16% by increasing the dopant concentration of Ni and Mo from 0 to 5%, respectively, was achieved.