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

Eric Kennehan, Kyle Munson, Christopher Grieco, Grayson Doucette, Ashley Marshall, Matthew Beard, John Asbury

Research output: Contribution to journalArticlepeer-review

5 Scopus Citations


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.

Original languageAmerican English
Pages (from-to)22622-22629
Number of pages8
JournalJournal of Materials Chemistry C
Issue number41
StatePublished - 21 Oct 2021

Bibliographical note

Publisher Copyright:
© Authors 2021

NREL Publication Number

  • NREL/JA-5900-80431


  • carrier dynamics
  • ligand chemistry
  • QDs
  • solar-photochemistry


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