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High-efficiency quantum-dot light-emitting devices with enhanced charge injection

Abstract

We report a colour-saturated, red quantum-dot light-emitting device (QLED) using an inverted organic–inorganic hybrid device structure and colloidal CdSe–CdS (core–shell) quantum-dot emitters. The strong electronic coupling of quantum dots to an adjacent layer of ZnO nanocrystals (which form the electron transport layer) facilitates charge transfer, which is responsible for both injecting electrons and maintaining an optimal charge balance for the quantum dot emitters. We show that QLED performance can be modified by controlling the distance of the electroluminescence recombination zone within the quantum dot film from the quantum dot–ZnO interface. Devices are reported with a luminous efficiency of 19 cd A−1, corresponding to an external quantum efficiency of 18% (which is close to the theoretical maximum of 20%) and an internal quantum efficiency of 90%. The corresponding luminous power efficiency exceeds 25 lm W−1 due to the low operating voltage of the device.

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Figure 1: Energy diagram and emission spectrum of high-efficiency QLEDs.
Figure 2: Luminous power efficiency, current–voltage behaviour and EQE measurements of QLEDs.
Figure 3: Luminance and current efficiency performance of QLEDs.
Figure 4: Simultaneous measurements of electroluminescence and photoluminescence as a function of time.
Figure 5: Kelvin probe measurement of the evolution of surface potential over time.

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Acknowledgements

The authors would like to thank W. Tisdale (MIT) for collecting the transient photoluminescence data.

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Authors

Contributions

B.S.M. and P.T.K. conceived the device and study design. B.S.M., M.S., Z.P. and Z.Z. fabricated and characterized devices. C.H. synthesized the quantum dots. P.T.K. supervised the study. All authors contributed to the analysis and interpretation of results and writing the paper.

Corresponding author

Correspondence to Peter T. Kazlas.

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The authors declare no competing financial interests.

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Mashford, B., Stevenson, M., Popovic, Z. et al. High-efficiency quantum-dot light-emitting devices with enhanced charge injection. Nature Photon 7, 407–412 (2013). https://doi.org/10.1038/nphoton.2013.70

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