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Title: Light Emission Mechanisms in CuInS 2 Quantum Dots Evaluated by Spectral Electrochemistry

Luminescent CuInS 2 (CIS) quantum dots (QDs) exhibit highly efficient intragap emission and long, hundreds-of-nanoseconds radiative lifetimes. These spectral properties, distinct from structurally similar II–VI QDs, can be explained by the involvement of intragap defect states containing a localized hole capable of coupling with a conduction band electron for a radiative transition. However, the absolute energies of the intragap and band-edge states, the structure of the emissive defect(s), and the role and origin of nonemissive decay channels still remain poorly understood. Here, we address these questions by applying methods of spectral electrochemistry. Cyclic voltammetry measurements reveal a well-defined intragap state whose redox potential is close to that of the Cu x defect state (where x = 1+ or 2+). The energy offset of this state from the valence band accounts well for the apparent photoluminescence Stokes shift observed in optical spectra. These results provide direct evidence that Cu-related defects serve as emission centers responsible for strong intragap emission from CIS QDs. We then use in situ spectroelectrochemistry to reveal two distinct emission pathways based on the differing oxidation states of Cu defects, which can be controlled by altering QD stoichiometry (1+ for stoichiometric QDs and 2+ for Cu-deficient QDs).
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ; ORCiD logo [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of California, Los Angeles, CA (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. UbiQD, LLC, Los Alamos, NM(United States)
Publication Date:
Report Number(s):
LA-UR-18-21643
Journal ID: ISSN 2330-4022
Grant/Contract Number:
AC52-06NA25396
Type:
Published Article
Journal Name:
ACS Photonics
Additional Journal Information:
Journal Volume: 4; Journal Issue: 10; Journal ID: ISSN 2330-4022
Publisher:
American Chemical Society (ACS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Advanced Solar Photophysics (CASP)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Analytical Chemistry
OSTI Identifier:
1413789
Alternate Identifier(s):
OSTI ID: 1438124

Fuhr, Addis S., Yun, Hyeong Jin, Makarov, Nikolay S., Li, Hongbo, McDaniel, Hunter, and Klimov, Victor I.. Light Emission Mechanisms in CuInS2 Quantum Dots Evaluated by Spectral Electrochemistry. United States: N. p., Web. doi:10.1021/acsphotonics.7b00560.
Fuhr, Addis S., Yun, Hyeong Jin, Makarov, Nikolay S., Li, Hongbo, McDaniel, Hunter, & Klimov, Victor I.. Light Emission Mechanisms in CuInS2 Quantum Dots Evaluated by Spectral Electrochemistry. United States. doi:10.1021/acsphotonics.7b00560.
Fuhr, Addis S., Yun, Hyeong Jin, Makarov, Nikolay S., Li, Hongbo, McDaniel, Hunter, and Klimov, Victor I.. 2017. "Light Emission Mechanisms in CuInS2 Quantum Dots Evaluated by Spectral Electrochemistry". United States. doi:10.1021/acsphotonics.7b00560.
@article{osti_1413789,
title = {Light Emission Mechanisms in CuInS2 Quantum Dots Evaluated by Spectral Electrochemistry},
author = {Fuhr, Addis S. and Yun, Hyeong Jin and Makarov, Nikolay S. and Li, Hongbo and McDaniel, Hunter and Klimov, Victor I.},
abstractNote = {Luminescent CuInS2 (CIS) quantum dots (QDs) exhibit highly efficient intragap emission and long, hundreds-of-nanoseconds radiative lifetimes. These spectral properties, distinct from structurally similar II–VI QDs, can be explained by the involvement of intragap defect states containing a localized hole capable of coupling with a conduction band electron for a radiative transition. However, the absolute energies of the intragap and band-edge states, the structure of the emissive defect(s), and the role and origin of nonemissive decay channels still remain poorly understood. Here, we address these questions by applying methods of spectral electrochemistry. Cyclic voltammetry measurements reveal a well-defined intragap state whose redox potential is close to that of the Cux defect state (where x = 1+ or 2+). The energy offset of this state from the valence band accounts well for the apparent photoluminescence Stokes shift observed in optical spectra. These results provide direct evidence that Cu-related defects serve as emission centers responsible for strong intragap emission from CIS QDs. We then use in situ spectroelectrochemistry to reveal two distinct emission pathways based on the differing oxidation states of Cu defects, which can be controlled by altering QD stoichiometry (1+ for stoichiometric QDs and 2+ for Cu-deficient QDs).},
doi = {10.1021/acsphotonics.7b00560},
journal = {ACS Photonics},
number = 10,
volume = 4,
place = {United States},
year = {2017},
month = {9}
}