The design of Mn²⁺&Co²⁺ co-doped CdTe quantum dot sensitized solar cells with much higher efficiency

High quality Mn²⁺-doped CdTe quantum dots (QDs), Co²⁺-doped CdTe QDs and Mn²⁺&Co²⁺ co-doped CdTe QDs were successfully synthesized via an aqueous phase method with mercaptopropanoic acid (MPA) ligands. The doped QDs maintain the same zinc blende structure of CdTe by X-ray diffraction (XRD). The Mn²⁺-doped CdTe QDs and Co²⁺-doped CdTe QDs both show a red-shift on absorption and photoluminescence (PL) spectra compared to pure CdTe QDs. In addition, Mn²⁺-doped CdTe QDs show a significant increase in the PL lifetime due to an orbitally forbidden d-d transition, which is of benefit to the reduction of electron recombination loss. Co²⁺ doping has a more matched doping energy level. In view of this, Mn²⁺&Co²⁺ co-doped CdTe QDs were applied as sensitizers for quantum dot sensitized solar cells, resulting in a significantly enhanced efficiency.