Synthesis, Structure, Properties, and Application of a Carbazole-Based Diaza[7]helicene in a Deep-Blue-Emitting OLED

Authors

  • Longqiang Shi,

    1. State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
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  • Prof. Dr. Zhi Liu,

    Corresponding author
    1. State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
    • State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
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  • Prof. Dr. Guifang Dong,

    1. Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084 (P.R. China)
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  • Dr. Lian Duan,

    1. Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084 (P.R. China)
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  • Prof. Dr. Yong Qiu,

    1. Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084 (P.R. China)
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  • Dr. Jiong Jia,

    1. School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100 (P.R. China)
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  • Wei Guo,

    1. State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
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  • Dan Zhao,

    1. State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
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  • Prof. Dr. Deliang Cui,

    1. State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
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  • Prof. Dr. Xutang Tao

    1. State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100 (P. R. China), Fax: (+86) 531-8836-2135
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Abstract

A carbazole-based diaza[7]helicene, 2,12-dihexyl-2,12-diaza[7]helicene (1), was synthesized by a photochemical synthesis and its use as a deep-blue dopant emitter in an organic light-emitting diode (OLED) was examined. Compound 1 exhibited good solubility and excellent thermal stability with a high decomposition temperature (Td=372.1 °C) and a high glass-transition temperature (Tg, up to 203.0 °C). Single-crystal structural analysis of the crystalline clathrate (1)2cyclohexane along with a theoretical investigation revealed a non-planar-fused structure of compound 1, which prevented the close-packing of molecules in the solid state and kept the molecule in a good amorphous state, which allowed the optimization of the properties of the OLED. A device with a structure of ITO/NPB (50 nm)/CBP:5 % 1 (30 nm)/BCP (20 nm)/Mg:Ag (100 nm)/Ag (50 nm) showed saturated blue light with Commission Internationale de L’Eclairage (CIE) coordinates of (0.15, 0.10); the maximum luminance efficiency and brightness were 0.22 cd A−1 (0.09 Lm W−1) and 2365 cd m−2, respectively. This new class of helicenes, based on carbazole frameworks, not only opens new possibilities for utilizing helicene derivatives in deep-blue-emitting OLEDs but may also have potential applications in many other fields, such as molecular recognition and organic nonlinear optical materials.

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