Sulfur-doped TiO2 nanocrystalline photoanodes for dye-sensitized solar cells

Sulfur-doped TiO2 is prepared by a mechanical process with ball milling the thiourea with commercial P25 TiO2 nanoparticles and successfully used as photoanode of dye-sensitized solar cells (DSSCs). The x-ray photoelectron spectroscopy results indicate that sulfur-doped TiO2 are locally distorted by incorporating S6+ species into TiO2 and substitutes for some of the lattice titanium (Ti4+); meanwhile, a clear reduction in the band gap energy of the sulfur-doped TiO2 photoanode compared to the band gap value for P25. The linear sweep voltammetry indicate that the edge of the conduction band of sulfur-doped TiO2 move positively toward the vacuum level. A conversion efficient of 6.91% was achieved for a DSSC based on sulfur-doped solar cell, which was 24% higher than that of the un-doped solar cell. The improved performance was ascribed to the improved charge injection from the dye to the sulfur doped TiO2 electrode, as evidence by an improved spectral response in the whole wavelength range.