Plight of Mn Doping in Colloidal CdS Quantum Dots To Boost the Efficiency of Solar Cells

One of the strategies to boost the efficiency of highly promising yet struggling quantum dot solar cells (QDSCs) is to dope the QDs with optically active Mn2+ ions to create long-lived charge carriers and reduce the electron-hole recombination. The in situ deposition of QDs. although offers good surface coverage and better charge separation; in doped QDSCs the type of doping responsible for higher efficiencies cannot be ascertained. In the electrophoretically deposited Mn:CdS QDSCs, highest lattice doping of Mn2+ ions in presynthesized colloidal CdS QDs results in the highest efficiency, whereas exchange coupled Mn2+-Mn2+ pairs increase nonradiative electron-hole recombination and decrease the efficiency of QDSCs. With Mn:Cd at. % of 1.44, the efficiency could be increased to 2.1% as compared to 1.3% for CdS QDSC. The increase in efficiency by 66.4% is due to slower charge recombination in the photoanode and the electrolyte interface and higher electron lifetime in the doped QDSCs.