Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Diboron compound-based organic light-emitting diodes with high efficiency and reduced efficiency roll-off

Nature Photonics volume 12, pages 235–240 (2018)Cite this article

Subjects

Abstract

Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) materials are promising for the realization of highly efficient light emitters. However, such devices have so far suffered from efficiency roll-off at high luminance. Here, we report the design and synthesis of two diboron-based molecules, CzDBA and tBuCzDBA, which show excellent TADF properties and yield efficient OLEDs with very low efficiency roll-off. These donor–acceptor–donor (D–A–D) type and rod-like compounds concurrently generate TADF with a photoluminescence quantum yield of ~100% and an 84% horizontal dipole ratio in the thin film. A green OLED based on CzDBA exhibits a high external quantum efficiency of 37.8 ± 0.6%, a current efficiency of 139.6 ± 2.8 cd A−1 and a power efficiency of 121.6 ± 3.1 lm W−1 with an efficiency roll-off of only 0.3% at 1,000 cd m−2. The device has a peak emission wavelength of 528 nm and colour coordinates of the Commission International de l´Eclairage (CIE) of (0.31, 0.61), making it attractive for colour-display applications.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Synthetic route and theoretical results of DBA compounds.
Fig. 2: Photophysical properties of the DBA derivatives.
Fig. 3: Performance of optimized diboron-based OLEDs and measurement of molecular orientation.

Similar content being viewed by others

References

  1. Smith, L. H., Wasey, J. A. E. & Barnes, W. L. Light outcoupling efficiency of top-emitting organic light-emitting diodes. Appl. Phys. Lett. 84, 2986–2988 (2004).

    Article  ADS  Google Scholar 

  2. Kuei, C. Y. et al. Bis-tridentate Ir(III) complexes with nearly unitary RGB phosphorescence and organic light-emitting diodes with external quantum efficiency exceeding 31%. Adv. Mater. 28, 2795–2800 (2016).

  3. Uoyama, H., Goushi, K., Shizu, K., Nomura, H. & Adachi, C. Highly efficient organic light-emitting diodes from delayed fluorescence. Nature 492, 234–238 (2012).

    Article  ADS  Google Scholar 

  4. Jankus, V., Chiang, C. J., Dias, F. & Monkman, A. P. Deep blue exciplex organic light-emitting diodes with enhanced efficiency; p-type or e-type triplet conversion to singlet excitons? Adv. Mater. 25, 1455–1459 (2013).

    Article  Google Scholar 

  5. Murawski, C., Leo, K. & Gather, M. C. Efficiency roll-off in organic light-emitting diodes. Adv. Mater. 25, 6801–6827 (2013).

    Article  Google Scholar 

  6. Masui, K., Nakanotani, H. & Adachi, C. Analysis of exciton annihilation in high-efficiency sky-blue organic light-emitting diodes with thermally activated delayed fluorescence. Org. Electron. 14, 2721–2726 (2013).

    Article  Google Scholar 

  7. Cai, X. Y. et al. “Rate-limited effect” of reverse intersystem crossing process: the key for tuning thermally activated delayed fluorescence lifetime and efficiency roll-off of organic light emitting diodes. Chem. Sci. 7, 4264–4275 (2016).

  8. Zhang, D. D. et al. Highly efficient full-color thermally activated delayed fluorescent organic light-emitting diodes: extremely low efficiency roll-off utilizing a host with small singlet-triplet splitting. ACS Appl. Mater. Interf. 9, 4769–4777 (2017).

    Article  Google Scholar 

  9. Zhang, Q. S. et al. Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence. Nat. Photon. 8, 326–332 (2014).

    Article  ADS  Google Scholar 

  10. Wang, S. et al. Achieving high power efficiency and low roll-off OLEDs based on energy transfer from thermally activated delayed excitons to fluorescent dopants. Chem. Commun. 51, 11972–11975 (2015).

  11. Zhang, Q. S. et al. Anthraquinone-based intramolecular charge-transfer compounds: computational molecular design, thermally activated delayed fluorescence, and highly efficient red electroluminescence. J. Am. Chem. Soc. 136, 18070–18081 (2014).

    Article  Google Scholar 

  12. Data, P. et al. Dibenzo[a,j]phenazine-cored donor-acceptor-donor compounds as green-to-red/NIR thermally activated delayed fluorescence organic light emitters. Angew. Chem. Int. Ed. 55, 5739–5744 (2016).

  13. Goushi, K., Yoshida, K., Sato, K. & Adachi, C. Organic light-emitting diodes employing efficient reverse intersystem crossing for triplet-to-singlet state conversion. Nat. Photon. 6, 253–258 (2012).

    Article  ADS  Google Scholar 

  14. Tao, Y. et al. Thermally activated delayed fluorescence materials towards the breakthrough of organoelectronics. Adv. Mater. 26, 7931–7958 (2014).

