Ionic liquids (ILs) have been introduced as the electrolyte in dye-sensitized solar cells (DSSC) to replace organic solvents due to their non-flammability, chemical, and thermal stability, as well as less prone to evaporation and leakage. A series of eutectic ILs mixtures composed of 1-ethyl-3-methylimidazolium iodide, C2C1imI, 1-ethylpyridinium iodide C2pyI, 1-propylpyridinium iodide, C3pyI and 1-butylpyridinium iodide, C4pyI was developed. The structures and purity of the compounds were validated by nuclear magnetic resonance and Karl Fischer Titration. Their physicochemical properties, such as viscosities and ionic conductivities were evaluated for their potential use as electrolytes in DSSCs. The melting temperature of pure ionic liquids and the mixtures were determined using differential scanning calorimetry in the temperature range of 123.15 K to 393.15 K. It is found that eutectic mixtures were formed at the molar ratios of 0.75C2py]I:0.25C2C1im, {0.25C2pyI:0.75C2C1imI}, {0.50C2pyI:0.50C2C1imI}, 0.25C2C1im]I:0.75 C4pyI, 0.75C2C1imI:0.25C4pyI, and {0.50C2C1imI:0.50C4pyI} with the latter forming a highly stable liquid with no apparent melting peak in the studied temperature range. To understand the formation of eutectic composition, a correlation between molecular structures and the interaction energies of the cations and anions of ILs was performed using the Conductor-like Screening Model for Real Solvents (COSMO-RS). Dynamic viscosities of the binary mixtures were evaluated in the temperature range of 283.15 K to 353.15 K with 10 K increment. The highest ionic conductivity was exhibited by the eutectic ILs electrolyte {0.50C2C1imI:0.50C4pyI:I2(50 wt%)} at 9.67 mS·cm�1 showing its potential for electrolyte application in DSSC. © 2020 Elsevier B.V.