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 melting points close to room
temperature and show typical properties of supercooled fluids if
heated above their melting points. Their viscosities in the liquid
state are considerably lower than the benchmark ionic liquid used
in solar cells, viz., 1-propyl-3-methylimidazolium iodide. Electrolytes
containing these new liquids provide excellent efficiencies and good
stability in dye-sensitized solar cells when subjected to an
accelerated-light soaking test at 60 °C. The structures of three of
the new salts have been established in the solid state by single-crystal X-ray analysis.