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Efficient Auger electron cooling in seemingly unfavourable configurations: hole traps and electrochemical charging

Califano, M. (2008) Efficient Auger electron cooling in seemingly unfavourable configurations: hole traps and electrochemical charging. The Journal of Physical Chemistry C, 112 (23). pp. 8570-8574.


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The absence of a phonon bottleneck in the intraband relaxation between p-like and s-like electron states in CdSe nanocrystals is generally ascribed to efficient inelastic scattering with the photogen- erated hole (Auger cooling). However the fast relaxation of electrons observed in the absence of a hole or in the presence of a hole trapped in a surface state have raised serious questions about the suitability of this model. The semiempirical pseudopotential calculations reported here show that electron-electron scattering in chemically reduced or electrochemically charged (i.e., hole-less) CdSe nanocrystals leads to short p electron lifetimes comparable to those calculated in the presence of a photogenerated hole delocalised in the dot core. Furthermore, it is shown that efficient energy transfer can also be achieved between a delocalised electron and a surface-trapped hole leading to short p electron lifetimes in the (sub-) ps range. These results are in quantitative agreement with experiment and consistent with the Auger interpretation of the electron relaxation. The fast sub-ps electron relaxation times calculated in the presence of a hole localised in a shallow surface trap raise the intriguing question of whether in earlier measurements in TOPO-capped nanocrystals the hole was indeed delocalised within the dot core, as it was believed at the time, or whether it could have been in a trap state.

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: Sherpa Assistant
Date Deposited: 15 Aug 2008 13:09
Last Modified: 26 Mar 2015 14:11
Published Version: http://dx.doi.org/10.1021/jp7104743
Status: Published
Publisher: American Chemical Society
Identification Number: 10.1021/jp7104743
URI: http://eprints.whiterose.ac.uk/id/eprint/4330

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