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Tuning Energy Levels of Electron-Transport Materials by Nitrogen Orientation for Electrophosphorescent Devices with an ‘Ideal’ Operating Voltage

Authors

  • Shi-Jian Su,

    Corresponding author
    1. Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640 (P. R. China)
    2. Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo 112-0014 (Japan)
    • Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640 (P. R. China)
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  • Hisahiro Sasabe,

    1. Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo 112-0014 (Japan)
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  • Yong-Jin Pu,

    1. Department of Organic Device Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510 (Japan)
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  • Ken-ichi Nakayama,

    1. Department of Organic Device Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510 (Japan)
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  • Junji Kido

    Corresponding author
    1. Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo 112-0014 (Japan)
    2. Department of Organic Device Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510 (Japan)
    • Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo 112-0014 (Japan).
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Abstract

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A series of 1,3,5-triazine-core-containing electron-transport materials (ETMs) are reported as an undoped electron-transport layer (ETL), whose energy levels can be tuned by introducing pyridine rings on the periphery of the molecule and also orientation of nitrogen. An unprecedented low operating voltage of 2.42 V, corresponding to the emitting photon energy (hv), was achieved for the fac-tris(2-phenylpyridine) iridium (Ir(PPy)3) based green phosphorescent OLEDs at 100 cd m−2 without consumption of their efficiency. Moreover, the threshold voltage for electroluminescence can be even 0.1 ∼ 0.2 V lower than the minimum value of hv/e.

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