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Direct and inverse Auger processes in InAs nanocrystals: can the decay signature of a trion be mistaken for carrier multiplication?

Califano, M. (2009) Direct and inverse Auger processes in InAs nanocrystals: can the decay signature of a trion be mistaken for carrier multiplication? ACS Nano, 3 (9). pp. 2706-2714. ISSN 1936-0851


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A complete and detailed theoretical investigation of the main processes involved in the controversial detection and quantification of carrier multiplication (CM) is presented, providing a coherent and comprehensive picture of excited state relaxation in InAs nanocrystals (NCs). The observed rise and decay times of the 1S transient bleach are reproduced, in the framework of the Auger model, using an atomistic semiempirical pseudopotential method, achieving excellent agreement with experiment. The CM time constants for small core-only and core/shell nanocrystals are obtained as a function of the excitation energy, assuming an impact-ionization-like process. The resulting lifetimes at energies close to the observed CM onset are consistent with the upper limits deduced experimentally from PbSe and CdSe samples. Most interestingly, as the Auger recombination lifetimes calculated for charged excitons are found to be of a similar order of magnitude to those computed for biexcitons, both species are expected to exhibit the fast decay component in NC population dynamics so far attributed exclusively to the presence of biexcitons and therefore identified as the signature of CM occurrence in high-energy low-pump-fluence spectroscopic studies. However, the ratio between trions and biexcitons time constants is found to be larger than the typical experimental accuracy. It is therefore concluded that, in InAs NCs, it should be experimentally possible to discriminate between the two species and that the origin of the observed discrepancies in CM yields is unlikely to lay in the presence of charged excitons.

Item Type: Article
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Engineering (Leeds) > School of Electronic & Electrical Engineering (Leeds) > Institute of Microwaves and Photonics (Leeds)
Depositing User: Repository Officer
Date Deposited: 09 Dec 2009 16:03
Last Modified: 26 Mar 2015 10:46
Published Version: http://dx.doi.org/10.1021/nn900461f
Status: Published
Publisher: American Chemical Society
Refereed: Yes
Identification Number: 10.1021/nn900461f
URI: http://eprints.whiterose.ac.uk/id/eprint/10244

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