Exciton-Phonon Coupling and Carrier Relaxation in PbS Quantum Dots: The Case of Carboxylate Ligands

Some ligand-nanocrystal combinations exhibit rapid cooling of highly excited electronic states while other nanocrystal/shell combinations do not appear to have this effect. There remains a need to identify the distinguishing properties of ligand-nanocrystal interactions that avoid such rapid relaxation processes to guide the design of colloidal quantum dots (QDs) that take advantage of multiple exciton generation or hot-carrier extraction processes. Here, we use mid-infrared transient absorption spectroscopy to investigate the influence that carboxylate ligands with distinct excited state surface chemistries has on exciton-phonon coupling and hot exciton relaxation in PbS quantum dot (QD) films. Our findings reveal that despite significant differences in the excited state surface chemistry of oleate (OA) and iodide/mercaptopropionic acid (I-/MPA) ligands, PbS QD films passivated with both ligand types exhibit identical electronic relaxation rates and exciton-phonon coupling strengths within experimental precision. The data suggest that the inorganic lattice is the principal source of exciton-phonon coupling that influences hot exciton relaxation, rather than the vibronic modes of carboxylate ligands. The size-dependent nature of the exciton-phonon coupling strength is consistent with the localization of charge on the QD surfaces, which enhances the mixing of electronic and nuclear coordinates particularly when the electronic states are more quantum confined in smaller nanocrystals.



Work Title Exciton-Phonon Coupling and Carrier Relaxation in PbS Quantum Dots: The Case of Carboxylate Ligands
Open Access
  1. Eric R. Kennehan
  2. Kyle T. Munson
  3. Christopher Grieco
  4. Grayson S. Doucette
  5. Ashley R. Marshall
  6. Matthew C. Beard
  7. John B. Asbury
  1. Excited states
  2. Ligands
  3. Light absorption
  4. Nanocrystals
  5. Quantum dots
License In Copyright (Rights Reserved)
Work Type Article
  1. Journal of Physical Chemistry C
Publication Date October 8, 2021
Publisher Identifier (DOI)
  1. https://doi.org/10.1021/acs.jpcc.1c05803
Deposited January 30, 2023




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Work History

Version 1

  • Created
  • Added PbS_Carboxylate_Ligands_Carrier_Cooling_ReReSubmitted.pdf
  • Added Creator Eric R. Kennehan
  • Added Creator Kyle T. Munson
  • Added Creator Christopher Grieco
  • Added Creator Grayson S. Doucette
  • Added Creator Ashley R. Marshall
  • Added Creator Matthew C. Beard
  • Added Creator John B. Asbury
  • Published
  • Updated Keyword, Publication Date Show Changes
    • Excited states, Ligands, Light absorption, Nanocrystals, Quantum dots
    Publication Date
    • 2021-10-21
    • 2021-10-08
  • Updated