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Title: Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates

Abstract

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 ηout ≥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. Lastly, 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 inmore » OLEDs.« less

Authors:
 [1];  [1];  [2];  [1];  [3];  [4];  [5];  [6]; ORCiD logo [1];  [7]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Physics & Astronomy Dept.
  2. Iowa State Univ., Ames, IA (United States). Electrical and Computer Engineering Dept.
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Electrical and Computer Engineering Dept., and Microelectronics Research Center
  4. Ames Lab. and Iowa State Univ., Ames, IA (United States). Physics & Astronomy Dept.; Iowa State Univ., Ames, IA (United States). Electrical and Computer Engineering Dept., and Microelectronics Research Center
  5. MicroContinuum, Inc., Cambridge, MA (United States)
  6. Trovato Manufacturing, Inc., Victor, NY (United States)
  7. Iowa State Univ., Ames, IA (United States). Electrical and Computer Engineering Dept., and Microelectronics Research Center
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1425476
Alternate Identifier(s):
OSTI ID: 1415661
Report Number(s):
IS-J-9585
Journal ID: ISSN 2195-1071
Grant/Contract Number:  
SC0011337; EE0007621; AC02-07CH11358
Resource Type:
Accepted Manuscript
Journal Name:
Advanced Optical Materials
Additional Journal Information:
Journal Volume: 6; Journal Issue: 4; Journal ID: ISSN 2195-1071
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; organic light-emitting diodes; outcoupling; phosphorescent OLEDs; plastic patterned substrates; solid state lighting

Citation Formats

Hippola, Chamika, Kaudal, Rajiv, Manna, Eeshita, Xiao, Teng, Peer, Akshit, Biswas, Rana, Slafer, Warren Dennis, Trovato, Tom, Shinar, Joseph, and Shinar, Ruth. Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates. United States: N. p., 2018. Web. doi:10.1002/adom.201701244.
Hippola, Chamika, Kaudal, Rajiv, Manna, Eeshita, Xiao, Teng, Peer, Akshit, Biswas, Rana, Slafer, Warren Dennis, Trovato, Tom, Shinar, Joseph, & Shinar, Ruth. Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates. United States. doi:10.1002/adom.201701244.
Hippola, Chamika, Kaudal, Rajiv, Manna, Eeshita, Xiao, Teng, Peer, Akshit, Biswas, Rana, Slafer, Warren Dennis, Trovato, Tom, Shinar, Joseph, and Shinar, Ruth. Mon . "Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates". United States. doi:10.1002/adom.201701244. https://www.osti.gov/servlets/purl/1425476.
@article{osti_1425476,
title = {Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates},
author = {Hippola, Chamika and Kaudal, Rajiv and Manna, Eeshita and Xiao, Teng and Peer, Akshit and Biswas, Rana and Slafer, Warren Dennis and Trovato, Tom and Shinar, Joseph and Shinar, Ruth},
abstractNote = {A key scientific and technological challenge in organic light-emitting diodes (OLEDs) is enhancing the light outcoupling factor ηout, which is typically <20%. This paper reports experimental and modeling results of a promising approach to strongly increase ηout 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 ηout ≥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. Lastly, 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.},
doi = {10.1002/adom.201701244},
journal = {Advanced Optical Materials},
number = 4,
volume = 6,
place = {United States},
year = {2018},
month = {2}
}

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Figures / Tables:

Figure 1 Figure 1: Left: AFM image of a 10x10 μm2 convex PC with $h$ ~320 nm and $a$ ~750 nm; Center: AFM image of a 10x10 μm2 concave PET/CAB with $h$ ~250 nm and $a$ ~1.75 μm coated with ITO. Right: FIB image (with 20 μm scale bar) of ITO onmore » corrugated PET/CAB showing damaged areas.« less

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