Two organic redox couples: tetrabutylammonium cation (McMT-TBA+)/disulfide dimer (BMT) and tetramethylammonium cation (McMT-TMA+)/BMT derived from 2-mercapto-5-methyl-1, 3, 4-thiadiazole (McMT) were introduced to the CdS quantum dots sensitized solar cells (QDSCs), compared with the one based on the inorganic sulfide electrolyte (Na2S/S).It was found that the charge transfer resistances at the interface of the organic sulfide electrolytes and the platinum counter electrode are much lower and the interface reaction rates are higher.