We have developed a novel and efficient organic liquid electrolyte composed of 1-ethyl-3-methylimidazolium iodide, iodine (I-2), and acetonotrile solvent for a nanocrystalline TiO2 solar cell sensitized with a Ru(II) terpyridyl complex. A solar energy-to-electricity conversion efficiency of 8.0% was attained under AM 1.5 irradiation (100mWcm(-2)).