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Proceedings Paper

Temperature dependence of hot carrier relaxation in PbSe nanocrystals: an ab initio study
Author(s): Hua Bao; Bradley F. Habenicht; Oleg V. Prezhdo; Xiulin Ruan; Xianfan Xu
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Paper Abstract

Temperature dependent dynamics of phonon-assisted relaxation of hot carriers, both electrons and holes, is studied in a PbSe nanocrystal using ab initio time-domain density functional theory. The electronic structure is first calculated, showing that the hole states are denser than the electron states. Fourier transforms of the time resolved energy levels show that the hot carriers couple to both acoustic and optical phonons. At higher temperature, more phonon modes in the high frequency range participate in the relaxation process due to their increased occupation number. The phonon-assisted hot carrier relaxation time is predicted using non-adiabatic molecular dynamics, and the results clearly show a temperature-activation behavior. The complex temperature dependence is attributed to the combined effects of the phonon occupation number and the thermal expansion. Comparing the simulation results with experiments, we suggest that the multiphonon relaxation channel is efficient at high temperature, while the Auger-like process may dominate the relaxation at low temperature. This combined mechanism can explain the weak temperature dependence at low temperature and stronger temperature dependence at higher temperature.

Paper Details

Date Published: 20 August 2009
PDF: 11 pages
Proc. SPIE 7411, Nanoscale Photonic and Cell Technologies for Photovoltaics II, 741106 (20 August 2009); doi: 10.1117/12.826766
Show Author Affiliations
Hua Bao, Purdue Univ. (United States)
Bradley F. Habenicht, Univ. of Washington (United States)
Oleg V. Prezhdo, Univ. of Washington (United States)
Xiulin Ruan, Purdue Univ. (United States)
Xianfan Xu, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 7411:
Nanoscale Photonic and Cell Technologies for Photovoltaics II
Loucas Tsakalakos, Editor(s)

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