Enhancing waveguided light extraction in organic LEDs using an ultra-low-index grid

Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
Optics Letters (Impact Factor: 3.29). 04/2010; 35(7):1052-4. DOI: 10.1364/OL.35.001052
Source: PubMed


Improved outcoupling of light into substrate modes of an organic LED (OLED) by an ultra-low index of refraction (n=1.15), porous SiO(2) grid (UltraLIG) fabricated using glancing-angle deposition is demonstrated. Outcoupling into the substrate for electrophosphorescent tris(2-phenylpyridine) iridium [Ir(ppy)(3)]-based OLEDs grown on substrates with the UltraLIG is increased by 48% over a conventional device at a luminance of 100 cd/m(2). With efficient light outcoupling at the substrate-air interface, the UltraLIG devices attain eta(EQE)=22.5% and eta(P)=64 lm/W at their peak efficiencies, a nearly threefold increase over an analogous conventional OLED.

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    • "OLEDs, such as the micro lens array, two-dimensional periodic nanostructures, nano-scattering medium and the low-index grid approach [14] [15]. Nevertheless, there is still a fundamental restriction to increase h out , so that the importance of enhancing the internal quantum efficiency (h int ) is mostly highlighted. "
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