TY - JOUR
T1 - Enhanced outcoupling in flexible organic light-emitting diodes on scattering polyimide substrates
AU - Lee, Kyung Min
AU - Fardel, Romain
AU - Zhao, Lianfeng
AU - Arnold, Craig B.
AU - Rand, Barry P.
N1 - Funding Information:
We acknowledge funding for this work from the DOE EERE SSL Program [Award #DE- EE0006672 ]. B.P.R. acknowledges support from a 3M Nontenured Faculty Award and DARPA Young Faculty Award. R.F. and C.B.A. acknowledge the support of the National Science Foundation via the MRSEC at Princeton [ DMR-0819860 ] and the usage of the PRISM Imaging and Analysis Center.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/12
Y1 - 2017/12
N2 - We demonstrate an upscalable approach to increase outcoupling in organic light-emitting diodes (OLEDs) fabricated on flexible substrates. The outcoupling enhancement is enabled by introducing a thin film of microporous polyimide on the backside of silver nanowire (AgNW) electrodes embedded in neat colorless polyimide. This porous polyimide film, prepared by immersion precipitation, utilizes a large index contrast between the polyimide host and randomly distributed air voids, resulting in broadband haze (>75%). In addition, the composite polyimide/AgNW scattering substrate inherits the high thermal (>360 °C), chemical, and mechanical stability of polyimides. The outcoupling efficiency of the composite scattering substrate is studied via optical characterization of the composite substrate and electron microscopy of the scattering film. The flexible scattering substrates compared to glass/indium tin oxide (ITO) allows for a 74% enhancement in external quantum efficiency (EQE) for a phosphorescent green OLED, and 68% EQE enhancement for a phosphorescent white OLED. The outcoupling enhancement remains unharmed after 5000 bending cycles at a 2 mm bending radius. Moreover, the color uniformity over viewing angles is improved, an important feature for lighting applications.
AB - We demonstrate an upscalable approach to increase outcoupling in organic light-emitting diodes (OLEDs) fabricated on flexible substrates. The outcoupling enhancement is enabled by introducing a thin film of microporous polyimide on the backside of silver nanowire (AgNW) electrodes embedded in neat colorless polyimide. This porous polyimide film, prepared by immersion precipitation, utilizes a large index contrast between the polyimide host and randomly distributed air voids, resulting in broadband haze (>75%). In addition, the composite polyimide/AgNW scattering substrate inherits the high thermal (>360 °C), chemical, and mechanical stability of polyimides. The outcoupling efficiency of the composite scattering substrate is studied via optical characterization of the composite substrate and electron microscopy of the scattering film. The flexible scattering substrates compared to glass/indium tin oxide (ITO) allows for a 74% enhancement in external quantum efficiency (EQE) for a phosphorescent green OLED, and 68% EQE enhancement for a phosphorescent white OLED. The outcoupling enhancement remains unharmed after 5000 bending cycles at a 2 mm bending radius. Moreover, the color uniformity over viewing angles is improved, an important feature for lighting applications.
KW - Colorless polyimide
KW - Flexible organic light-emitting diodes
KW - Outcoupling
KW - Scattering substrate
KW - Silver nanowires
KW - White organic light emitting devices
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U2 - 10.1016/j.orgel.2017.09.042
DO - 10.1016/j.orgel.2017.09.042
M3 - Article
AN - SCOPUS:85030558088
SN - 1566-1199
VL - 51
SP - 471
EP - 476
JO - Organic Electronics: physics, materials, applications
JF - Organic Electronics: physics, materials, applications
ER -