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Asymmetrically strained quantum dots with non-fluctuating single-dot emission spectra and subthermal room-temperature linewidths

Abstract

The application of colloidal semiconductor quantum dots as single-dot light sources still requires several challenges to be overcome. Recently, there has been considerable progress in suppressing intensity fluctuations (blinking) by encapsulating an emitting core in a thick protective shell. However, these nanostructures still show considerable fluctuations in both emission energy and linewidth. Here we demonstrate type-I core/shell heterostructures that overcome these deficiencies. They are made by combining wurtzite semiconductors with a large, directionally anisotropic lattice mismatch, which results in strong asymmetric compression of the emitting core. This modifies the structure of band-edge excitonic states and leads to accelerated radiative decay, reduced exciton–phonon interactions, and suppressed coupling to the fluctuating electrostatic environment. As a result, individual asymmetrically strained dots exhibit highly stable emission energy (<1 meV standard deviation) and a subthermal room-temperature linewidth (~20 meV), concurrent with nearly nonblinking behaviour, high emission quantum yields, and a widely tunable emission colour.

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Fig. 1: Asymmetrically strained CdSe/CdxZn1−xSe QDs.
Fig. 2: Spectroscopic analysis of a light–heavy-hole splitting in core/shell CdSe/CdxZn1−xSe QDs (room temperature).
Fig. 3: Photoluminescence dynamics of CdSe/CdxZn1−xSe QDs and CdSe/CdS g-QDs (room temperature).
Fig. 4: Comparison of single-dot spectroscopic characteristics of CdSe/CdxZn1−xSe QDs and reference CdSe/CdS g-QDs (room temperature).
Fig. 5: Analysis of emission linewidths of CdSe/CdxZn1−xSe QDs and reference CdSe/CdS QDs (room temperature).

Data availability

The data that support the findings of this study are available from the authors on reasonable request.

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Acknowledgements

V.I.K. and Y.-S.P. 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. J.L. acknowledges support by the Laboratory Directed Research and Development Program at Los Alamos National Laboratory.

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V.I.K. initiated the study. J.L. developed the synthesis of the asymmetrically strained QDs and fabricated QD samples for this work. Y.-S.P. conducted spectroscopic measurements and analysed the data. V.I.K. and Y.-S.P. prepared the manuscript with input from J.L.

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Correspondence to Victor I. Klimov.

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Supplementary Sections 1,2, Supplementary Figures 1–7, Supplementary Table 1, Supplementary References 1–10

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Park, YS., Lim, J. & Klimov, V.I. Asymmetrically strained quantum dots with non-fluctuating single-dot emission spectra and subthermal room-temperature linewidths. Nature Mater 18, 249–255 (2019). https://doi.org/10.1038/s41563-018-0254-7

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