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 journalArticlepeer-review

132 Citations (Scopus)


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
Issue number11
Publication statusPublished - Nov 9 2011

ASJC Scopus subject areas

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

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