Efficiency of solution-processed multilayer polymer light-emitting diodes using charge blocking layers

By blending semiconducting polymers with the cross-linkable matrix ethoxylated-(4)-bisphenol-a-dimethacrylate (SR540), an insoluble layer is acquired after UV-illumination. Following this approach, a trilayer polymer light-emitting diode (PLED) consisting of a blend of poly[N,N′-bis(4-butylphenyl)-N...

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Bibliographic Details
Published in:Journal of applied physics 2018-01, Vol.123 (2)
Main Authors: Kasparek, Christian, Rörich, Irina, Blom, Paul W. M., Wetzelaer, Gert-Jan A. H.
Format: Article
Language:English
Subjects:
Applied physics
Bisphenol A
Carrier recombination
Crosslinking
Current efficiency
Diodes
Efficiency
High voltages
Light emitting diodes
Low voltage
Multilayers
Organic light emitting diodes
Polyphenylene vinylene
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Summary:By blending semiconducting polymers with the cross-linkable matrix ethoxylated-(4)-bisphenol-a-dimethacrylate (SR540), an insoluble layer is acquired after UV-illumination. Following this approach, a trilayer polymer light-emitting diode (PLED) consisting of a blend of poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)-benzidine] (poly-TPD) and SR540 as an electron-blocking layer, Super Yellow-Poly(p-phenylene vinylene) (SY-PPV) blended with SR540 as an emissive layer, and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as a hole-blocking layer is fabricated from solution. The trilayer PLED shows a 23% increase in efficiency at low voltage as compared to a single layer SY-PPV PLED. However, at higher voltage, the advantage in current efficiency gradually decreases. A combined experimental and modelling study shows that the increased efficiency is not only due to the elimination of exciton quenching at the electrodes but also due to suppressed nonradiative trap-assisted recombination due to carrier confinement. At high voltages, holes can overcome the hole-blocking barrier, which explains the efficiency roll-off.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5007329