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Tailor-made nanostructures bridging chaosand order for highly efficient white organiclight-emitting diodes

 
: Li, Yungui; Kovačič, Milan; Westphalen, Jasper; Oswald, Steffen; Hänisch, Christian; Will, Paul-Anton; Jiang, Lihui; Junghähnel, Manuela; Scholz, Reinhard; Lenk, Simone; Reinecke, Sebastian

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Fulltext ()

Nature Communications 10 (2019), Art. 2972, 11 pp.
ISSN: 2041-1723
European Commission EC
H2020; 679213; BILUM
English
Journal Article, Electronic Publication
Fraunhofer FEP ()
OLED; Nanostructures; organic light emitting diode

Abstract
Organic light-emitting diodes (OLEDs) suffer from notorious light trapping, resulting in onlymoderate external quantum efficiencies. Here, we report a facile, scalable, lithography-freemethod to generate controllable nanostructures with directional randomness and dimensionalorder, significantly boosting the efficiency of white OLEDs. Mechanical deformationsform on the surface of poly(dimethylsiloxane) in response to compressive stress release,initialized by reactive ions etching with periodicity and depth distribution ranging from dozensof nanometers to micrometers. We demonstrate the possibility of independently tuning theaverage depth and the dominant periodicity. Integrating these nanostructures into a two-unittandem white organic light-emitting diode, a maximum external quantum efficiency of 76.3%and a luminous efficacy of 95.7 lmW−1 are achieved with extracted substrate modes. Theenhancement factor of 1.53 ± 0.12 at 10,000 cdm−2 is obtained. An optical model is built byconsidering the dipole orientation, emitting wavelength, and the dipole position on thesinusoidal nanotexture.

: http://publica.fraunhofer.de/documents/N-551996.html