Article abstract
Nature Physics 1, 189 - 194 (2005)
doi:10.1038/nphys151
Subject Categories: Electronics, photonics and device physics | Condensed-matter physics | Nanotechnology
High-efficiency carrier multiplication through direct photogeneration of multi-excitons via virtual single-exciton states
Richard D. Schaller1, Vladimir M. Agranovich2,3 and Victor I. Klimov1
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.
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow obl. 142190, Russia
- UTD-NanoTech Institute, The University of Texas at Dallas, Richardson, Texas 75083, USA
Correspondence to: Victor I. Klimov1 e-mail: klimov@lanl.gov
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