The effects of Mn2+ ions on the physical, chemical, and photovoltaic properties of the QDSCs are investigated. The Mn2+ ions doped into QDs can increase the light harvesting to produce more excitons. In addition, the Mn2+ dopant also raises the conduction band of CdSe, accelerates the electron injection kinetics and reduces the charge recombination, improving the charge transfer and collection. The increase of the efficiencies of light-harvesting, charge-transfer and charge-collection results in the improvement of the quantum efficiency of the solar cells