Enhanced light extraction from organic light-emitting devices using a sub-anode grid

Abstract

We demonstrate the highly effective extraction of waveguided light from the active region of organic light-emitting devices using a non-diffractive dielectric grid layer placed between the transparent anode and the substrate. The sub-anode grid couples out all waveguide mode power into the substrate without changing the device electrical properties, resulting in an increase in both the external quantum efficiency and luminous efficacy for green phosphorescent organic light-emitting devices from 15 ± 1% and 36 ± 2 lm W–1 to 18 ± 1% and 43 ± 2 lm W–1. These characteristics are further increased to 40 ± 2% and 95 ± 4 lm W–1 when all glass modes are also extracted. The use of a thick electron transport layer further reduces surface plasmon modes, resulting in an increase in the substrate and air modes by 50 ± 8% compared with devices lacking the grids. The sub-anode grid has minimal impact on organic light-emitting device emission wavelength and viewing angle, and is likely to prove beneficial for a broad range of display and lighting applications.

Figure 1: Sub-anode grid design concept.
Figure 2: Substrate and air mode quantum efficiency (ηSA) enhancement dependence on host and grid materials.
Figure 3: Simulated and measured dependence of outcoupling enhancements on sub-anode grid geometry parameters.
Figure 4: Fraction of power coupled into various PHOLED optical modes as functions of ETL thickness.
Figure 5: Sub-anode grid fabrication process.
Figure 6: Characteristics of conventional and sub-anode grid PHOLEDs.

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Acknowledgements

The authors thank K. Lee for discussions. The authors acknowledge financial support from Universal Display Corporation. This work was performed in part at the Lurie Nanofabrication Facility, a member of the National Nanotechnology Infrastructure Network, which is supported in part by the National Science Foundation.

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Y.Q. performed simulations, fabrication of the PHOLEDs, measurements and data analysis. M.S. designed the sub-anode grid and performed simulations, fabrication and AFM image scans. S.R.F directed the research project and analysed results. All authors discussed the results and contributed to the manuscript.

Corresponding author

Correspondence to Stephen R. Forrest.

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Competing interests

One of the authors (S.R.F.) has a small equity interest in one of the sponsors of this research (Universal Display Corporation).

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Qu, Y., Slootsky, M. & Forrest, S. Enhanced light extraction from organic light-emitting devices using a sub-anode grid. Nature Photon 9, 758–763 (2015). https://doi.org/10.1038/nphoton.2015.194

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