Mixtures of ionic liquids were prepared and used for the development of composite redox electrolytes electrolytes by blending a standard low viscosity ionic liquid solvent (EMimDCA, 1-ethyl-3methylimidazolium dicyanamide) with various iodide-based ionic liquids based on the methylimidazolium cation (DMII, EMII, PMII, BMII and HMII). The novel electrolytes based on the [CnC1im]I/EMimDCA double salt ILs show interesting physicochemical properties including low viscosity (10-110 MPa s) and high diffusion coefficient of triiodides (DI3-, 5-10 ¿ 10-7 cm2/s), respectively, characteristics that promiss increased performance in DSC devices. Their electrochemical properties along with the conductivity were also tuned and optimized; values as high as and 2-4 mS/cm were estimated for the conductivity. Solar cells based on these composite electrolytes attained efficiencies over 4% under 1 sun with the highest being 5.5%, attained by EMimDCA-DMII mixture. Quite notably, these efficiencies further increased up to 6.5%, when the cells were illuminated by 0.1 sun.