High-efficiency carrier multiplication through direct photogeneration of multi-excitons via virtual single-exciton states

Richard D. Schaller, Vladimir M. Agranovich, Victor I. Klimov

Research output: Contribution to journalArticle

413 Citations (Scopus)

Abstract

We have previously demonstrated that absorption of a single photon by a nanocrystal quantum dot can generate multiple excitons with an efficiency of up to 100%. This effect, known as carrier multiplication, should lead to substantial improvements in the performance of a variety of optoelectronic and photocatalytic devices, including solar cells, low-threshold lasers and entangled photon sources. Here we present detailed analysis of the dynamics that govern the ultrafast growth of multi-exciton populations in CdSe and PbSe nanocrystals and propose a model of how such populations arise. Our analysis indicates that the generation of multi-excitons in these systems takes less than 200 fs, which suggests that it is an instantaneous event. We explain this in terms of their direct photogeneration via multiple virtual single-exciton states. This process relies on both the confinement-enhanced Coulomb coupling between single excitons and multi-excitons and the large spectral density of high-energy single- and multi-exciton resonances that occur in semiconductor nanocrystals.

Original languageEnglish
Pages (from-to)189-194
Number of pages6
JournalNature Physics
Volume1
Issue number3
DOIs
Publication statusPublished - Dec 1 2005

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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