Ruthenium pyridine-derivative complexes are used in dye-sensitized solar cellTiO2 [DSSC] as a light to current conversion sensitizer. In order to improve the efficiency of the TiO2 DSSC the noble metal ruthenium and some compounds present in the electrolyte (consists of 0.6M of1-butyl-3 methylimidazolium iodide(BMII), 0.03M iodine, 0.06 M Lithium iodide 0.5 M 4-tetra-butylepyridine, 0.1 M guanidinium thiocynate). The geometries, electronic structures and optical absorption spectra of these compounds have been studied by using density functional theory (DFT) calculation at the B3LYP/LANL2DZ, B3LYP/GEN level of theory. All the geometric parameters are close to the experimental values. HOMOs are mainly on the electrolyte groups mixed with fewer characters of the metal atom, the LUMOs are mainly on the two pyridine ligands. This means that the electron transition is attributed to the absorption layer. The maximum absorptions of complexes are found to be at 400 nm for the compounds. This means that those compounds may be as a suitable sensitizer for solar energy conversion applications. The performance of the TiO2 DSSC solar cells have been confirmed with computer simulation using VASP.