The performance of dye-sensitized solar cells (DSSC) based on the propyl-methyl-imidazolium iodide (PMII) ionic liquid (IL) with and without the addition of SiO2 nanoparticles is studied. Results confirm that the presence of SiO2 nanoparticles in PMII electrolyte improves the charge transport of iodide/tri-iodide redox couple in the electrolyte and consequently increases the efficiency of DSSC up to 20%, relatively. Short circuit current density (J(SC)) of the DSSC under illumination may be limited by the charge transport of the redox couple in the IL-based electrolytes and a theoretical maximum of J(SC) can be evaluated from the cyclic voltammetry measurements of simple symmetric cells (TCO-Pt//electrolyte//Pt-TCO). The results show a strong temperature dependence of the DSSC performance if the PMII/I-2-based electrolytes are used. (C) 2007 Elsevier B.V. All rights reserved.