Geiregat, Pieter

Hens, Zeger

Schiettecatte, Pieter

Ghent University Academic Bibliography

AcknowledgementsUltrafast Carrier Dynamics in Few-Layer Colloidal Molybdenum Disulfide Probed by Broadband Transient Absorption SpectroscopyPieter Schiettecatte,1,2 Pieter Geiregat,1,2 Zeger Hens1,2This research project has been funded by FWO-Vlaanderen.Introduction1 Physics and Chemistry of Nanostructures, Ghent University, Belgium 2 Center for Nano and Biophotonics, Ghent University, Belgium1120nanosheets (TEM)bottom-up synthesis of MoS2T = 320°COLAN2MoCl5/OACS2/OLAColloidal Synthesis of Molybdenum DisulfideInsights into the photophysics of TMDs made by exfoliation or CVD have been pivotal for the advancementtoward a broad range of applicationsColloidal synthesis has emerged as an inexpensive, scalable and highly-tunable alternative to exfoliated andCVD-grown TMDsIf colloidal methods have to become a true alternative, they should be benchmarked relative to CVD-grown andexfoliated TMDsTransient Absorption – Band Gap RenormalizationTransient Absorption – Exciton Dynamicspump-probe spectroscopymeasure transient absorbance ΔA2H MoS2  (XRD and UV-vis)few-layered (AFM)multiple bands of ∆𝐴 < 0and ∆𝐴 > 0 around excitonsfirst order kinetics spectrum reflects a spectral shiftThe synthesis yields few-layered colloidal 2H MoS2 nanosheetsA spectral shift of the transition energies governs the ΔA spectrum at long pump-probe delays𝐴 𝐸, 𝑡 = 𝑎𝐴𝑒−𝐸−𝐸𝐴 ²𝑤𝐴² + 𝑎𝐵𝑒−𝐸−𝐸𝐵 ²𝑤𝐵² + 𝐵short-living bleachesaround band-gapdeconvultion of excited state spectrum A = A0 + ΔA according toTransient Absorption – Intraband Absorptionphotoinduced absorptionrelated to intraband transitionssimilar dynamics above gap and sub-gapConclusion – Model for Charge-Carrier Decaynetto bleaches due to state fillingrapid decay of A exciton bleachdynamics of the spectral shift and broadeninghappen on a remarkably similar time scaletrapping of holesdecay net A bleachdecay sub-gap photoinduced abs. first-order decayslower non-rad. capture eventsrelaxation of band-gap renorm.A time-dependent spectral deconvolution of ΔA highlights simultaneous rapidchanges on the state filling, spectral shifting and broadening dynamicsA comparison between the colloidal materials as measured here and the existingliterature on CVD-grown TMDs points toward very similar photogenerated carrierdynamics, eventhough an entirely different chemistry is involved in the TMD production

Ultrafast carrier dynamics in few-layer colloidal molybdenum disulfide probed by broadband transient absorption spectroscopy

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Ultrafast carrier dynamics in few-layer colloidal molybdenum disulfide probed by broadband transient absorption spectroscopy

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