Quantum dot sensitized solar cells (QDSSCs) require special electrolytes, which are not always compatible with the requirements of dye sensitized solar cells. CdS and PbS quantum dot sensitized solar cells are able to show promising power conversion efficiencies in the presence of an organic thiolate/disulfide redox electrolyte. Also, an appreciable enhancement in performance is noticed when such devices are co-sensitized with a Ru-dye. The measured cell efficiencies of the CdS/dye and PbS/dye co-sensitized solar cells are 3.93% and 4.18%, respectively, which are higher than the sum of the corresponding individual QDSSCs and the dye sensitized solar cell (DSSCs). The enhancement seen with co-sensitization was investigated and explained by the fact that it suppressed back electron transfer processes in the cell, which was ascertained by electrochemical impedance spectroscopy (EIS) results. (C) 2014 Elsevier B.V. All rights reserved.