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Highly efficient blue electroluminescence based on thermally activated delayed fluorescence

Nature Materials volume 14, pages 330–336 (2015)Cite this article

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Abstract

Organic compounds that exhibit highly efficient, stable blue emission are required to realize inexpensive organic light-emitting diodes for future displays and lighting applications. Here, we define the design rules for increasing the electroluminescence efficiency of blue-emitting organic molecules that exhibit thermally activated delayed fluorescence. We show that a large delocalization of the highest occupied molecular orbital and lowest unoccupied molecular orbital in these charge-transfer compounds enhances the rate of radiative decay considerably by inducing a large oscillator strength even when there is a small overlap between the two wavefunctions. A compound based on our design principles exhibited a high rate of fluorescence decay and efficient up-conversion of triplet excitons into singlet excited states, leading to both photoluminescence and internal electroluminescence quantum yields of nearly 100%.

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Figure 1: Chemical structures and distribution of HOMO and LUMO in 1a, 2a, 2b and 2c.
Figure 2: Photoluminescence processes of 1a (top) and 2a (bottom).
Figure 3: Electroluminescence characteristics of OLEDs using emitter layers containing 1a and 2a–c as guests and photoluminescence characteristics of the emitter layers.

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Acknowledgements

This work was supported in part by the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) and the International Institute for Carbon Neutral Energy Research (WPI-I2CNER) sponsored by MEXT. The authors thank K. Tokumaru for stimulating discussions regarding this work. The authors also thank W. J. Potscavage Jr for assistance with preparation of this manuscript.

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Authors and Affiliations

  1. Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan

    Shuzo Hirata, Yumi Sakai, Kensuke Masui, Hiroyuki Tanaka, Sae Youn Lee, Hiroko Nomura, Nozomi Nakamura, Mao Yasumatsu, Hajime Nakanotani, Qisheng Zhang, Katsuyuki Shizu, Hiroshi Miyazaki & Chihaya Adachi

  2. Research & Development Department, Dyden Corporation, 1-1 Hyakunenkouen, Kurume, Fukuoka 839-0864, Japan

    Yumi Sakai

  3. Advanced Core Technology Laboratories, Fujifilm Corporation, 577 Ushijima, Kaisei, Ashigarakami, Kanagawa 258-8577, Japan

    Kensuke Masui

  4. JST, ERATO, Adachi Molecular Exciton Engineering Project, 744 Motooka, Nishi, Fukuoka 819-0395, Japan

    Sae Youn Lee, Hajime Nakanotani, Qisheng Zhang, Katsuyuki Shizu & Chihaya Adachi

  5. Innovative Organic Device Laboratory, Institute of Systems, Information Technologies and Nanotechnologies (ISIT), 744 Motooka, Nishi Fukuoka 819-0395, Japan,

    Hajime Nakanotani

  6. Nippon Steel & Sumikin Chemical Co. Ltd., 46-80, Nakabaru Sakinohama, Tobata, Kitakyushu 804-8503, Japan

    Hiroshi Miyazaki

  7. International Institute for Carbon Neutral Energy Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan

    Chihaya Adachi

Authors
  1. Shuzo Hirata
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Contributions

S.H. and C.A. wrote the manuscript. S.H. proposed the delocalization of molecular orbitals and designed the compounds. S.H., Y.S. and H.T. synthesized the compounds. K.S. helped with calculations and S.Y.L., H.N. and N.N. helped with purification of the compounds. S.H. and K.M. fabricated devices with the aid of M.Y. and H.N. S.H., K.S. and K.M. measured photophysical characteristics. S.H. and Y.S. performed analyses. C.A. supervised TADF research. All authors discussed the progress of research and reviewed the manuscript.

Corresponding author

Correspondence to Chihaya Adachi.

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The authors declare no competing financial interests.

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Hirata, S., Sakai, Y., Masui, K. et al. Highly efficient blue electroluminescence based on thermally activated delayed fluorescence. Nature Mater 14, 330–336 (2015). https://doi.org/10.1038/nmat4154

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