The effect of the addition of single and binary additives to a mixed solvent, ethylene carbonate+γ-butyrolactone, on the performance of dye-sensitized TiO2 solar cells (DSSCs) has been investigated. The addition of a single additive, 2-(dimethylamino)-pyridine, to the electrolyte containing an ionic salt, 1,2-dimethyl-3-propylimidazolium iodide, in the mixed solvent results in an enhancement of the cell performance. The performance of the cell has been further enhanced by the addition of the second additive, 5-chloro-1-ethyl-2-methylimidazole. The resulting DSSC has performed better than the one based on the conventional electrolyte in acetonitrile. The dependence of the stability of the cells on the temperature has been evaluated over the range of 30–120°C for outdoor applications.