To make Quantum Dot Sensitized Solar Cells (QDSC) competitive, it is necessary to achieve power conversion efficiencies comparable to other emerging solar cell technologies. By employing Mn2+ doping of CdS, we have now succeeded in significantly improving QDSC performance. QDSC constructed with Mn-doped-CdS/CdSe deposited on mesoscopic TiO2 film as photoanode, Cu2S/Graphene Oxide composite electrode, and sulfide/polysulfide electrolyte deliver power conversion efficiency of 5.4%.