Light amplification in the single-exciton regime using exciton-exciton repulsion in type-II nanocrystal quantum dots

Jagjit Nanda, Sergei A. Ivanov, Marc Achermann, Ilya Bezel, Andrei Piryatinski, Victor I Klimov

Research output: Contribution to journalArticle

62 Citations (Scopus)

Abstract

Optical gain in ultrasmall semiconductor nanocrystals requires that some of the nanoparticles in the ensemble be excited with multiple electron-hole pairs (multiexcitons). A significant complication arising from this multiexciton nature of optical amplification is the ultrafast gain decay induced by nonradiative Auger recombination. Here, we develop a simple model for analyzing optical gain in the nanocrystals in the presence of exciton-exciton (X-X) interactions. This analysis indicates that if the X-X interaction is repulsive and its energy is large compared to the ensemble line width of the emitting transition, optical gain can occur in the single-exciton regime without involvement of multiexcitons. We further analyze theoretically and experimentally X-X interactions in type-II heteronanocrystals of CdS (core)/ZnSe (shell) and ZnTe (core)/CdSe (shell) and show that they can produce giant repulsion energies of more than 100 meV resulting from a significant local charge density generated as a result of spatial separation between electrons and holes. We observe that the dynamical and spectral properties of optical gain in type-II nanocrystals are distinctly different from those of multiexciton gain in traditional type-I nanocrystals and are consistent with those expected for the single-exciton regime. An important implication of these results is the possibility of a significant increase in the optical-gain lifetime, which could simplify applications of chemically synthesized nanocrystals in practical lasing technologies and perhaps allow for lasing using electrical injection.

Original languageEnglish
Pages (from-to)15382-15390
Number of pages9
JournalJournal of Physical Chemistry C
Volume111
Issue number42
DOIs
Publication statusPublished - Oct 25 2007

Fingerprint

Optical gain
Excitons
Nanocrystals
Semiconductor quantum dots
Amplification
nanocrystals
quantum dots
excitons
Electrons
lasing
Charge density
Linewidth
LDS 751
Semiconductor materials
Nanoparticles
interactions
optical transition
injection
life (durability)
nanoparticles

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Light amplification in the single-exciton regime using exciton-exciton repulsion in type-II nanocrystal quantum dots. / Nanda, Jagjit; Ivanov, Sergei A.; Achermann, Marc; Bezel, Ilya; Piryatinski, Andrei; Klimov, Victor I.

In: Journal of Physical Chemistry C, Vol. 111, No. 42, 25.10.2007, p. 15382-15390.

Research output: Contribution to journalArticle

Nanda, Jagjit ; Ivanov, Sergei A. ; Achermann, Marc ; Bezel, Ilya ; Piryatinski, Andrei ; Klimov, Victor I. / Light amplification in the single-exciton regime using exciton-exciton repulsion in type-II nanocrystal quantum dots. In: Journal of Physical Chemistry C. 2007 ; Vol. 111, No. 42. pp. 15382-15390.
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