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Efficient green InP-based QD-LED by controlling electron injection and leakage

Nature volume 635, pages 854–859 (2024)Cite this article

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Abstract

Green indium phosphide (InP)-based quantum dot light-emitting diodes (QD-LEDs) still suffer from low efficiency and short operational lifetime, posing a critical challenge to fully cadmium-free QD-LED displays and lighting1,2,3. Unfortunately, the factors that underlie these limitations remain unclear and, therefore, no clear device-engineering guidelines are available. Here, by using electrically excited transient absorption spectroscopy, we find that the low efficiency of state-of-the-art green cadmium-free QD-LEDs (which ubiquitously adopt the InP–ZnSeS–ZnS core–shell–shell structure) originates from the ZnSeS interlayer because it imposes a high injection barrier that limits the electron concentration and trap saturation. We demonstrate, both experimentally and theoretically, that replacing the currently widely used ZnSeS interlayer with a thickened ZnSe interlayer enables improved electron injection and depressed leakage simultaneously, allowing to achieve a peak external quantum efficiency of 26.68% and T95 lifetime (time for the luminance to drop to 95% of the initial value) of 1,241 h at an initial brightness of 1,000 cd m–2 in green InP-based QD-LEDs emitting at 543 nm—exceeding the previous best values by a factor of 1.6 and 165, respectively3,4.

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Fig. 1: EETA spectroscopy.
Fig. 2: Strategies to improve the EQE of green InP-based QD-LEDs.
Fig. 3: Tunnelling model of electron injection and leakage in QD-LEDs.
Fig. 4: Characterization of high-performance InP–thick ZnSe–ZnS QD-LEDs.

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Data availability

The data that support the findings of this study are available in the article and its Supplementary Information. All other relevant data are available from the corresponding authors upon reasonable request. Additional data are available on Figshare at https://doi.org/10.6084/m9.figshare.27682983 (ref. 43). Source data are provided with this paper.

Code availability

The code that supports the findings of this study is available from the corresponding authors upon reasonable request.

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Acknowledgements

We acknowledge financial support from the National Natural Science Foundation of China (grant nos. U22A2072, 52272167 and 62204078), Innovation Program for Quantum Science and Technology (grant no. 2021ZD0301603), Fundamental Research Funds for the Central Universities, the National Key R&D Program of China (grant nos. 2023YFE0205000 and 2022YFB3602901), Zhongyuan High Level Talents Special Support Plan (grant no. 244200510009), the Beijing Natural Science Foundation (grant no. Z220007) and the Postdoctoral Fellowship Program (Grade C) of the China Postdoctoral Science Foundation (grant no. GZC20240386).

Author information

Author notes

  1. These authors contributed equally: Yangyang Bian, Xiaohan Yan

Authors and Affiliations

  1. Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, Henan University, Kaifeng, China

    Yangyang Bian, Fei Chen, Qian Li, Han Zhang, Wenjing Zhang, Dandan Zhang & Huaibin Shen

  2. CAS Key Laboratory of Microscale Magnetic Resonance, School of Physical Sciences, Hefei National Laboratory, and Anhui Province Key Laboratory of Scientific Instrument Development and Application, University of Science and Technology of China, Hefei, China

    Yangyang Bian, Xiaohan Yan, Bo Li & Fengjia Fan

  3. Key Laboratory of Luminescence and Optical Information, Ministry of Education, School of Physical Science and Engineering, Beijing Jiaotong University, Beijing, China

    Yangyang Bian, Shuaibing Wang & Aiwei Tang

  4. TCL Corporate Research, Shenzhen, China

    Wenjun Hou & Zizhe Lu

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Contributions

F.F. and H.S. conceived the concept and designed the experiments. H.S., F.F., A.T. and F.C. supervised the project. Y.B. and X.Y. contributed equally. Y.B. and Q.L. synthesized the materials. F.C., S.W., H.Z., W.Z. and D.Z. fabricated the devices and collected the performance data of the QD-LEDs. X.Y. conducted the EETA experiments and developed the tunnelling model. Z.L. and W.H. collected the operational lifetime data of the QD-LEDs. Y.B., X.Y., F.C., B.L., F.F. and H.S. conducted the data analysis and wrote the manuscript. All authors contributed to the scientific discussion and modified the manuscript.

Corresponding authors

Correspondence to Fei Chen, Aiwei Tang, Fengjia Fan or Huaibin Shen.

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The authors declare no competing interests.

