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.

Highly efficient organic light-emitting diodes from delayed fluorescence

Nature volume 492, pages 234–238 (2012)Cite this article

Subjects

Abstract

The inherent flexibility afforded by molecular design has accelerated the development of a wide variety of organic semiconductors over the past two decades. In particular, great advances have been made in the development of materials for organic light-emitting diodes (OLEDs), from early devices based on fluorescent molecules1 to those using phosphorescent molecules2,3. In OLEDs, electrically injected charge carriers recombine to form singlet and triplet excitons in a 1:3 ratio1; the use of phosphorescent metal–organic complexes exploits the normally non-radiative triplet excitons and so enhances the overall electroluminescence efficiency2,3. Here we report a class of metal-free organic electroluminescent molecules in which the energy gap between the singlet and triplet excited states is minimized by design4, thereby promoting highly efficient spin up-conversion from non-radiative triplet states to radiative singlet states while maintaining high radiative decay rates, of more than 106 decays per second. In other words, these molecules harness both singlet and triplet excitons for light emission through fluorescence decay channels, leading to an intrinsic fluorescence efficiency in excess of 90 per cent and a very high external electroluminescence efficiency, of more than 19 per cent, which is comparable to that achieved in high-efficiency phosphorescence-based OLEDs3.

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

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

Buy

All prices are NET prices.

Figure 1: Energy diagram and molecular structures of CDCBs.
Figure 2: Photoluminescence characteristics of 4CzIPN.
Figure 3: Photoluminescence of the CDCB series.
Figure 4: Temperature dependence of photoluminescence characteristics of a 5 ± 1 wt% 4CzIPN:CBP film.
Figure 5: Performance of OLEDs containing CDCB derivatives.

References

  1. Pope, M., Kallmann, H. P. & Magnante, P. Electroluminescence in organic crystals. J. Chem. Phys. 38, 2042–2043 (1963)

    Article  ADS  CAS  Google Scholar 

  2. Baldo, M. A., Lamansky, S., Burrows, P. E., Thompson, M. E. & Forrest, S. R. Very high-efficiency green organic light-emitting devices based on electrophosphorescence. Appl. Phys. Lett. 75, 4–6 (1999)

    Article  ADS  CAS  Google Scholar 

  3. Adachi, C., Baldo, M. A., Thompson, M. E. & Forrest, S. R. Nearly 100% internal phosphorescence efficiency in an organic light emitting device. J. Appl. Phys. 90, 5048–5051 (2001)

    Article  ADS  CAS  Google Scholar 

  4. Endo, A. et al. Efficient up-conversion of triplet excitons into a singlet state and its application to organic light emitting diodes. Appl. Phys. Lett. 98, 083302 (2011)

    Article  ADS  Google Scholar 

  5. Bernanose, A., Comte, M. & Vouaux, P. A new method of emission of light by certain organic compounds. J. Chim. Phys. 50, 64–68 (1953)

    Article  CAS  Google Scholar 

  6. Tsutsui, T. & Saito, S. Organic Multilayer-Dye Electroluminescent Diodes: Is There Any Difference with Polymer LED? 127–131 (Kluwer, 1993)

    Google Scholar 

  7. Rothberg, L. J. & Lovinger, A. J. Status of and prospects for organic electroluminescence. J. Mater. Res. 11, 3174–3187 (1996)

    Article  ADS  CAS  Google Scholar 

  8. Wilson, J. S. et al. Spin-dependent exciton formation in π-conjugated compounds. Nature 413, 828–831 (2001)

    Article  ADS  CAS  Google Scholar 

  9. Segal, M., Baldo, M. A., Holmes, R. J., Forrest, S. R. & Soos, Z. G. Excitonic singlet-triplet ratios in molecular and polymeric organic materials. Phys. Rev. B 68, 075211 (2003)

    Article  ADS  Google Scholar 

  10. Cao, Y., Parker, I. D., Yu, G., Zhang, C. & Heeger, A. J. Improved quantum efficiency for electroluminescence in semiconducting polymers. Nature 397, 414–417 (1999)

    Article  ADS  CAS  Google Scholar 

  11. Wohlgenannt, M., Jiang, X. M., Vardeny, Z. V. & Janssen, R. A. J. Conjugation-length dependence of spin-dependant exciton formation rates in p-conjugated oligomers and polymers. Phys. Rev. Lett. 88, 197401 (2002)

    Article  ADS  CAS  Google Scholar 

  12. Shuai, Z., Beljonne, D., Silbey, R. J. & Brédas, L. J. Singlet and triplet exciton formation rates in conjugated polymer light-emitting diodes. Phys. Rev. Lett. 84, 131–134 (2000)

    Article  ADS  CAS  Google Scholar 

  13. Tsutsui, T., Adachi, C. & Saito, S. in Photochemical Processes in Organized Molecular Systems (ed. Honda, K.) 437–450 (Elsevier, 1991)

