Distinguishing triplet energy transfer and trap-assisted recombination in multi-color organic light-emitting diode with an ultrathin phosphorescent emissive layer
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An ultrathin layer of deep-red phosphorescent emitter tris(1-phenylisoquinoline) iridium (III) (Ir(piq)3) is inserted within different positions of the electron blocking layer fac-tris (1-phenylpyrazolato-N,C2')-iridium(III) (Ir(ppz)3) to distinguish the contribution of the emission from the triplet exciton energy transfer/diffusion from the adjacent blue phosphorescent emitter and the trap-assisted recombination from the narrow band-gap emitter itself. The charge trapping effect of the narrow band-gap deep-red emitter which forms a quantum-well-like structure also plays a role in shaping the electroluminescent characteristics of multi-color organic light-emitting diodes. By accurately controlling the position of the ultrathin sensing layer, it is considerably easy to balance the white emission which is quite challenging for full-color devices with multiple emission zones. There is nearly no energy transfer detectable if 7 nm thick Ir(ppz)3 is inserted between the blue phosphorescent emitter and the ultrathin red emitter.
Xue , Q , Xie , G , Liu , S , Chen , P , Zhao , Y & Liu , S 2014 , ' Distinguishing triplet energy transfer and trap-assisted recombination in multi-color organic light-emitting diode with an ultrathin phosphorescent emissive layer ' Journal of Applied Physics , vol 115 , no. 11 , 114504 . DOI: 10.1063/1.4869056
Journal of Applied Physics
© 2014 AIP Publishing LLC
The authors acknowledge funds from the National Key Basic Research and Development Program of China under Grant No. 2010CB327701. Q. Xue acknowledges support from Fundamental Research Funds for the Central Universities and China Scholarship Council.
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