Novel hydrophobic ionic liquids electrolyte based on cyclic sulfonium used in dye-sensitized solar cells

A novel series of hydrophobic room temperature ionic liquids based on six cyclic sulfonium cations were first time synthesized and applied in dye-sensitized solar cells as pure solvents for electrolyte system. The chronoamperograms result showed that the length of substituent on sulfonium cations could inhibit the I3- diffusion and the five-ring structure of sulfonium was benefit for fast triiodide ion diffusion. The electrochemical impendence spectra measurement of dye-sensitized solar cells with these ionic liquid electrolytes was carried out and the result indicated that the cations’ structure had indeed influence on the cells’ performance especially for the fill factor, which was further proved by the measurement result of I–V curves of these dye-sensitized solar cells. The conclusion was obtained that the electron exchange reaction on Pt counter electrode/electrolyte interface dominated the cells’ performance for these ionic liquid electrolyte-based DSCs.