Colloidal semiconductor quantum dots are robust emitters implemented in numerous prototype and commercial optoelectronic devices. However, active fluorescence colour tuning, achieved so far by electric-field-induced Stark effect, has been limited to a small spectral range, and accompanied by intensity reduction due to the electron–hole charge separation effect. Utilizing quantum dot molecules that manifest two coupled emission centres, we present a unique electric-field-induced instantaneous colour-switching effect. Reversible emission colour switching without intensity loss is achieved on a single-particle level, as corroborated by correlated electron microscopy imaging. Simulations establish that this is due to the electron wavefunction toggling between the two centres, induced by the electric field, and affected by the coupling strength. Quantum dot molecules manifesting two coupled emission centres may be tailored to emit distinct colours, opening the path for sensitive field sensing and colour-switchable devices such as a novel pixel design for displays or an electric-field-induced colour-tunable single-photon source.
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The home-written MATLAB code used for the analysis of the measurements performed is not deemed central to the conclusions, and follows spectral analysis standards of the field (and previous works). It is available from the corresponding author upon reasonable request.
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The study has received financial support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project CoupledNC, grant agreement no. ; project CQDplay, grant agreement no. ) (U.B., Y.O., A.L., Y.E.P., E.S., N.C. and S.K.). Y.O. and E.S. acknowledge support from the Hebrew University Center for Nanoscience and Technology. Y.E.P. acknowledges support from the Ministry of Science and Technology and the National Foundation for Applied and Engineering Sciences, Israel. S.K. acknowledges support from the Planning and Budgeting Committee of the higher board of education in Israel through a fellowship. U.B. thanks the Alfred & Erica Larisch memorial chair. We thank G. Chechelinsky, M. Saidian, I. Shweki and S. Eliav from the Unit for Nano Characterization (UNC) of the Hebrew University of Jerusalem, Center for Nanoscience and Nanotechnology, for assistance in the electrode device fabrication. We thank S. Gigi for helpful discussions.
The authors declare no competing interests.
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Supplementary Figs. 1–31, Text 1 (on self-consistent effective mass calculations), Table 1 and captions for Videos 1–3.
Step-by-step lift out and TEM grid preparation (using the SEM–dual-beam FIB system).
Raw measurement of PL emission wavelength on the EMCCD of the CQDM (Figs. 1c and 2), with periodic EF modulation from +180 to 0 V at 10 Hz rate.
Measurement of PL emission wavelength on the EMCCD of the CQDM (Fig. 6a and Supplementary Fig. 26) with periodic EF modulation between +180 and −180 V at 10 Hz rate.
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Ossia, Y., Levi, A., Panfil, Y.E. et al. Electric-field-induced colour switching in colloidal quantum dot molecules at room temperature. Nat. Mater. 22, 1210–1217 (2023). https://doi.org/10.1038/s41563-023-01606-0