    Article  Google Scholar 

  15. Endo, A. et al. Thermally activated delayed fluorescence from Sn4+-porphyrin complexes and their application to organic light emitting diodes–a novel mechanism for electroluminescence. Adv. Mater. 21, 4802–4806 (2009).

  16. Deaton, J. C. et al. E-type delayed fluorescence of a phosphine-supported Cu2(μ-NAr2)2 diamond core: harvesting singlet and triplet excitons in OLEDs. J. Am. Chem. Soc. 132, 9499–9508 (2010).

    Article  Google Scholar 

  17. Hirata, S. et al. Highly efficient blue electroluminescence based on thermally activated delayed fluorescence. Nat. Mater. 14, 330–336 (2015).

    Article  ADS  Google Scholar 

  18. Wong, M. Y. & Zysman-Colman, E. Purely organic thermally activated delayed fluorescence materials for organic light-emitting diodes. Adv. Mater. 29, 1605444 (2017).

    Article  Google Scholar 

  19. Kim, S.-Y. et al. Organic light-emitting diodes with 30% external quantum efficiency based on a horizontally oriented emitter. Adv. Funct. Mater. 23, 3896–3900 (2013).

    Article  Google Scholar 

  20. Lin, T. A. et al. Sky-blue organic light emitting diode with 37% external quantum efficiency using thermally activated delayed fluorescence from spiroacridine-triazine hybrid. Adv. Mater. 28, 6976–6983 (2016).

    Article  ADS  Google Scholar 

  21. Rajamalli, P. et al. New molecular design concurrently providing superior pure blue, thermally activated delayed fluorescence and optical out-coupling efficiencies. J. Am. Chem. Soc. 139, 10948–10951 (2017).

    Article  Google Scholar 

  22. Pan, K. C. et al. Efficient and tunable thermally activated delayed fluorescence emitters having orientation-adjustable CN-substituted pyridine and pyrimidine acceptor units. Adv. Funct. Mater. 26, 7560–7571 (2016).

    Article  Google Scholar 

  23. Ly, K. T. et al. Near-infrared organic light-emitting diodes with very high external quantum efficiency and radiance. Nat. Photon. 11, 63–68 (2017).

    Article  ADS  Google Scholar 

  24. Yokoyama, D. Molecular orientation in small-molecule organic light-emitting diodes. J. Mater. Chem. 21, 19187–19202 (2011).

    Article  Google Scholar 

  25. Lin, H. W. et al. Anisotropic optical properties and molecular orientation in vacuum-deposited ter(9,9-diarylfluorene)s thin films using spectroscopic ellipsometry. J. Appl. Phys. 95, 881–886 (2004).

    Article  ADS  Google Scholar 

  26. Kim, K. H., Ahn, E. S., Huh, J. S., Kim, Y. H. & Kim, J. J. Design of heteroleptic Ir complexes with horizontal emitting dipoles for highly efficient organic light-emitting diodes with an external quantum efficiency of 38%. Chem. Mater. 28, 7505–7510 (2016).

    Article  Google Scholar 

  27. Hirai, H. et al. One-step borylation of 1,3-diaryloxybenzenes towards efficient materials for organic light-emitting diodes. Angew. Chem. Int. Ed. 54, 13581–13585 (2015).

    Article  Google Scholar 

  28. Suzuki, K. et al. Triarylboron-based fluorescent organic light-emitting diodes with external quantum efficiencies exceeding 20%. Angew. Chem. Int. Ed. 54, 15231–15235 (2015).

  29. Hatakeyama, T. et al. Ultrapure blue thermally activated delayed fluorescence molecules: efficient HOMO-LUMO separation by the multiple resonance effect. Adv. Mater. 28, 2777–2781 (2016).

    Article  Google Scholar 

  30. Numata, M., Yasuda, T. & Adachi, C. High efficiency pure blue thermally activated delayed fluorescence molecules having 10H-phenoxaborin and acridan units. Chem. Commun. 51, 9443–9446 (2015).

    Article  Google Scholar 

  31. Ji, L., Griesbeck, S. & Marder, T. B. Recent developments in and perspectives on three-coordinate boron materials: a bright future. Chem. Sci. 8, 846–863 (2017).

    Article  Google Scholar 

  32. Escande, A. & Ingleson, M. J. Fused polycyclic aromatics incorporating boron in the core: fundamentals and applications. Chem. Commun. 51, 6257–6274 (2015).

    Article  Google Scholar 

  33. Kawai, S. et al. Atomically controlled substitutional boron-doping of graphene nanoribbons. Nat. Commun. 6, 8098 (2015).

    Article  Google Scholar 

  34. Wu, T.-L. et al. High-performance organic light-emitting diode with substitutionally boron-doped graphene anode. ACS Appl. Mater. Interfaces 9, 14998–15004 (2017).

