The availability of colloidal quantum dots with highly efficient, fast and ‘non-blinking’ near-infrared emission would benefit numerous applications, from advanced optical communication and quantum networks to biomedical diagnostics. Here, we report high-quality near-infrared emitters that are based on well known CdSe/CdS heterostructures. By incorporating an HgS interlayer at the quantum dot core/shell interface, we convert normally visible emitters into highly efficient near-infrared fluorophores. Employing thermodynamically controlled sequential deposition of metal and chalcogen ions, we achieve atomic-level precision in defining the thickness of the HgS interlayer (H). This manifests in ‘quantized’ jumps of the photoluminescence spectrum when H changes in discrete, atomic steps. The synthesized structures show highly efficient photoluminescence, tunable from 700 to 1,370 nm, and fast radiative rates of ~1/60 ns−1. The emission from individual CdSe/HgS/CdS colloidal quantum dots is virtually blinking free and exhibits nearly perfect single-photon purity. In addition, when incorporated into a light-emitting-diode architecture, these quantum dots demonstrate strong electroluminescence with a sub-bandgap turn-on voltage.
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Syntheses of the CdSe/HgS/CdS CQDs, modelling of their electronic states, single-dot spectroscopic studies and research into CQD LEDs were supported by the Laboratory Directed Research and Development (LDRD) programme at Los Alamos National Laboratory under project 20200213DR. Time-resolved optical-spectroscopy studies of the CdSe/HgS/CdS CQDs were supported by the Solar Photochemistry Program of the Chemical Sciences, Biosciences and Geosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy. We thank H. Jin for TEM measurements and K. Velizhanin for help with the code used in calculations of electronic states.
The authors declare no competing interests.
Peer review information Nature Nanotechnology thanks Sohee Jeong and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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c, XRD patterns of CdSeWZ/mHgS/2CdS CQDs as a function of m. d, Evolution of size distribution of CdSe/mHgS CQDs for m = 0–3. e, Gaussian fits of CdSe/mHgS CQD size distributions for m = 0–3.
a, Evolution of PL spectra of CdSeWZ/mHgS/2CdS CQDs (m = 1–3). b, Two levels of control of the PL spectral energy of CdSe/HgS/CdS CQDs. c, Evolution of absorption and PL spectra of CdSeZB/1HgS/nCdS (n = 0, 2, 6). d, CB and VB confinement potentials in CdSe/2HgS/2CdS CQDs. e, The measured 1S-peak absorption, PL energies and calculated 1Sh–1Se transition energy of the CdSeZB/mHgS/2CdS CQDs. f, The measured and the calculated 1Se–1Sh transition energies.
a, PL intensity versus time for CdSe/1HgS/2CdS. b, PL intensity versus time for CdSe/1HgS/6CdS. c, Single-exciton PL dynamics of a CdSe/1HgS/6CdS CQD. d, A time-dependent g(2) function. e, A CQD ensemble and single-dot PL spectra.
b, Current/radiance of LED. c, EQE/PCE of LED.
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Sayevich, V., Robinson, Z.L., Kim, Y. et al. Highly versatile near-infrared emitters based on an atomically defined HgS interlayer embedded into a CdSe/CdS quantum dot. Nat. Nanotechnol. 16, 673–679 (2021). https://doi.org/10.1038/s41565-021-00871-x
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