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Exciplex-Forming Co-host for Organic Light-Emitting Diodes with Ultimate Efficiency

Authors

  • Young-Seo Park,

    1. Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
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  • Sunghun Lee,

    1. WCU Hybrid Materials Program, Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
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  • Kwon-Hyeon Kim,

    1. WCU Hybrid Materials Program, Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
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  • Sei-Yong Kim,

    1. Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
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  • Jeong-Hwan Lee,

    1. WCU Hybrid Materials Program, Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
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  • Jang-Joo Kim

    Corresponding author
    1. Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
    2. WCU Hybrid Materials Program, Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea
    • Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151-744, South Korea.

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Abstract

Phosphorescent organic light-emitting diodes (OLEDs) with ultimate efficiency in terms of the external quantum efficiency (EQE), driving voltage, and efficiency roll-off are reported, making use of an exciplex-forming co-host. This exciplex-forming co-host system enables efficient singlet and triplet energy transfers from the host exciplex to the phosphorescent dopant because the singlet and triplet energies of the exciplex are almost identical. In addition, the system has low probability of direct trapping of charges at the dopant molecules and no charge-injection barrier from the charge-transport layers to the emitting layer. By combining all these factors, the OLEDs achieve a low turn-on voltage of 2.4 V, a very high EQE of 29.1% and a very high power efficiency of 124 lm W−1. In addition, the OLEDs achieve an extremely low efficiency roll-off. The EQE of the optimized OLED is maintained at more than 27.8%, up to 10 000 cd m−2.

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