Source: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-2-A350
Timestamp: 2019-04-21 08:52:52+00:00

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CdSe/CdS/ZnS core-shell-shell quantum dots (QDs) were synthesized by using a solution process. High-resolution transmission electron microscopy images and energy dispersive spectroscopy profiles confirmed that stoichiometric CdSe/CdS/ZnS core-shell-shell QDs were formed. Ultraviolet-visible absorption and photoluminescence (PL) spectra of CdSe/CdS/ZnS core-shell-shell QDs showed the dominant excitonic transitions from the ground electronic subband to the ground hole subband (1S(e)-1S3/2(h)). The PL mechanism is suggested; the carriers generated by the exciting high-energy photons in the shell region are relaxed to the band-edge states of the core region and recombined to emit lower-energy photons. The activation energy of the carriers confined in the CdSe/CdS/ZnS core-shell-shell QDs, as obtained from temperature-dependent PL spectra, was 200 meV. The quantum efficiency of the CdSe/CdS/ZnS core-shell-shell QDs at 300 K was estimated to be approximately 57%.
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Fig. 1 Schematic illustration of fabrication steps for the CdSe/CdS/ZnS core-shell-shell quantum dots.
Fig. 2 (a) Schematic diagram of the CdSe/CdS/ZnS core-shell-shell quantum dots. (b) Transmission electron microscopy image, and (c) energy dispersive spectroscopy profile of the CdSe/CdS/ZnS core-shell-shell quantum dots.
Fig. 3 Normalized UV-visible absorption (solid line) and photoluminescence (dashed line) spectra of the CdSe/CdS/ZnS core-shell-shell quantum dots.
Fig. 4 Images of (a) before and (b) after exposures of UV excitation wavelength of 365 nm for CdSe/CdS/ZnS core-shell-shell quantum dots. (c) Schematic diagram of the optical processes in the CdSe/CdS/ZnS core-shell-shell quantum dots.
Fig. 5 Photoluminescence spectra measured at several temperatures for CdSe/CdS/ZnS core-shell-shell quantum dots.
Fig. 6 (a) Integrated photoluminescence intensity as functions of the reciprocal temperature for CdSe/CdS/ZnS core-shell-shell quantum dots. Solid rectangles represent experimental data and the solid line indicates the fitting curve. (b) Quantum efficiency as functions of the temperature for CdSe/CdS/ZnS core-shell-shell quantum dots.

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