Copper-doped inverted core/shell nanocrystals with "permanent" optically active holes

Ranjani Viswanatha, Sergio Brovelli, Anshu Pandey, Scott A. Crooker, Victor I. Klimov

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

We have developed a new class of colloidal nanocrystals composed of Cu-doped ZnSe cores overcoated with CdSe shells. Via spectroscopic and magneto-optical studies, we conclusively demonstrate that Cu impurities represent paramagnetic +2 species and serve as a source of permanent optically active holes. This implies that the Fermi level is located below the Cu 2+/Cu1+ state, that is, in the lower half of the forbidden gap, which is a signature of a p-doped material. It further suggests that the activation of optical emission due to the Cu level requires injection of only an electron without a need for a valence-band hole. This peculiar electron-only emission mechanism is confirmed by experiments in which the titration of the nanocrystals with hole-withdrawing molecules leads to enhancement of Cu-related photoluminescence while simultaneously suppressing the intrinsic, band-edge exciton emission. In addition to containing permanent optically active holes, these newly developed materials show unprecedented emission tunability from near-infrared (1.2 eV) to the blue (3.1 eV) and reduced losses from reabsorption due to a large Stokes shift (up to 0.7 eV). These properties make them very attractive for applications in light-emission and lasing technologies and especially for the realization of novel device concepts such as "zero-threshold" optical gain.

Original languageEnglish
Pages (from-to)4753-4758
Number of pages6
JournalNano Letters
Volume11
Issue number11
DOIs
Publication statusPublished - Nov 9 2011

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Nanocrystals
Copper
nanocrystals
Optical gain
copper
Electrons
Light emission
Valence bands
Fermi level
Titration
Excitons
light emission
Photoluminescence
Chemical activation
Impurities
Infrared radiation
Molecules
titration
lasing
electrons

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Mechanical Engineering

Cite this

Copper-doped inverted core/shell nanocrystals with "permanent" optically active holes. / Viswanatha, Ranjani; Brovelli, Sergio; Pandey, Anshu; Crooker, Scott A.; Klimov, Victor I.

In: Nano Letters, Vol. 11, No. 11, 09.11.2011, p. 4753-4758.

Research output: Contribution to journalArticle

Viswanatha, Ranjani ; Brovelli, Sergio ; Pandey, Anshu ; Crooker, Scott A. ; Klimov, Victor I. / Copper-doped inverted core/shell nanocrystals with "permanent" optically active holes. In: Nano Letters. 2011 ; Vol. 11, No. 11. pp. 4753-4758.
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