Six kinds of binary ionic liquid electrolytes were used for DSC and the photoelectric conversion efficiency (PCE) of the device varies from 1.39% to 4.98%. Among these ionic liquids, the electrolyte composed of 1-butyl-3-methylimidazolium iodide (BMII) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) reached the highest efficiency. In order to optimize this binary ionic liquids electrolytes, Electrochemical impendence spectroscopy (EIS), UV-Vis spectroscopy, and photovoltaic performance of DSC based on BMII and EMIMBF4 with the different concentration of iodine were performed. The results showed that the Pt-electrolyte charge-transfer resistance (RPT) , the TiO2-electrolyte charge-transfer resistance (RcT)and Warburg impedance (Zw) decreased with the iodine concentration increasing, however, the absorption intensity of the electrolytes increased. When the concentration of iodine was 0.25 mol/L, the highest PCE of 5.20% was obtained for the DSC based on the binary BMII/EMIMBF4 ionic liquid electrolyte under AM1.5.