  14. Kido, J., Nagai, K. & Ohashi, Y. Electroluminescence in a terbium complex. Chem. Lett. 19, 657–660 (1990)

    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)

    Article  CAS  Google Scholar 

  16. Akai, N., Kudoh, S. & Nakata, M. Lowest excited triplet states of 1,2- and 1,4-dicyanobenzenes by low-temperature matrix-isolation infrared spectroscopy and density-functional-theory calculation. Chem. Phys. Lett. 371, 655–661 (2003)

    Article  ADS  CAS  Google Scholar 

  17. Wakamiya, A., Mori, K. & Yamaguchi, S. 3-boryl-2,2′-bithiophene as a versatile core skeleton for full-color highly emissive organic solids. Angew. Chem. Int. Ed. 46, 4273–4276 (2007)

    Article  CAS  Google Scholar 

  18. Hariharan, P. C. & Pople, J. A. The influence of polarization functions on molecular orbital hydrogenation energies. Theor. Chim. Acta 28, 213–222 (1973)

    Article  CAS  Google Scholar 

  19. Frisch, M. J. et al. Gaussian 09, Revision C. 01http://www.gaussian.com/index.htm (2010)

  20. Zhao, Y. & Truhlar, D. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theor. Chem. Acc. 120, 215–241 (2008)

    Article  CAS  Google Scholar 

  21. Improta, R., Barone, V., Scalmani, G. & Frisch, M. J. A state-specific polarizable continuum model time dependent density functional method for excited state calculations in solution. J. Chem. Phys. 125, 054103 (2006)

    Article  ADS  Google Scholar 

  22. Improta, R., Scalmani, G., Frisch, M. J. & Barone, V. Toward effective and reliable fluorescence energies in solution by a new state specific polarizable continuum model time dependent density functional theory approach. J. Chem. Phys. 127, 074504 (2007)

    Article  ADS  Google Scholar 

  23. Martin, R. L. Natural transition orbitals. J. Chem. Phys. 118, 4775–4777 (2003)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  25. 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  CAS  Google Scholar 

  26. Tanaka, D. et al. Ultra high efficiency green organic light-emitting devices. Jpn. J. Appl. Phys. 46, L10–L12 (2007)

    Article  CAS  Google Scholar 

  27. Turro, N. J. Modern Molecular Photochemistry 98–100 (Benjamin Cummings, 1978)

    Google Scholar 

  28. Beljonne, D., Shuai, Z., Pourtois, G. & Brédas, J. L. Spin-orbit coupling and intersystem crossing in conjugated polymers: a configuration interaction description. J. Phys. Chem. A 105, 3899–3907 (2001)

    Article  CAS  Google Scholar 

  29. Takase, M., Enkelmann, V., Sebastiani, D., Baumgarten, M. & Müllen, K. Annularly fused hexapyrrolohexaazacoronenes: an extended π system with multiple interior nitrogen atoms displays stable oxidation states. Angew. Chem. Int. Ed. 46, 5524–5527 (2007)

    Article  CAS  Google Scholar 

  30. Uno, H. et al. Preparation of highly conjugated oligoaza-PAHs based on the oxidative intramolecular coupling of bicyclo[2.2.2]octadiene-fused pyrrole. Heterocycles 82, 791–802 (2010)

    Article  CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by 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 the Japanese Ministry of Education, Culture, Sports, Science and Technology. H.U. acknowledges a Grand-in-Aid for JSPS Fellows. We thank H. Nakanotani, J.-i. Nishide, and H. Miyazaki for their assistance with this research. We also thank K. Tokumaru, H. Sasabe, W. Potscavage and M. Gábor for their assistance with preparation of this manuscript.

Author information

Authors and Affiliations

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

    Hiroki Uoyama, Kenichi Goushi, Katsuyuki Shizu, Hiroko Nomura & Chihaya Adachi

  2. International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan,

    Kenichi Goushi & Chihaya Adachi

Authors
  1. Hiroki Uoyama
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Kenichi Goushi
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Katsuyuki Shizu
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Hiroko Nomura
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Chihaya Adachi
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

H.U. performed the molecular design. H.U. and H.N. performed the synthetic work. K.S. performed the computational experiments. H.U. and K.G. measured the photoluminescence and electroluminescence characteristics of the compounds. All authors wrote the paper. C.A. thought of the TADF concept and supervised the project.

Corresponding author

Correspondence to Chihaya Adachi.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-2 and Supplementary Tables 1-4. (PDF 266 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Uoyama, H., Goushi, K., Shizu, K. et al. Highly efficient organic light-emitting diodes from delayed fluorescence. Nature 492, 234–238 (2012). https://doi.org/10.1038/nature11687

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature11687

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

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