Measuring electron and hole transfer in core/shell nanoheterostructures

Chi Hung Chuang, Tennyson L. Doane, Shun S. Lo, Gregory D. Scholes, Clemens Burda

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

Using femtosecond transient absorption and time-resolved photoluminescence spectroscopy, we studied the electron versus hole dynamics in photoexcited quasi-type-II heterostructured nanocrystals with fixed CdTe core radii and varying CdSe shell coverage. By choosing the pump wavelength in resonance with the core or the shell states, respectively, we were able to measure the excited electron and hole dynamics selectively. Both, the core- and the shell-excited CdTe/CdSe nanocrystals showed the same spectral emission and photoluminescence lifetimes, indicating that ultrafast electron and hole transfer across the core/shell interface resulted in the identical long-lived charge transfer state. Both charge carriers have subpicosecond transfer rates through the interface, but the subsequent relaxation rates of the hole (τdec ∼ 800 ps) and electron (τavg ∼ 8 ps) are extremely different. On the basis of the presented transient absorption measurements and fitting of the steady-state spectra, we find that the electron transfer occurs in the Marcus inverted region and mixing between the CdTe exciton and charge transfer states takes place and therefore needs to be considered in the analysis.

Original languageEnglish (US)
Pages (from-to)6016-6024
Number of pages9
JournalACS Nano
Volume5
Issue number7
DOIs
StatePublished - Jul 26 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Keywords

  • Marcus theory
  • charge transfer
  • core/shell quantum dots
  • electron/hole relaxation
  • femtosecond transient absorption
  • type-II heterostructure

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