TIPS-pentacene triplet exciton generation on PbS quantum dots results from indirect sensitization

Christopher M. Papa, Sofia Garakyaraghi, Devin B. Granger, John E. Anthony, Felix N. Castellano

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Many fundamental questions remain in the elucidation of energy migration mechanisms across the interface between semiconductor nanomaterials and molecular chromophores. The present transient absorption study focuses on PbS quantum dots (QDs) of variable size and band-edge exciton energy (ranging from 1.15 to 1.54 eV) post-synthetically modified with a carboxylic acid-functionalized TIPS-pentacene derivative (TPn) serving as the molecular triplet acceptor. In all instances, selective excitation of the PbS NCs at 743 nm leads to QD size-dependent formation of an intermediate with time constants ranging from 2-13 ps, uncorrelated to the PbS QD valence band potential. However, the rate constant for the delayed formation of the TPn triplet excited state markedly increases with increasing PbS conduction band energy, featuring a parabolic Marcus free energy dependence in the normal region. These observations provide evidence of an indirect triplet sensitization process being inconsistent with a concerted Dexter-like energy transfer process. The collective data are consistent with the generation of an intermediate resulting from hole trapping of the initial PbS excited state by midgap states, followed by formation of the TPn triplet excited state whose rate constant and yield increases with decreasing quantum dot size.

Original languageEnglish
Pages (from-to)5690-5696
Number of pages7
JournalChemical Science
Volume11
Issue number22
DOIs
StatePublished - Jun 14 2020

Bibliographical note

Funding Information:
We acknowledge support for this work from the Organic Materials Chemistry program in the Air Force Office of Scientic Research (FA9550-18-1-0331). Electron microscopy was performed at the Analytical Instrumentation Facility (AIF) at North Carolina State University, which is supported by the State of North Carolina and the National Science Foundation (Award Number ECCS-1542015). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI).

Publisher Copyright:
© The Royal Society of Chemistry 2020.

ASJC Scopus subject areas

  • Chemistry (all)

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