Quantum dot solids showing state-resolved band-like transport

Abstract

Improving charge mobility in quantum dot (QD) films is important for the performance of photodetectors, solar cells and light-emitting diodes. However, these applications also require preservation of well defined QD electronic states and optical transitions. Here, we present HgTe QD films that show high mobility for charges transported through discrete QD states. A hybrid surface passivation process efficiently eliminates surface states, provides tunable air-stable n and p doping and enables hysteresis-free filling of QD states evidenced by strong conductance modulation. QD films dried at room temperature without any post-treatments exhibit mobility up to μ ~ 8 cm2 V−1 s−1 at a low carrier density of less than one electron per QD, band-like behaviour down to 77 K, and similar drift and Hall mobilities at all temperatures. This unprecedented set of electronic properties raises important questions about the delocalization and hopping mechanisms for transport in QD solids, and introduces opportunities for improving QD technologies.

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Fig. 1: HgTe QDs.
Fig. 2: State filling in HgTe QD FETs.
Fig. 3: Charge transport studies of 13.1 ± 1.1 nm HgTe QD solids.
Fig. 4: Hall effect, Seebeck effect and photoconductivity of HgTe QD films.

Data availability

The data sets generated and analysed during the current study are available from the corresponding author on reasonable request. Source data for Figs. 1–4 are provided with the paper.

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Acknowledgements

This work was supported by the University of Chicago Materials Research Science and Engineering Center, which is funded by the NSF under award number DMR-1420709, by the Defense Advanced Research Projects Agency (DARPA) as a subcontract to Voxtel, Inc. for the Wired program, by the Department of Defense (DOD) Air Force Office of Scientific Research under grant number FA9550-18-1-0099 and by the National Science Foundation under grant DMR-1708378.

Author information

M.H.H. carried out experiments on QD synthesis. X.L. and Y.W. developed the methods for ligands exchange. V.K. carried out SAXS measurements and data analysis. X.L. and M.C. prepared thin-film devices and carried out charge-transport experiments. X.L., M.C., P.G.-S. and D.V.T. performed the analysis of the transport data. The manuscript was written by D.V.T. and P.G.-S. All the authors discussed the results and commented on the manuscript.

Correspondence to Philippe Guyot-Sionnest or Dmitri V. Talapin.

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Supplementary information

Supplementary Information

Supplementary materials and methods, Discussion 1–10, Tables 1–5 and Figs. 1–19.

Source data

Source Data Fig. 1

Unprocessed Fourier-transform infrared absorption spectra of undoped and n-type doped 12.5 ± 1.0 nm HgTe QDs and fitting. SAXS data and fitting.

Source Data Fig. 2

Unprocessed FET transport data of HgTe and intraband spectra.

Source Data Fig. 3

Mobility as a function of temperature.

Source Data Fig. 4

Hall voltage, Seebeck coefficient, Hall mobility and FET mobility at different temperatures. Photoresponse data.

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Lan, X., Chen, M., Hudson, M.H. et al. Quantum dot solids showing state-resolved band-like transport. Nat. Mater. (2020). https://doi.org/10.1038/s41563-019-0582-2

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