Effect of sulfur doped TiO₂ on photovoltaic properties of dye-sensitized solar cells

In a dye-sensitized solar cell (DSC), a nano-porous semiconductor layer plays an important role in the performance. It determines open-circuit voltage and it affects the dye adsorption capacity and charge transfer, which are closely associated with photocurrent and overall performance. TiO₂ is the most proper material for nano-porous layer since the first development of DSCs. This work focuses on the enhancement of TiO₂ by doping. Sulfur (S) doping enhances charge transfer and the photoconversion of TiO₂. Therefore, the increase in photocurrent and efficiency is expected by S doping. S is doped into TiO₂ by hydrolysis method. The amount of S is varied and their photo-responses are verified. The most effective S doped TiO₂ is applied to DSCs. Overall performance of DSC is enhanced by the addition of S doped TiO₂. Especially, the photocurrent is much increased by the improvement on charge transfer, electron lifetime, and photo-conversion. The photovoltaic properties of DSCs are investigated with various ratios of undoped and S doped TiO₂. Finally, a DSC based on undoped and S doped TiO₂ ratio of 1:1 has the highest efficiency, better than that of a standard DSC based on undoped TiO₂. [Figure not available: see fulltext.]