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Delocalizing electron distribution in thermally activated delayed fluorophors for high-efficiency and long-lifetime blue electroluminescence

Nature Materials volume 23, pages 1523–1530 (2024)Cite this article

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Abstract

Blue thermally activated delayed fluorescent emitters are promising for the next generation of organic light-emitting diodes, yet their performance still cannot meet the requirements for commercialization. Here we establish a design rule for highly efficient and stable thermally activated delayed fluorescent emitters by introducing an auxiliary acceptor that could delocalize electron distributions, enhancing molecular stability in both the negative polaron and triplet excited state, while also accelerating triplet-to-singlet up-conversion and singlet radiative processes simultaneously. Proof-of-concept thermally activated delayed fluorescent compounds, based on a multi-carbazole-benzonitrile structure, exhibit near-unity photoluminescent quantum yields, short-lived delays and improved photoluminescent and electroluminescent stabilities. A deep-blue organic light-emitting diode using one of these molecules as a sensitizer for a multi-resonance emitter achieves a remarkable time to 95% of initial luminance of 221 h at an initial luminance of 1,000 cd m−2, a maximum external quantum efficiency of 30.8% and Commission Internationale de l’Eclairage coordinates of (0.14, 0.17).

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Fig. 1: Molecular design and intrinsic stability analysis of the TADF molecules.
Fig. 2: PL properties of the TADF materials.
Fig. 3: Optimized EL properties of TADF-based OLEDs.
Fig. 4: Optimized EL properties of TSF-based OLEDs.

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Data availability

The authors declare that the data supporting the findings of this study are available within the paper and its Supplementary Information file. The X-ray crystallographic coordinates for structures reported in this study have been deposited at the CCDC under deposition numbers 2232729, 2232730 and 2232731. These data can be obtained free of charge from the CCDC via www.ccdc.cam.ac.uk/data_request/cif. Source data are provided with this paper.

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Acknowledgements

This work is supported by the National Natural Science Foundation of China (grant numbers 52222308 to D.Z. and 22135004 to L.D.), the National Key Research and Development Program (numbers 2022YFB3603002 to T.H. and 2023YFE0203300 to L.D.) and the Guangdong Major Project of Basic and Applied Basic Research (grant number 2019B030302009 to L.D.). We thank J. Qiao and Q. Meng from Tsinghua University for their assistance in calculating BDE values and providing valuable suggestions. We also extend our gratitude to H. Zhong, X. Wu and M. Yang from Beijing Institute of Technology for their support with photoelectrical ageing measurements. Additionally, we thank L. Wang and S. Wang from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, for providing the multi-resonance TADF material t-BuCz-DABNA.

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Authors and Affiliations

  1. Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, China

    Tianyu Huang, Qi Wang, Hai Zhang, Yangyang Xin, Dongdong Zhang & Lian Duan

  2. Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing, China

    Yuewei Zhang & Lian Duan

  3. Institute of Functional Nano & Soft Materials (FUNSOM), Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou, China

    Xiankai Chen

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  1. Tianyu Huang
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Contributions

L.D. and D.Z. conceived and supervised this work. D.Z. proposed the molecular design concept and designed the experiments. T.H. carried out the quantum chemical calculations and did the main work on materials synthesis, device fabrication and both material and device characterization. Q.W. and H.Z. helped with the synthesis of the materials, while Y.X. and Y.Z. helped measure the device performances. X.C. helped revise the paper. L.D., D.Z. and T.H. discussed the results and wrote and revised the paper with input from all authors.

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Correspondence to Dongdong Zhang or Lian Duan.

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Huang, T., Wang, Q., Zhang, H. et al. Delocalizing electron distribution in thermally activated delayed fluorophors for high-efficiency and long-lifetime blue electroluminescence. Nat. Mater. 23, 1523–1530 (2024). https://doi.org/10.1038/s41563-024-02004-w

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