A Supercooled Imidazolium Iodide Ionic Liquid as a Low-Viscosity Electrolyte for Dye-Sensitized Solar Cells

A series of allyl-functionalized imidazolium salts are reported, including 1-allyl-3-ethylimidazolium iodide and 1-allyl-3-propylimidazolium iodide, which have m.ps. close to room temp. and show typical properties of supercooled fluids if heated above their m.ps. Their viscosities in the liq. state are considerably lower than the benchmark ionic liq. used in solar cells, viz., 1-propyl-3-methylimidazolium iodide. Electrolytes contg. these new liqs. provide excellent efficiencies and good stability in dye-sensitized solar cells when subjected to an accelerated-light soaking test at 60 DegC. The structures of three of the new salts have been established in the solid state by single-crystal X-ray anal.