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Title: Defect states and charge transport in quantum dot solids

Defects at the surface of semiconductor quantum dots (QDs) give rise to electronic states within the gap, which are detrimental to charge transport properties of QD devices. We investigated charge transport in silicon quantum dots with deep and shallow defect levels, using ab initio calculations and constrained density functional theory. We found that shallow defects may be more detrimental to charge transport than deep ones, with associated transfer rates differing by up to 5 orders of magnitude for the small dots (1-2 nm) considered here. Hence, our results indicate that the common assumption, that the ability of defects to trap charges is determined by their position in the energy gap of the QD, is too simplistic, and our findings call for a reassessment of the role played by shallow defects in QD devices. Altogether, our results highlight the key importance of taking into account the atomistic structural properties of QD surfaces when investigating transport properties.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [2] ;  [3]
  1. Univ. of Chicago, Chicago, IL (United States)
  2. Argonne National Lab. (ANL), Lemont, IL (United States)
  3. Univ. of Chicago, Chicago, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 29; Journal Issue: 3; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC); Energy Frontier Research Center; Center for Advanced Solar Photophysics; National Institute of Standards and Technology (NIST), Center for Hierarchical Materials Design (CHiMaD)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; Charge Transfer; Constrained DFT; Defect; Nanocrystal; Nanostructure; Quantum dot; Transport
OSTI Identifier:
1352511

Brawand, Nicholas P., Goldey, Matthew B., Vörös, Márton, and Galli, Giulia. Defect states and charge transport in quantum dot solids. United States: N. p., Web. doi:10.1021/acs.chemmater.6b04631.
Brawand, Nicholas P., Goldey, Matthew B., Vörös, Márton, & Galli, Giulia. Defect states and charge transport in quantum dot solids. United States. doi:10.1021/acs.chemmater.6b04631.
Brawand, Nicholas P., Goldey, Matthew B., Vörös, Márton, and Galli, Giulia. 2017. "Defect states and charge transport in quantum dot solids". United States. doi:10.1021/acs.chemmater.6b04631. https://www.osti.gov/servlets/purl/1352511.
@article{osti_1352511,
title = {Defect states and charge transport in quantum dot solids},
author = {Brawand, Nicholas P. and Goldey, Matthew B. and Vörös, Márton and Galli, Giulia},
abstractNote = {Defects at the surface of semiconductor quantum dots (QDs) give rise to electronic states within the gap, which are detrimental to charge transport properties of QD devices. We investigated charge transport in silicon quantum dots with deep and shallow defect levels, using ab initio calculations and constrained density functional theory. We found that shallow defects may be more detrimental to charge transport than deep ones, with associated transfer rates differing by up to 5 orders of magnitude for the small dots (1-2 nm) considered here. Hence, our results indicate that the common assumption, that the ability of defects to trap charges is determined by their position in the energy gap of the QD, is too simplistic, and our findings call for a reassessment of the role played by shallow defects in QD devices. Altogether, our results highlight the key importance of taking into account the atomistic structural properties of QD surfaces when investigating transport properties.},
doi = {10.1021/acs.chemmater.6b04631},
journal = {Chemistry of Materials},
number = 3,
volume = 29,
place = {United States},
year = {2017},
month = {1}
}