Ultrafast Charge Transfer at a Quantum Dot/2D Materials Interface Probed by Second Harmonic Generation
journal contributionposted on 11.07.2018, 00:00 by Aaron J. Goodman, Nabeel S. Dahod, William A. Tisdale
Hybrid quantum dot (QD)/transition metal dichalcogenide (TMD) heterostructures are attractive components of next generation optoelectronic devices, which take advantage of the spectral tunability of QDs and the charge and exciton transport properties of TMDs. Here, we demonstrate tunable electronic coupling between CdSe QDs and monolayer WS2 using variable length alkanethiol ligands on the QD surface. Using femtosecond time-resolved second harmonic generation (SHG) microscopy, we show that electron transfer from photoexcited CdSe QDs to single-layer WS2 occurs on ultrafast (50 fs to 1 ps) time scales. Moreover, in the samples exhibiting the fastest charge transfer rates (≤50 fs) we observed oscillations in the time-domain signal corresponding to an acoustic phonon mode of the donor QD, which coherently modulates the SHG response of the underlying WS2 layer. These results reveal surprisingly strong electronic coupling at the QD/TMD interface and demonstrate the usefulness of time-resolved SHG for exploring ultrafast electronic-vibrational dynamics in TMD heterostructures.
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Second Harmonic Generation Hybrid quantum dot1 pslength alkanethiol ligandstime-domain signalQD surfaceultrafast electronic-vibrational dynamicsCdSe QDselectron transfergeneration optoelectronic devicesmonolayer WS 2Ultrafast Charge Transferphotoexcited CdSe QDstime scalesfemtosecond time-resolvedWS 2 layerphonon modeSHG responsesingle-layer WS 2donor QDexciton transport propertiesTMD heterostructurestime-resolved SHG