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 language | English |
|---|---|
| Pages (from-to) | 15382-15390 |
| Number of pages | 9 |
| Journal | Journal of Physical Chemistry C |
| Volume | 111 |
| Issue number | 42 |
| DOIs | |
| Publication status | Published - Oct 25 2007 |
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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 journal › Article
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TY - JOUR
T1 - Light amplification in the single-exciton regime using exciton-exciton repulsion in type-II nanocrystal quantum dots
AU - Nanda, Jagjit
AU - Ivanov, Sergei A.
AU - Achermann, Marc
AU - Bezel, Ilya
AU - Piryatinski, Andrei
AU - Klimov, Victor I
PY - 2007/10/25
Y1 - 2007/10/25
N2 - 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.
AB - 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.
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U2 - 10.1021/jp0738659
DO - 10.1021/jp0738659
M3 - Article
VL - 111
SP - 15382
EP - 15390
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 42
ER -