Ultrafast electron trapping at the surface of semiconductor nanocrystals: Excitonic and biexcitonic processes

Jonathan I. Saari, Eva A. Dias, Danielle Reifsnyder, Michael M. Krause, Brenna R. Walsh, Christopher B. Murray, Patanjali Kambhampati

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Aging of semiconductor nanocrystals (NCs) is well-known to attenuate the spontaneous photoluminescence from the band edge excitonic state by introduction of nonradiative trap states formed at the NC surface. In order to explore charge carrier dynamics dictated by the surface of the NC, femtosecond pump/probe spectroscopic experiments are performed on freshly synthesized and aged CdTe NCs. These experiments reveal fast electron trapping for aged CdTe NCs from the single excitonic state (X). Pump fluence dependence with excitonic state-resolved optical pumping enables directly populating the biexcitonic state (XX), which produces further accelerated electron trapping rates. This increase in electron trapping rate triggers coherent acoustic phonons by virtue of the ultrafast impulsive time scale of the surface trapping process. The observed trapping rates are discussed in terms of electron transfer theory.

Original languageEnglish (US)
Pages (from-to)4412-4421
Number of pages10
JournalJournal of Physical Chemistry B
Volume117
Issue number16
DOIs
StatePublished - Apr 25 2013

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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