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Identity of the reversible hole traps in InP/ZnSe core/shell quantum dots

Journal Article · · Journal of Chemical Physics
DOI:https://doi.org/10.1063/5.0123956· OSTI ID:1891491
 [1];  [2];  [2];  [3];  [3];  [3];  [3];  [2]
  1. Univ. of California, Merced, CA (United States); Nanosys, Inc.
  2. Univ. of California, Merced, CA (United States)
  3. Nanosys, Inc., Milpitas, CA (United States)
+ Show Author Affiliations
Density functional theory calculations are combined with time-resolved photoluminescence experiments to identify the species responsible for reversible trapping of holes following photoexcitation of InP/ZnSe/ZnS core/shell/shell quantum dots (QDs) having excess indium in the shell. Several possible assignments are considered, and a substitutional indium adjacent to a zinc vacancy, In3+/VZn2-, is found to be the most likely. This assignment is consistent with the observation that trapping occurs only when the QD has excess indium and is supported by experiments showing that the addition of zinc oleate or acetate decreases the extent of trapping, presumably by filling some of the vacancy traps. We also show that addition of alkyl carboxylic acids causes increased trapping, presumably by creation of additional zinc vacancies. The calculations show that either a single In2+ ion or an In2+-In3+ dimer is much too easily oxidized to form the reversible traps observed experimentally, while In3+ is far too difficult to oxidize. Additional experimental data on InP/ZnSe/ZnS QDs synthesized in the absence of chloride demonstrates that the reversible traps are not associated with Cl-. Furthermore, a zinc vacancy adjacent to a substitutional indium is calculated to have its highest occupied orbitals about 1 eV above the top of the valence band of bulk ZnSe, in the appropriate energy range to act as reversible traps for quantum confined holes in the InP valence band. The associated orbitals are predominantly composed of p orbitals on the Se atoms adjacent to the Zn vacancy.
Research Organization:
Nanosys, Inc., Milpitas, CA (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
EE0009164
OSTI ID:
1891491
Alternate ID(s):
OSTI ID: 1896338
Journal Information:
Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 17 Vol. 157; ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
density functional theory
hole traps
indium phosphide
photophysics
quantum dots