Highly Efficient Electron-Transporting/Injecting and Thermally Stable Naphthyridines for Organic Electrophosphorescent Devices

Authors

  • Lixin Xiao,

    Corresponding author
    1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
    • State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
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  • Xing Xing,

    1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
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  • Zhijian Chen,

    1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
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  • Bo Qu,

    1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
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  • Hsinglin Lan,

    1. Department of Organic Device Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
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  • Qihuang Gong,

    Corresponding author
    1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
    • State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
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  • Junji Kido

    Corresponding author
    1. Department of Organic Device Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan, Optoelectronic Industry and Technology Development Association, (OITDA), 1-20-10 Sekiguchi, Bunkyo-ku, Tokyo 112-0014, Japan
    • Department of Organic Device Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan, Optoelectronic Industry and Technology Development Association, (OITDA), 1-20-10 Sekiguchi, Bunkyo-ku, Tokyo 112-0014, Japan.
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Abstract

A series of 1,8-naphthyridine derivatives is synthesized and their electron-transporting/injecting (ET/EI) properties are investigated via a multilayered electrophosphorescent organic light-emitting device (OLED) using fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] as a green phosphorescent emitter doped into a 4,4′-N,N′-dicarbazolebiphenyl (CBP) host with 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (a-NPD) as the hole-transporting layer, and poly(arylene ether sulfone) containing tetraphenylbenzidine (TPDPES) doped with tris(4-bromophenyl)ammonium hexachloroantimonate (TBPAH) as the hole-injecting layer. The turn-on voltage of the device is 2.5 V using 2,7-bis[3-(2-phenyl)-1,8-naphthyridinyl]-9,9-dimethylfluorene (DNPF), lower than that of 3.0 V for the device using a conventional ET material. The maximum current efficiency (CE) and power efficiency (PE) of the DNPF device are much higher than those of a conventional device. With the aid of a hole-blocking (HB) and exciton-blocking layer of bathocuproine (BCP), 13.2–13.7% of the maximum external quantum efficiency (EQE) and a maximum PE of 50.2–54.5 lm W−1 are obtained using the naphthyridine derivatives; these values are comparable with or even higher than the 13.6% for conventional ET material. The naphthyridine derivatives show high thermal stabilities, glass-transition temperatures much higher than that of aluminum(III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (BAlq), and decomposition temperatures of 510–518 °C, comparable to or even higher than those of Alq3.

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