For the first time, the application of a molten salt, triethylamine hydroiodide (THI), as a supporting electrolyte was investigated for the dye-sensitized solar cells (DSSCs). Titanium dioxide (TiO2) electrode was modified by incorporation of high- and low-molecular weight poly(ethylene glycol) along with TiO2 nanoparticles of two different sizes (300 nm (30 wt%) and 20 nm (70 wt%)). The highest apparent diffusion coefficient (D) of 8.12 x 10(-6) cm(2) s- I was obtained for I- (0.5 M of THI) from linear sweep voltammetry (LSV). Short-circuit current density (J(sc),) increases with the concentration of THI whereas open-circuit potential (V-oc remains the same. Optimum J(sc) (19.28 mA cm(-2)) and V-infinity (0.7 V) with a highest conversion efficiency (eta) of 8.45% were obtained for the DSSC containing 0.5 M of THI/ 0.05 M I-2/0.5 M TBP in CH3CN. It is also observed that the J(sc) and eta of the DSSC mainly relates with the D values of I- and charge-transfer resistances such as R-ctl and R-ct2 operating along Pt/TiO2 electrolyte interface, obtained from LSV and electrochemical impedance spectroscopy (EIS). For comparison, tetraethylammonium iodide (TEAI) and LiI were also selected as supporting electrolytes. Though both the THI and TEAI have similar structures, replacement of one methyl group by hydrogen improves the efficiency of the DSSC containing the former electrolyte. Further, the DSSC containing THI exhibits higher J(sc) and eta than LiI (7.70%), from which it is concluded that THI may be used as an efficient and alternative candidate to replace LiI in the current research of DSSCs. (c) 2007 Elsevier B.V. All rights reserved.