2,5-Difluorenyl-Substituted Siloles for the Fabrication of High-Performance Yellow Organic Light-Emitting Diodes

Authors

  • Bin Chen,

    1. College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China)
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  • Yibin Jiang,

    1. Center for Display Research, The Hong Kong University of Science & Technology (HKUST), Kowloon, Hong Kong (China)
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  • Long Chen,

    1. Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)
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  • Han Nie,

    1. Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)
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  • Bairong He,

    1. College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China)
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  • Dr. Ping Lu,

    1. State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012 (China)
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  • Herman H. Y. Sung,

    1. Department of Chemistry, Division of Biomedical Engineering, Institute for Advanced Study and Institute of Molecular Functional Materials, HKUST, Kowloon, Hong Kong (China)
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  • Prof. Ian D. Williams,

    1. Department of Chemistry, Division of Biomedical Engineering, Institute for Advanced Study and Institute of Molecular Functional Materials, HKUST, Kowloon, Hong Kong (China)
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  • Prof. Hoi Sing Kwok,

    1. Center for Display Research, The Hong Kong University of Science & Technology (HKUST), Kowloon, Hong Kong (China)
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  • Prof. Anjun Qin,

    1. Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)
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  • Prof. Zujin Zhao ,

    Corresponding author
    1. College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China)
    2. Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)
    • Zujin Zhao , College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China)

      Ben Zhong Tang , Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)

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  • Prof. Ben Zhong Tang 

    Corresponding author
    1. Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)
    2. Department of Chemistry, Division of Biomedical Engineering, Institute for Advanced Study and Institute of Molecular Functional Materials, HKUST, Kowloon, Hong Kong (China)
    • Zujin Zhao , College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036 (China)

      Ben Zhong Tang , Center for Display Research, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)

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Abstract

2,3,4,5-Tetraarylsiloles are a class of important luminogenic materials with efficient solid-state emission and excellent electron-transport capacity. However, those exhibiting outstanding electroluminescence properties are still rare. In this work, bulky 9,9-dimethylfluorenyl, 9,9-diphenylfluorenyl, and 9,9′-spirobifluorenyl substituents were introduced into the 2,5-positions of silole rings. The resulting 2,5-difluorenyl-substituted siloles are thermally stable and have low-lying LUMO energy levels. Crystallographic analysis revealed that intramolecular π–π interactions are prone to form between 9,9′-spirobifluorene units and phenyl rings at the 3,4-positions of the silole ring. In the solution state, these new siloles show weak blue and green emission bands, arising from the fluorenyl groups and silole rings with a certain extension of π conjugation, respectively. With increasing substituent volume, intramolecular rotation is decreased, and thus the emissions of the present siloles gradually improved and they showed higher fluorescence quantum yields (ΦF=2.5–5.4 %) than 2,3,4,5-tetraphenylsiloles. They are highly emissive in solid films, with dominant green to yellow emissions and good solid-state ΦF values (75–88 %). Efficient organic light-emitting diodes were fabricated by adopting them as host emitters and gave high luminance, current efficiency, and power efficiency of up to 44 100 cd m−2, 18.3 cd A−1, and 15.7 lm W−1, respectively. Notably, a maximum external quantum efficiency of 5.5 % was achieved in an optimized device.

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