Effect of Ga doped TiO2 photoanode on photovoltaic performances of natural dye-sensitized solar cells

We investigated the electric performances of DSSCs (Dye Sensitized Solar Cells) using TiO₂ (Titanium dioxide) photoanodes doped with Gallium (Ga) for different concentrations (0.25, 0.5 and 1 mol %) and sensitized with a mixture natural dye (mallow with anthocyanin). The doped and undoped layers of photoanode were deposited with doctor blade method. The main properties like structure and optical absorbance of photoanodes doped with Ga were investigated. XRD spectra reveal that studied films exhibit tetragonal structure of anatase TiO₂ showing a small shift to the higher diffraction angle when the concentration of the Ga increases. The crystallites have an average size in the range of 23-28 nm. UV-Vis absorption revealed that Ga addition enhances the light absorption in the visible range by shifting the absorption of TiO₂ nanoparticles to visible region. The energy band gap of realized nanoparticles was decreased when the dopant concentration increases. It passes from 3.26 eV in pure TiO₂ to 3.06 eV for 0.5%Ga-TiO₂. The efficiency of realized DSSC was increased considerably compared to that using pure TiO₂ photoanode. The current versus voltage (I-V) characteristics reveal that the DSSCs prepared using Ga-TiO₂ layer have significantly improved parameters. In fact, the DSSC fabricated with 0.5%Ga-TiO₂ has a high power conversion efficiency of 0.3%, short current density of 2.12 mA/cm² and open circuit voltage of 0.45 V.