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Nature thanks Eunjoo Jang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data figures and tables

Extended Data Fig. 1 PETA and EETA spectra of Cd-based QD-LEDs.

PETA spectra of QD-LEDs based on (a) 636 nm (ZnCdSe/ZnSeS), (b) 529 nm (CdSeS/ZnSe/ZnS) and (c) 473 nm (ZnCdSe/ZnSe/ZnS) core/shell QDs. EETA spectra of QD-LEDs based on (d) 636 nm (ZnCdSe/ZnSeS), (e) 529 nm (CdSeS/ZnSe/ZnS) and (f) 473 nm (ZnCdSe/ZnSe/ZnS) core/shell QDs.

Source Data

Extended Data Fig. 2 Characterizations of high-performance QD-LEDs based on 636 nm, 529 nm and 473 nm Cd-based QDs.

a, d, g, Current density-luminance-voltage (J–L–V) characteristics. b, e, h, EQE and current efficiency (ηA) as functions of luminance for those devices. c, f, i, EL spectra versus voltage profiles.

Source Data

Extended Data Fig. 3 PETA and EETA spectra on InP-based QD-LEDs.

PETA spectra of QD-LEDs based on (a) 615 nm, (c) 593 nm, (e) 560 nm and (g) 540 nm InP/ZnSeS/ZnS core/shell QDs. EETA spectra of QD-LEDs based on (b) 615 nm, (d) 593 nm, (f) 560 nm and (h) 540 nm InP/ZnSeS/ZnS core/shell QDs.

Source Data

Extended Data Fig. 4 Characterizations of QD-LEDs based on 615 nm and 540 nm InP/ZnSeS/ZnS QDs.

a, d, J–L–V characteristics. b, e, EQE and ηA as functions of luminance for those devices. c, f, EL spectra versus voltage profiles.

Source Data

Extended Data Fig. 5 Characterizations of InP/ZnSeS/ZnS QDs and InP-based QD-LEDs with different ZnS proportions in the ZnSeS interlayer shell.

a, Absorbance and PL spectra. b, FWHM (left axis) and PL QY (right axis). c, X-ray diffraction pattern. d, J–L–V characteristics. e, EQE and ηA as functions of luminance for those devices.

Source Data

Extended Data Fig. 6 Characterizations of InP/ZnSe/ZnS QDs and QD-LEDs with different ZnSe thicknesses.

a, Absorbance and PL spectra. b, FWHM (left axis) and PL QY (right axis). c, X-ray diffraction pattern. TEM images of InP/ZnSe/ZnS QDs with different ZnSe thicknesses (2.5 nm, 3.3 nm, 4.0 nm, 4.5 nm). e, J–L–V characteristics. f, EQE and ηA as functions of luminance for those devices.

Source Data

Extended Data Fig. 7 Comparison of our device with previously reported high-performance green InP-based QD-LEDs in terms of EQE, luminance and lifetime.

a, Comparison of EQE with previously reported values. b, Comparison of luminance with previously reported values. Comparison of (c) T50@100 cd m−2 and (d) T95@100 cd m−2 lifetime with previously reported values. Data are taken from refs. 3,4,14,27,28,29,31,32,33,34,35,37,38,44,45.

Source Data

Extended Data Fig. 8 Operational lifetimes characterizations of QD-LEDs.

The operational lifetimes (actual luminance/initial luminance (L/L0) versus time) of QD-LEDs based on (a) InP/ZnSeS/ZnS, (b) InP/ZnSe (2.5 nm)/ZnS, (c) InP/ZnSe (3.3 nm)/ZnS and (d) InP/ZnSe (4.5 nm)/ZnS. The lifetimes (T95) at various initial luminance (L0) values are shown in the insets. The acceleration factors (n) are fitted according to the empirical relationship of L0n • T = constant.

Source Data

Extended Data Table 1 Comparison of our device with previously reported high-performance green Cd-free based QD-LEDs in terms of EQE and luminance
Full size table
Extended Data Table 2 Comparison of our device with previously reported high-performance green Cd-free based QD-LEDs in terms of lifetime
Full size table

Supplementary information

Supplementary Information

Supplementary Figs. 1–14 and Tables 1–6.

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Bian, Y., Yan, X., Chen, F. et al. Efficient green InP-based QD-LED by controlling electron injection and leakage. Nature 635, 854–859 (2024). https://doi.org/10.1038/s41586-024-08197-z

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