A new ionic liquid S-propyltetrahydrothiophenium iodide (T(3)I) was developed as the solvent and iodide ion source in electrolyte for dye-sensitized solar cells. The electrochemical behavior of the I(3)(-)/I(-) redox couple and effect of additives in this ionic liquid system was tested and the results showed that this ionic liquid electrolyte revealed good conducting abilities and potential application for solar devices. The effects of LiI and dark-current inhibitors were investigated. The dye-sensitized solar cell with the electrolyte (0.1 mol L(-1) LiI, 0.35 mol L(-1) 12, 0.5 mol L(-1) NMBI in pure T(3)I) gave short-circuit photocurrent density (J(sc)) of 11.22 mA cm(2), open-circuit voltage (V(oc)) of 0.61 V, and fill factor (FE) of 0.51, corresponding to the photoelectric conversion efficiency (eta) of 3.51% under one Sun (AM 1.5). (C) 2009 Elsevier Ltd. All rights reserved.