Near-Infrared Colloidal Manganese-Doped Quantum Dots: Photoluminescence Mechanism and Temperature Response

Doping in semiconductor quantum dots (QDs) is a promising approach for introducing unique properties compared to pure QDs. Although manganese (Mn) ion-doped wide band gap QDs have been widely studied, the optical properties of Mn-doped narrow band gap semiconductors are not well understood. Here, we report the synthesis of oil-soluble Mn-doped lead sulfide (PbS) QDs of identical size with different Mn contents. Compared to pure PbS QDs, the photoluminescence (PL) peak positions of Mn-doped PbS QDs exhibit a significant red-shift, resulting in a larger Stokes shift. The large Stokes shift of Mn-doped QDs is due to the electronic state of Mn ions, in which the photogenerated electron is transferred to the energy states of Mn ions and then recombined with holes. Mn-doped PbS QDs exhibit a faster temperature-dependent PL response compared to pure PbS QDs, demonstrating that the Mn-doped PbS QDs are promising alternatives for use as thermal sensors.