Hydrophilic SiO2 nanoparticles in a binary ionic liquid (bi-IL) consisting of 1-propyl-3-methylimidazolium iodide (PMII) and 1-ethyl-3-methyl-imidazolium dicyanimide (EMIDCA) facilitated electron transfer and solidified the electrolyte for a dye-sensitized solar cell (DSC). We investigated the dependence of charge transport and photovoltaic performance on the composition of bi-IL electrolytes with varied ratio of SiO2 nanoparticles. The electrochemical impedance spectra revealed a decreased resistance to charge transfer at the Pt counter electrode (R-ct1) when SiO2 (up to 2.0 wt.%) was added, improving the photovoltaic parameters. The DSC based on a TiO2 nanocrystalline film (thickness 14.2 mu m) with a composite ionic gel electrolyte of EMIDCA/ PMII bi-IL (33 vol.% of EMIDCA) incorporating SiO2 (2 wt.%) exhibited a power conversion efficiency of 5.28% under simulated solar illumination (AM 1.5 G, 100 mW cm(-2)). The durability of DSC with a SiO2 solidified electrolyte was superior to that of a liquid one, exhibiting good stability at 60 degrees C in darkness during an accelerated test for 1000 h. (C) 2012 Elsevier B.V. All rights reserved.