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Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence

Nature Photonics volume 8, pages 326–332 (2014)Cite this article

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Abstract

Organic light-emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) have emerged as cheaper alternatives to high-performance phosphorescent OLEDs with noble-metal-based dopants. However, the efficiencies of blue TADF OLEDs are still low at high luminance, limiting full-colour display. Here, we report a blue OLED containing a 9,10-dihydroacridine/diphenylsulphone derivative that has a comparable performance to today's best phosphorescent OLEDs. The device offers an external quantum efficiency of 19.5% and reduced efficiency roll-off characteristics at high luminance. Through computational simulation, we identified six pretwisted intramolecular charge-transfer (CT) molecules with small singlet–triplet CT state splitting but different energy relationships between 3CT and locally excited triplet (3LE) states. Systematic comparison of their excited-state dynamics revealed that CT molecules with a large twist angle can emit efficient and short-lifetime (a few microseconds) TADF when the emission peak energy is high enough and the 3LE state is higher than the 3CT state.

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Figure 1: Molecular structures and TD-DFT results.
Figure 2: Absorption, emission and transient decay spectra.
Figure 3: Structures and performance of the TADF OLEDs.

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Acknowledgements

This work was supported by a Grant-in-Aid from the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) and the International Institute for Carbon Neutral Energy Research (WPI-I2CNER) sponsored by MEXT. The authors thank J.-L. Brédas, M. Kotani and K. Tokumaru for stimulating discussions regarding this work. The authors also thank W. J. Potscavage Jr for assistance with preparation of this manuscript.

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  1. Qisheng Zhang and Bo Li: These authors contributed equally to this work

Authors and Affiliations

  1. Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi-ku, 819-0395, Fukuoka, Japan

    Qisheng Zhang, Bo Li, Shuping Huang, Hiroko Nomura, Hiroyuki Tanaka & Chihaya Adachi

  2. International Institute for Carbon Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku, 819-0395, Fukuoka, Japan

    Chihaya Adachi

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Contributions

Q.Z. designed the molecules. B.L. measured photoluminescence and electroluminescence characteristics. S.H. performed the computational experiments. Q.Z and H.N. synthesized the compounds. H.T. provided experimental support and suggestions. Q.Z. and C.A. wrote the manuscript.

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Correspondence to Chihaya Adachi.

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Zhang, Q., Li, B., Huang, S. et al. Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence. Nature Photon 8, 326–332 (2014). https://doi.org/10.1038/nphoton.2014.12

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