Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5399791 | Journal of Luminescence | 2014 | 21 Pages |
Abstract
High-performance phosphorescent organic light-emitting diodes (PhOLEDs) by using dual-emissive-layer (DEL) structure to reduce efficiency roll-off were fabricated. The DEL was comprised of a hole-transport-type host of N, Nâ²-bis(naphthalen-1-yl)-N, Nâ²-bis(phenyl)-benzidine (NPB) and a bipolar host of 4,4â²-bis(carbazol-9-yl)biphenyl (CBP), which were both doped with an orange phosphorescent dopant of bis[2-(4-tert-butylphenyl)-benzothiazolato-N,C2â²]iridium (acetylacetonate) [(t-bt)2Ir(acac)]. After the optimization of doping concentration of the first emissive layer (FEL), the device with DEL exhibited 11% lower roll-off power efficiency than single emissive layer devices (SED) when the luminance increased from 1000Â cd/m2 to 10,000Â cd/m2. The hole-electron recombination zone in DEL was illuminated by inserting an ultrathin fluorescent probe of 4-(dicyanomethylene)-2-tert-butyl-6 (1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) in different emissive regions. The performance improvement was attributed to the optimization of energy barrier and the expansion of exciton formation zone within the DEL.
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Authors
Zhu Ma, Shunliang Zhou, Song Hu, Junsheng Yu,