Ultrastrong Coupling Leads to Slowed Cooling of Hot Excitons in Few-Layer Transition-Metal Dichalcogenides

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Abstract

The excited-state dynamics of few-layer molybdenum disulfide (FL-MoS2) are studied in conditions of strong light-matter coupling to plasmon polaritons. Hot carrier extraction in these systems has been proposed due to the observation of slow cooling of the high-energy C exciton relative to the bandgap A exciton. Here, we show that in conditions of ultrastrong coupling to plasmon polaritons, the lifetimes of the two slowest C exciton decay processes are extended by factors of 1.5 and 5.8 in FL-MoS2. We hypothesize that strong coupling delocalization suppresses multiple decay mechanisms throughout the visible spectrum in MoS2such as defect scattering, intervalley scattering of band-nested excitations to the K-valley band edges, and exciton-exciton annihilation. We also find that decay from the upper to the lower hybrid mode is not ultrafast as seen in organic systems but in fact introduces an additional delay of ∼20 ps. Our observations show that strong coupling can be used to extend the lifetimes of hot excitons in FL-MoS2and potentially in other two-dimensional transition-metal dichalcogenides, with potential for above-bandgap photophysics and photochemistry applications such as hot carrier extraction, which could lead to more efficient solar energy conversion.

Original languageAmerican English
Pages (from-to)8710-8719
Number of pages10
JournalJournal of Physical Chemistry C
Volume126
Issue number20
DOIs
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

NREL Publication Number

  • NREL/JA-5900-82245

Keywords

  • carrier dynamics
  • exciton-polariton
  • MoS2
  • solar-photochemistry
  • strong coupling
  • surface plasmon polariton
  • transition-metal dichalcogenide
  • two-dimensional materials
  • ultrafast spectroscopy

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