TY - JOUR
T1 - Organometallic synthesis, structural and optical properties of CdSe quantum dots passivated with ternary AgZnS alloyed shell
AU - Adegoke, Oluwasesan
AU - Montaseri, Hanieh
AU - Nsibande, Sifiso A.
AU - Forbes, Patricia B.C.
N1 - Funding Information:
We gratefully acknowledge financial support from the Water Research Council ( WRC ) South Africa projects K5/2752 and K5/2438, and the University of Pretoria .
Publisher Copyright:
© 2021 Elsevier B.V.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/7
Y1 - 2021/7
N2 - We report on the surface passivation of a new alloyed ternary AgZnS shell layer on luminescent CdSe quantum dots (QDs) via the organometallic hot-injection pyrolysis of metal precursors, surfactant precursors and organic ligands in a non-coordinating solvent. Transmission electron microscopy, X-ray diffraction, Raman spectroscopy and UV/vis absorption and fluorescence emission spectrophotometry were used to characterize the QD nanocrystals. Fixed AgZnS shell alloying was used as the main fabrication strategy to engineer the band gap of CdSe/AgZnS core/alloyed shell QDs which in turn led to a blended mixture of homogenous and heterogenous particle size growth with spherical, quasi-spherical and trigonal-shaped particles. The crystal structure of CdSe/AgZnS QDs was mainly zinc blende but as the QDs size increased with time, a superimposition of zinc blende and wurtzite hexagonal structure was observed with the former being predominant in the diffraction pattern. The photoluminescence (PL) emission spectra of CdSe/AgZnS QDs were tuned across the visible region while the full width at half maximum was as low as 33 nm, representing an 8 nm decrease compared to 41 nm FWHM exhibited by CdSe QDs. As CdSe/AgZnS core/alloyed shell QDs grew with time, the PL quantum yield (QY) increased from 67% for CdSe to a maximum of ~100% for CdSe/AgZnS QDs and thereafter decreased steadily to a minimum of 36% upon further growth. By achieving ~100% PL QY, it appears that interfacial surface defect states in the core/alloyed shell QDs were completely eliminated via the AgZnS shell alloying process on the CdSe core. The unique optical properties exhibited by CdSe/AgZnS core/alloyed shell QDs as reported in this work shows great promise for light emitting QD applications.
AB - We report on the surface passivation of a new alloyed ternary AgZnS shell layer on luminescent CdSe quantum dots (QDs) via the organometallic hot-injection pyrolysis of metal precursors, surfactant precursors and organic ligands in a non-coordinating solvent. Transmission electron microscopy, X-ray diffraction, Raman spectroscopy and UV/vis absorption and fluorescence emission spectrophotometry were used to characterize the QD nanocrystals. Fixed AgZnS shell alloying was used as the main fabrication strategy to engineer the band gap of CdSe/AgZnS core/alloyed shell QDs which in turn led to a blended mixture of homogenous and heterogenous particle size growth with spherical, quasi-spherical and trigonal-shaped particles. The crystal structure of CdSe/AgZnS QDs was mainly zinc blende but as the QDs size increased with time, a superimposition of zinc blende and wurtzite hexagonal structure was observed with the former being predominant in the diffraction pattern. The photoluminescence (PL) emission spectra of CdSe/AgZnS QDs were tuned across the visible region while the full width at half maximum was as low as 33 nm, representing an 8 nm decrease compared to 41 nm FWHM exhibited by CdSe QDs. As CdSe/AgZnS core/alloyed shell QDs grew with time, the PL quantum yield (QY) increased from 67% for CdSe to a maximum of ~100% for CdSe/AgZnS QDs and thereafter decreased steadily to a minimum of 36% upon further growth. By achieving ~100% PL QY, it appears that interfacial surface defect states in the core/alloyed shell QDs were completely eliminated via the AgZnS shell alloying process on the CdSe core. The unique optical properties exhibited by CdSe/AgZnS core/alloyed shell QDs as reported in this work shows great promise for light emitting QD applications.
KW - CdSe
KW - Core/shell
KW - Photoluminescence
KW - Quantum dots
KW - Quantum yield
UR - http://www.scopus.com/inward/record.url?scp=85103332228&partnerID=8YFLogxK
U2 - 10.1016/j.jlumin.2021.118049
DO - 10.1016/j.jlumin.2021.118049
M3 - Article
SN - 0022-2313
VL - 235
JO - Journal of Luminescence
JF - Journal of Luminescence
M1 - 118049
ER -