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Title: The use of bulk states to accelerate the band edge state calculation of a semiconductor quantum dot

Abstract

We present a new technique to accelerate the convergence of the folded spectrum method in empirical pseudopotential band edge state calculations for colloidal quantum dots. We use bulk band states of the materials constituent of the quantum dot to construct initial vectors and a preconditioner. We apply these to accelerate the convergence of the folded spectrum method for the interior states at the top of the valence and the bottom of the conduction band. For large CdSe quantum dots, the number of iteration steps until convergence decreases by about a factor of 4 compared to previous calculations.

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States). E-mail: voemel@eecs.berkeley.edu
  2. Computer Science Department, University of Tennessee, Knoxville, TN 37996-3450 (United States). E-mail: tomov@cs.utk.edu
  3. Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States). E-mail: LWWang@lbl.gov
  4. Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States). E-mail: OAMarques@lbl.gov
  5. Computer Science Department, University of Tennessee, Knoxville, TN 37996-3450 (United States). E-mail: dongarra@cs.utk.edu
Publication Date:
OSTI Identifier:
20991577
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Computational Physics; Journal Volume: 223; Journal Issue: 2; Other Information: DOI: 10.1016/j.jcp.2006.10.005; PII: S0021-9991(06)00473-6; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CADMIUM SELENIDES; CONVERGENCE; ELECTRONIC STRUCTURE; QUANTUM DOTS; SEMICONDUCTOR MATERIALS; SPECTRA; VECTORS

Citation Formats

Voemel, Christof, Tomov, Stanimire Z., Wang, Lin-Wang, Marques, Osni A., and Dongarra, Jack J. The use of bulk states to accelerate the band edge state calculation of a semiconductor quantum dot. United States: N. p., 2007. Web. doi:10.1016/j.jcp.2006.10.005.
Voemel, Christof, Tomov, Stanimire Z., Wang, Lin-Wang, Marques, Osni A., & Dongarra, Jack J. The use of bulk states to accelerate the band edge state calculation of a semiconductor quantum dot. United States. doi:10.1016/j.jcp.2006.10.005.
Voemel, Christof, Tomov, Stanimire Z., Wang, Lin-Wang, Marques, Osni A., and Dongarra, Jack J. Tue . "The use of bulk states to accelerate the band edge state calculation of a semiconductor quantum dot". United States. doi:10.1016/j.jcp.2006.10.005.
@article{osti_20991577,
title = {The use of bulk states to accelerate the band edge state calculation of a semiconductor quantum dot},
author = {Voemel, Christof and Tomov, Stanimire Z. and Wang, Lin-Wang and Marques, Osni A. and Dongarra, Jack J.},
abstractNote = {We present a new technique to accelerate the convergence of the folded spectrum method in empirical pseudopotential band edge state calculations for colloidal quantum dots. We use bulk band states of the materials constituent of the quantum dot to construct initial vectors and a preconditioner. We apply these to accelerate the convergence of the folded spectrum method for the interior states at the top of the valence and the bottom of the conduction band. For large CdSe quantum dots, the number of iteration steps until convergence decreases by about a factor of 4 compared to previous calculations.},
doi = {10.1016/j.jcp.2006.10.005},
journal = {Journal of Computational Physics},
number = 2,
volume = 223,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}
  • We present a new technique to accelerate the convergence of the folded spectrum method in empirical pseudopotential band edge state calculations for colloidal quantum dots. We use bulk band states of the materials constituent of the quantum dot to construct initial vectors and a preconditioner. We apply these to accelerate the convergence of the folded spectrum method for the interior states at the top of the valence and the bottom of the conduction band. For large CdSe quantum dots, the number of iteration steps until convergence decreases by about a factor of 4 compared to previous calculations.
  • We introduce a tight-binding approach to model the emission dynamics of a quantum-dot in realistic, photonic-crystal-slab coupled-cavity systems. We apply our approach to a quantum-dot strongly coupled at the band edge of a lossy coupled-cavity waveguide and calculate the quantum-dot dynamics as well as the photon dynamics along the waveguide. We show that the condition for strong coupling is simply parametrized in terms of the waveguide loss and find that the key signature of the strong-coupling, Rabi oscillations, could be observed via time-resolved photon detection.
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  • Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the bandmore » edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. We expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.« less
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