Optimizing the Charge Balance of Fluorescent Organic Light-Emitting Devices to Achieve High External Quantum Efficiency Beyond the Conventional Upper Limit

Authors

  • Yong-Jin Pu,

    Corresponding author
    1. Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
    • Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan.
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  • Go Nakata,

    1. Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
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  • Fumiya Satoh,

    1. Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
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  • Hisahiro Sasabe,

    1. Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
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  • Daisuke Yokoyama,

    1. Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
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  • Junji Kido

    Corresponding author
    1. Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
    • Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Yamagata 992-8510, Japan.
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Abstract

original image

The external quantum efficiencies (EQEs) of fluorescent light emitting devices are drastically improved by optimizing the charge balance. When N,N′-di(naphthalene-1-yl)- N,N′-diphenylbenzidine (NPD) is used as a hole-transporting layer (HTL) and Alq3 as an electron-transporting layer (ETL) with the green dopant 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-10-(2-benzothiazolyl)quinolizino-[9,9a,1gh]coumarin (C545T), the EQE is observed to be approximately 3%. However, when the HTL and ETL materials are optimized, a 7.5% external quantum efficiency (EQE) in a green-emitting device and an 8.2% EQE in a blue-emitting device are achieved at 100 cd m−2.

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