Long room-temperature valley lifetimes of localized excitons in MoS2 quantum dots

Transition metal dichalcogenides (TMDs), which exhibit valley polarization characteristics, are very promising materials for the realization of valleytronic devices. To implement practical applications, a long valley lifetime at room temperature is necessary. Here, we demonstrate that diethylenetriamine (DETA)-functionalized MoS2 quantum dots (QDs) exhibit long valley lifetimes for localized excitons at room temperature. Based on polarization-resolved photoluminescence (PL) dynamics, the degree of circular polarization of defect-bound localized excitons in MoS2 QDs are found to be between 21% and-22%. The observed room-temperature valley lifetimes for excitons in MoS2 QDs are more than 58 ns, much larger than those in MoS2 monolayers (<= 4 ps). The decay of polarization-resolved PL and the dynamical degree of circular polarization can be modeled by using a rate equation approach. This model is based on intervalley scattering in dark exciton states and relaxation from dark exciton states to localized exciton states. Such a long-lived valley lifetime at room temperature could be significant for future valleytronics applications.<br /> (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement