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.

  • Letter
  • Published:

Unlocking the full potential of organic light-emitting diodes on flexible plastic

Nature Photonics volume 5, pages 753–757 (2011)Cite this article

Subjects

Abstract

Typical high-efficiency organic light-emitting diodes (OLEDs) require exotic high-refractive-index (n ≥ 1.8) substrates to enhance the outcoupling of trapped light in the device. One of the exciting possibilities of OLEDs is the use of lightweight flexible plastic substrates, which unfortunately have a low refractive index (n ≤ 1.6). To unlock the full potential of OLEDs on flexible plastic, we report high-efficiency phosphorescent OLEDs using a thin-film outcoupling enhancement method that does not depend on high-index substrates. In these devices, multifunctional anode stacks, consisting of a high-index Ta2O5 optical coupling layer, electrically conductive gold layer and hole-injection MoO3 layer, are collectively optimized to achieve high efficiency. The maximum external quantum efficiency reaches 63% for green, which remains as high as 60% at >10,000 cd m–2.

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

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

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

Figure 1: Device structure of the flexible OLED.
Figure 2: Calculation of optical enhancement ratio.
Figure 3: Comparison of calculated and measured luminance and electroluminescence spectra.
Figure 4: Device performance of optimized OLEDs.

Similar content being viewed by others

References

  1. Sun, Y. et al. Management of singlet and triplet excitons for efficient white organic light-emitting devices. Nature 440, 908–912 (2006).

    Article  ADS  Google Scholar 

  2. Segal, M. et al. Extrafluorescent electroluminescence in organic light-emitting devices. Nature Mater. 6, 374–378 (2007).

    Article  ADS  Google Scholar 

  3. Sun, Y. & Forrest, S. R. Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids. Nature Photon. 2, 483–487 (2008).

    Article  Google Scholar 

  4. Reineke, S. et al. White organic light-emitting diodes with fluorescent tube efficiency. Nature 459, 234–238 (2009).

    Article  ADS  Google Scholar 

  5. Koo, W. H. et al. Light extraction from organic light-emitting diodes enhanced by spontaneously formed buckles. Nature Photon. 4, 222–226 (2010).

    Article  ADS  Google Scholar 

  6. Capelli, R. et al. Organic light-emitting transistors with an efficiency that outperforms the equivalent light-emitting diodes. Nature Mater. 9, 496–503 (2010).

    Article  ADS  Google Scholar 

  7. van Mensfoort, S. L. M. et al. Measuring the light emission profile in organic light-emitting diodes with nanometre spatial resolution. Nature Photon. 4, 329–335 (2010).

    Article  Google Scholar 

  8. Sekitani, T. et al. Stretchable active-matrix organic light-emitting diode display using printable elastic conductors. Nature Mater. 8, 494–499 (2009).

    Article  ADS  Google Scholar 

  9. Mikami, A. & Koyanagi, T. 60.4L: Late News Paper: high efficiency 200-lm/W green light emitting organic devices prepared on high-index of refraction substrate. SID Symposium Digest of Technical Papers 40, 907–910 (2009).

    Article  Google Scholar 

  10. Mladenovski, S., Neyts, K., Pavicic, D., Werner, A. & Rothe, C. Exceptionally efficient organic light emitting devices using high refractive index substrates. Opt. Express 17, 7562–7570 (2009).

    Article  ADS  Google Scholar 

  11. Forrest, S. R. The path to ubiquitous and low-cost organic electronic appliances on plastic. Nature 428, 911–918 (2004).

    Article  ADS  Google Scholar 

  12. Baldo, M. A. et al. Highly efficient phosphorescent emission from organic electroluminescent devices. Nature 395, 151–154 (1998).

    Article  ADS  Google Scholar 

  13. 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  Google Scholar 

  14. Kawamura, Y. et al. 100% phosphorescence quantum efficiency of Ir(III) complexes in organic semiconductor films. Appl. Phys. Lett. 86, 071104 (2005).

    Article  ADS  Google Scholar 

  15. Watanabe, S., Ide, N. & Kido, J. High-efficiency green phosphorescent organic light-emitting devices with chemically doped layers. Jpn J. Appl. Phys. 46, 1186–1188 (2007).

    Article  ADS  Google Scholar 

  16. Reineke, S., Rosenow, T. C., Lüssem, B. & Leo, K. Improved high-brightness efficiency of phosphorescent organic LEDs comprising emitter molecules with small permanent dipole moments. Adv. Mater. 22, 3189–3193 (2010).

    Article  Google Scholar 

  17. Helander, M. G. et al. Chlorinated indium tin oxide electrodes with high work function for organic device compatibility. Science 332, 944–947 (2011).

    Article  ADS  Google Scholar 

  18. Thomschke, M., Nitsche, R., Furno, M. & Leo, K. Optimized efficiency and angular emission characteristics of white top-emitting organic electroluminescent diodes. Appl. Phys. Lett. 94, 083303 (2009).

    Article  ADS  Google Scholar 

  19. Dodabalapur, A. et al. Physics and applications of organic microcavity light emitting diodes. J. Appl. Phys. 80, 6954–6964 (1996).

    Article  ADS  Google Scholar 

  20. Helander, M. G. et al. Oxidized gold thin films: an effective material for high-performance flexible organic optoelectronics. Adv. Mater. 22, 2037–2040 (2010).

    Article  Google Scholar 

  21. Ishii, H., Sugiyama, K., Ito, E. & Seki, K. Energy level alignment and interfacial electronic structures at organic/metal and organic/organic interfaces. Adv. Mater. 11, 605–625 (1999).

    Article  Google Scholar 

  22. Han, S., Yuan, Y. & Lu, Z. H. Highly efficient organic light-emitting diodes with metal/fullerene anode. J. Appl. Phys. 100, 074504 (2006).

    Article  ADS  Google Scholar 

  23. Wang, Z. B. et al. Highly simplified phosphorescent organic light emitting diode with >20% external quantum efficiency at >10,000 cd/m2. Appl. Phys. Lett. 98, 073310 (2011).

    Article  ADS  Google Scholar 

  24. Wang, Z. B. et al. Direct hole injection in to 4,4′-N,N′-dicarbazole-biphenyl: a simple pathway to achieve efficient organic light emitting diodes. J. Appl. Phys. 108, 024510 (2010).

    Article  ADS  Google Scholar 

  25. Benisty, H., Stanley, R. & Mayer, M. Method of source terms for dipole emission modification in modes of arbitrary planar structures. J. Opt. Soc. Am. A 15, 1192–1201 (1998).

    Article  ADS  Google Scholar 

  26. Helander, M. G., Wang, Z. B., Greiner, M. T., Qiu, J. & Lu, Z. H. Substrate dependent charge injection at the V2O5/organic interface. Appl. Phys. Lett. 95, 083301 (2009).

    Article  ADS  Google Scholar 

  27. Helander, M. G., Wang, Z. B., Qiu, J. & Lu, Z. H. Band alignment at metal/organic and metal/oxide/organic interfaces. Appl. Phys. Lett. 93, 193310 (2008).

    Article  ADS  Google Scholar 

  28. Moller, S. & Forrest, S. R. Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays. J. Appl. Phys. 91, 3324–3327 (2002).

    Article  ADS  Google Scholar 

  29. Tanaka, I. & Tokito, S. Precise measurement of external quantum efficiency of organic light-emitting devices. Jpn J. Appl. Phys. 43, 7733–7736 (2004).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

The authors acknowledge funding for this research from the Natural Sciences and Engineering Research Council (NSERC) of Canada. Z.H.L. is a Government of Canada Research Chair in Organic Optoelectronics, Tier I. The authors are grateful to W.Q. Shi and G.C. Walker (University of Toronto) for atomic force microscopy measurements.

Author information

Author notes

  1. Z. B. Wang and M. G. Helander: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, M5S 3E4, Ontario, Canada

    Z. B. Wang, M. G. Helander, J. Qiu, D. P. Puzzo, M. T. Greiner, Z. W. Liu & Z. H. Lu

  2. Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, K7L 3N6, Ontario, Canada

    Z. M. Hudson & S. Wang

  3. Department of Physics, Yunnan University, 2 Cuihu Beilu, Yunnan, 650091, Kunming, People's Republic of China

    Z. H. Lu

Authors
  1. Z. B. Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. M. G. Helander
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. J. Qiu
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. D. P. Puzzo
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. M. T. Greiner
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Z. M. Hudson
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. S. Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Z. W. Liu
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Z. H. Lu
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

Z.B.W. and M.G.H. designed the device concept, performed the optical simulations, fabricated and characterized the devices and wrote the manuscript. J.Q., D.P.P., M.T.G., Z.M.H., S.W., Z.W.L. and Z.H.L. assisted in characterization and data analysis. Z.H.L. motivated this work and co-wrote the manuscript.

Corresponding authors

Correspondence to Z. B. Wang, M. G. Helander or Z. H. Lu.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 1397 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Wang, Z., Helander, M., Qiu, J. et al. Unlocking the full potential of organic light-emitting diodes on flexible plastic. Nature Photon 5, 753–757 (2011). https://doi.org/10.1038/nphoton.2011.259

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nphoton.2011.259

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