    Article  Google Scholar 

  35. Yang, Z. Y. et al. Recent advances in organic thermally activated delayed fluorescence materials. Chem. Soc. Rev. 46, 915–1016 (2017).

    Article  Google Scholar 

  36. Reus, C., Weidlich, S., Bolte, M., Lerner, H. W. & Wagner, M. C-functionalized, air- and water-stable 9,10-dihydro-9,10-diboraanthracenes: efficient blue to red emitting luminophores. J. Am. Chem. Soc. 135, 12892–12907 (2013).

    Article  Google Scholar 

  37. Zhang, Q. S. et al. Triplet exciton confinement in green organic light-emitting diodes containing luminescent charge-transfer Cu(I) complexes. Adv. Funct. Mater. 22, 2327–2336 (2012).

    Article  Google Scholar 

  38. Mei, J. et al. Aggregation-induced emission: the whole is more brilliant than the parts. Adv. Mater. 26, 5429–5479 (2014).

    Article  Google Scholar 

  39. Rajamalli, P. et al. A new molecular design based on thermally activated delayed fluorescence for highly efficient organic light emitting diodes. J. Am. Chem. Soc. 138, 628–634 (2016).

    Article  Google Scholar 

  40. Xiang, C. Y. et al. Efficiency roll-off in blue emitting phosphorescent organic light emitting diodes with carbazole host materials. Adv. Funct. Mater. 26, 1463–1469 (2016).

    Article  Google Scholar 

  41. Lin, C.-C. et al. Molecular design of highly efficient thermally activated delayed fluorescence hosts for blue phosphorescent and fluorescent organic light-emitting diodes. Chem. Mater. 29, 1527–1537 (2017).

    Article  Google Scholar 

  42. Guo, J. et al. Achieving high-performance nondoped OLEDs with extremely small efficiency roll-off by combining aggregation-induced emission and thermally activated delayed fluorescence. Adv. Funct. Mater. 27, 1606458 (2017).

  43. Laudise, R. A., Kloc, C., Simpkins, P. G. & Siegrist, T. Physical vapor growth of organic semiconductors. J. Cryst. Growth 187, 449–454 (1998).

    Article  ADS  Google Scholar 

  44. Januszewski, E. et al. Unsymmetrically substituted 9,10-dihydro-9,10-diboraanthracenes as versatile building blocks for boron-doped π-conjugated systems. Chem. Eur. J. 17, 12696–12705 (2011).

    Article  Google Scholar 

Download references

Acknowledgements

The authors gratefully acknowledge the financial support of the Ministry of Science and Technology (MOST 105-2633-M-007-003; MOST 106-2119-M-007-020; MOST 106-2745-M-007-001) and the Ministry of Education, Taiwan, and also thank the National Center for High-Performance Computing (Account number: u32chc04) of Taiwan for providing the computing time.

Author information

Authors and Affiliations

  1. Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan

    Tien-Lin Wu, Min-Jie Huang, Chih-Chun Lin, Pei-Yun Huang, Rai-Shung Liu & Chien-Hong Cheng

  2. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

    Tsu-Yu Chou, Ren-Wu Chen-Cheng & Hao-Wu Lin

Authors
  1. Tien-Lin Wu
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Min-Jie Huang
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Chih-Chun Lin
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Pei-Yun Huang
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Tsu-Yu Chou
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Ren-Wu Chen-Cheng
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Hao-Wu Lin
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Rai-Shung Liu
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Chien-Hong Cheng
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

T.-L.W. and C.-H.C. contributed to the manuscript writing. T.-L.W. designed, synthesized and characterized the organoboron molecules, then measured and analysed their chemical and photophysical properties. M.-J.H. developed the theoretical calculation and performed the computational experiments. C.-C.L. designed the optimized OLED configuration, P.-Y.H. fabricated all of the OLED devices, measured the electroluminescence and prepared thin films. T.-Y.C. conducted the transient PL and low-temperature measurements, R.-W.C.-C. determined molecular emitting dipole orientations. H.-W.L. provided experimental methods and analysed the optical data. R.-S.L. and C.-H.C. provided the synthetic supports and suggestions. All authors discussed the progress of research and reviewed the manuscript.

Corresponding authors

Correspondence to Hao-Wu Lin, Rai-Shung Liu or Chien-Hong Cheng.

Ethics declarations

Competing interests

NTHU has filed patent applications on materials and devices.

Additional information

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary chemical data, fabrication procedures, characterization and properties.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Wu, TL., Huang, MJ., Lin, CC. et al. Diboron compound-based organic light-emitting diodes with high efficiency and reduced efficiency roll-off. Nature Photon 12, 235–240 (2018). https://doi.org/10.1038/s41566-018-0112-9

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41566-018-0112-9

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing