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Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates
Author(s) -
Hippola Chamika,
Kaudal Rajiv,
Manna Eeshita,
Xiao Teng,
Peer Akshit,
Biswas Rana,
Slafer Warren Dennis,
Trovato Tom,
Shinar Joseph,
Shinar Ruth
Publication year - 2018
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201701244
Subject(s) - oled , materials science , pedot:pss , optoelectronics , substrate (aquarium) , anode , quantum efficiency , polystyrene , cathode , diode , layer (electronics) , nanotechnology , polymer , composite material , electrode , oceanography , chemistry , geology
A key scientific and technological challenge in organic light‐emitting diodes (OLEDs) is enhancing the light outcoupling factor η out , which is typically <20%. This paper reports experimental and modeling results of a promising approach to strongly increase η out by fabricating OLEDs on novel flexible nanopatterned substrates that result in a >2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning η out ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed for blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost‐effectively by direct room‐temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome‐shaped convex nanopatterns with height of ∼280–400 nm and pitch ∼750–800 nm were found to be optimal. Substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs.