Current efficiency in organic light-emitting diodes with a hole-injection layer

We have systematically investigated the effect of layer structures on the current efficiency of prototypical hole-injection layer (HIL)/hole-transport layer (HTL)/electron-transport layer (ETL) organic light-emitting diodes based on 4 , 4 ′ , 4 ″ -tris[ N -(3-methylphenyl)- N -phenylamino] triphenyl...

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Published in:Applied physics letters 2008-09, Vol.93 (9), p.093306-093306-3
Main Authors: Wang, Hui, Klubek, Kevin P., Tang, C. W.
Format: Article
Language:English
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Summary:We have systematically investigated the effect of layer structures on the current efficiency of prototypical hole-injection layer (HIL)/hole-transport layer (HTL)/electron-transport layer (ETL) organic light-emitting diodes based on 4 , 4 ′ , 4 ″ -tris[ N -(3-methylphenyl)- N -phenylamino] triphenylamine (MTDATA) as the HIL, 4 , 4 ′ -bis[ N -(1-naphthyl)- N -phenylamino]biphenyl (NPB) as the HTL, and tris(8-quinolinolato)aluminum (Alq) as the ETL. With bilayer devices, the current efficiency is limited by exciplex emissions in the case of MTDATA/Alq and quenching of Alq emissions by NPB + radical cations in NPB/Alq. The improved current efficiency in trilayer MTDATA/NPB/Alq devices can be attributed to a reduction in NPB + radical cations at the NPB/Alq interface and a strong electric field in the NPB layer.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.2978349