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Electron relaxation following UV excitation in CdSe nanocrystals: sub-picosecond-fast population of the 1PStates across a gap wider than 10 phonon energies

Califano, M. (2009) Electron relaxation following UV excitation in CdSe nanocrystals: sub-picosecond-fast population of the 1PStates across a gap wider than 10 phonon energies. The Journal of Physical Chemistry C, 113 (46). pp. 19859-19862. ISSN 1932-7447

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Abstract

The typical energy separation between D-like and P-like electronic states in CdSe nanocrystals is often of similar magnitude to the S-P splitting in the conduction band and would therefore similarly preclude efficient electron decay via multiple phonon emission. Despite the puzzling observation of fast D-to-P intraband relaxation, however, little is known about the mechanisms governing it. This work shows that the same process responsible for fast P-to-S electron decay, namely Auger cooling, plays a fundamental role to allow fast population of the P state, from higher excited states, in case of high-energy excitations. Since in nanocrystals the latter are employed to initiate carrier multiplication, where multiple excitons are created from the absorption of a single photon, the D electron lifetimes calculated here could provide a reference for the estimate of the carrier multipli- cation time constant, the magnitude of which is still object of intense debate. These results also provide a further proof of the suitability of the Auger cooling model to explain electron relaxation in semiconductor nanocrystals.

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 16:08
Last Modified: 29 Sep 2010 14:25
Published Version: http://dx.doi.org/10.1021/jp907755j
Status: Published
Publisher: American Chemical Society
Refereed: Yes
Identification Number: 10.1021/jp907755j
URI: http://eprints.whiterose.ac.uk/id/eprint/10245

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