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Efficient and stable one-micrometre-thick organic light-emitting diodes

Nature Photonics volume 16, pages 876–883 (2022)Cite this article

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Abstract

Organic light-emitting diodes (OLEDs) with thick carrier transport layers are desirable for high production yields of OLED-based displays and lighting; however, high operating voltages are inevitably introduced to thick OLEDs due to the low carrier mobilities of organics. The associated Joule heating will also induce structural defects and lower operational stabilities. Here we demonstrate highly efficient and stable OLEDs with thicknesses of over 1 μm and low operating voltages. The OLEDs use MoO3/SimCP2 as a hole-injection layer and a thick layer of 4,4′-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline) (TAPC) as a hole-transporting layer. We find that Ohmic hole injection can only be formed for TAPC layers with thicknesses of over 900 nm. In this configuration, we achieve external quantum efficiencies of 23.09%, 22.19% and 7.39%, and operating voltages of 5.11 V, 3.55 V and 6.88 V at 1,000 cd cm–2 for red, green and blue OLEDs, respectively. We also incorporate a thin layer of HAT-CN between the TAPC and electron-blocking layers to suppress electron leakage. The red, green and blue OLEDs in this work maintained the above-mentioned performances while also featuring excellent extrapolated LT95 operational lifetimes of around 55,000 h, 18,000 h and 1,600 h, respectively, at an initial luminance of 1,000 cd cm–2. We believe that our work paves the way for large-area OLED-based displays and lighting with high production yields.

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Fig. 1: Excellent electrical properties of MoO3/SimCP2 layer.
Fig. 2: Thickness dependence of electroluminescence characteristics of the red, green and blue OLEDs.
Fig. 3: Device characteristics of thick red, green and blue OLEDs with 950-nm-thick layers of TAPC.
Fig. 4: Long-term operational stability of the thick red, green and blue OLEDs with a HAT-CN interlayer.

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

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Acknowledgements

This work was funded by National Natural Science Foundation of China (grant no. 21772209), International Partnership Program of Chinese Academy of Sciences (IPP) (grant no. 1A1111KYSB20210028) and National Program for Support of Top-notch Young Professionals. We also thank R. Jin and G. Cui (Chemistry College, Beijing Normal University) for their kind help with the calculation of anionic bond dissociation energies.

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Author notes

  1. These authors contributed equally: Guanhao Liu, Zhiyi Li.

Authors and Affiliations

  1. Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU−CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China

    Guanhao Liu, Zhiyi Li, Xiaoxiao Hu, Yuanyuan Qin, Pengfei Wang & Ying Wang

  2. University of Chinese Academy of Sciences, Beijing, China

    Guanhao Liu, Zhiyi Li, Xiaoxiao Hu, Yuanyuan Qin, Pengfei Wang & Ying Wang

  3. Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, China

    Chun-Sing Lee

  4. MoE Key Laboratory of Photoelectronic Imaging Technology and System, School of Optics and Photonics, Beijing Institute of Technology, Beijing, China

    Dongqi Chen & Lingxue Wang

  5. Center for Emergent Matter Science (CEMS), RIKEN, Wako, Japan

    Jianjun Liu & Yong-Jin Pu

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Contributions

Y. W., P. F. W., G. H. L and Z. Y. L. conceived the concepts. G. H. L and Z. Y. L fabricated the devices and performed the measurement. Y. Y. Q conducted the calculation of bond dissociation energy. X. X. H synthesized and purified materials. L. X. W. and D. Q. C. conceived the optical simulation. J. J. L and Y. J. P performed angular-dependent measurements. Y. W., G. H. L. and C.-S. L. contributed to the writing of the manuscript and to discussion of the results.

Corresponding authors

Correspondence to Pengfei Wang or Ying Wang.

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Nature Photonics thanks Qin Chuanjiang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–31, Tables 1–3 and refs.1–9.

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Liu, G., Li, Z., Hu, X. et al. Efficient and stable one-micrometre-thick organic light-emitting diodes. Nat. Photon. 16, 876–883 (2022). https://doi.org/10.1038/s41566-022-01084-x

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