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Synthesis, Photophysical, and Electroluminescent Device Properties of Zn(II)-Chelated Complexes Based on Functionalized Benzothiazole Derivatives

Authors

  • Soo-Gyun Roh,

    1. Department of Advanced Materials Chemistry and Center for Advanced Photovoltaic Materials Korea University ChungNam 339-700 (Korea)
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  • Yong-Hee Kim,

    1. Department of Advanced Materials Chemistry and Center for Advanced Photovoltaic Materials Korea University ChungNam 339-700 (Korea)
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  • Kang Deuk Seo,

    1. Department of Advanced Materials Chemistry and Center for Advanced Photovoltaic Materials Korea University ChungNam 339-700 (Korea)
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  • Dong Hyun Lee,

    1. Department of Advanced Materials Chemistry and Center for Advanced Photovoltaic Materials Korea University ChungNam 339-700 (Korea)
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  • Hwan Kyu Kim,

    Corresponding author
    1. Department of Advanced Materials Chemistry and Center for Advanced Photovoltaic Materials Korea University ChungNam 339-700 (Korea)
    • Department of Advanced Materials Chemistry and Center for Advanced Photovoltaic Materials Korea University ChungNam 339-700 (Korea).
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  • Young-Il Park,

    1. Department of Chemistry Display Research Center The Catholic University of Korea Bucheon 420-734 (Korea)
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  • Jong-Wook Park,

    1. Department of Chemistry Display Research Center The Catholic University of Korea Bucheon 420-734 (Korea)
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  • Ji-Hoon Lee

    Corresponding author
    1. Department of Polymer Science and Engineering and Photovoltaic Technology Institute Chungju National University Chungju 308-702 (Korea)
    • Department of Polymer Science and Engineering and Photovoltaic Technology Institute Chungju National University Chungju 308-702 (Korea).
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Abstract

New Zn(II)-chelated complexes based on benzothiazole derivatives, including substituted functional groups such as methyl (MeZn), methoxy (MeOZn), or fluorenyl unit (FuZn), are investigated to produce white-light emission. 2-(2-Hydroxyphenyl)benzothiazole derivatives in toluene and DMSO exhibit excited-state intramolecular proton transfer (ESIPT), leading to a large Stokes shift of the fluorescence emission. However, in methanol they exhibit no ESIPT due to the intermolecular hydrogen bonding between the 2-(2-hydroxyphenyl)benzothiazole derivative and methanol. Their Zn(II)-chelated complexes exhibit the absorption band red-shifted at 500 nm in nonpolar solvent and the absorption band blue-shifted at about 420 nm in protic solvent. In multilayer electroluminescent devices, methyl-substituted Zn(II)-chelated complex (MeZn) exhibits excellent power efficiency and fluorene-substituted Zn(II)-chelated complex (FuZn) has a high luminance efficiency (1 cd m−2 at 3.5 V, 10 400 cd m−2 at 14 V). The EL spectra of Zn(II)-chelated complexes based on benzothiazole derivatives exhibit broad emission bands. In addition, their electron-transport property for red–green–blue (RGB) organic light-emitting diodes (OLEDs) is systematically studied, in comparison with that of Alq3. The results demonstrate the promising potential of MeZn as an electron-transporting layer (ETL) material in preference to Alq3, which is widely used as an ETL material.

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