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

Journal Article · Mon Sep 25 00:00:00 EDT 2017 · ACS Photonics

DOI:https://doi.org/10.1021/acsphotonics.7b00560· OSTI ID:1413789

Fuhr, Addis S. ^[1]; Yun, Hyeong Jin ^[2]; Makarov, Nikolay S. ^[2]; Li, Hongbo ^[2]; McDaniel, Hunter ^[3]; Klimov, Victor I.

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1. Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States, Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States
2. Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
3. UbiQD, LLC, 134 East Gate Drive, Los Alamos, New Mexico 87544, United States

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 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).

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Advanced Solar Photophysics (CASP)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1413789
• Alternate ID(s): OSTI ID: 1438124
• Report Number(s): LA-UR-18-21643
• Journal Information: ACS Photonics, Journal Name: ACS Photonics Vol. 4 Journal Issue: 10; ISSN 2330-4022
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Analytical Chemistry