Drastic drop of external quantum efficiency at liquid nitrogen temperature in a bilayer blue phosphorescent organic light-emitting device

•We developed highly efficient bilayer blue phosphorescent OLEDs.•External quantum efficiency (EQE) was 17.2% at room temperature.•EQE drastically drops to 0.8% at liquid nitrogen temperature.•The drop of EQE was critically dependent on the TAZ layer. We have investigated substantial drop of externa...

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Bibliographic Details
Published in:Synthetic metals 2016-07, Vol.217, p.244-247
Main Authors: Ha, Mi-Young, Park, Da-Young, Lee, Min-Jae, Choi, Seung-Jung, Jung, Jae-Hoon, Moon, Dae-Gyu
Format: Article
Language:English
Subjects:
Bilayer
Blue
Liquid nitrogen temperature
OLED
Phosphorescence
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Summary:•We developed highly efficient bilayer blue phosphorescent OLEDs.•External quantum efficiency (EQE) was 17.2% at room temperature.•EQE drastically drops to 0.8% at liquid nitrogen temperature.•The drop of EQE was critically dependent on the TAZ layer. We have investigated substantial drop of external quantum efficiency (EQE) at liquid nitrogen temperature in a bilayer blue phosphorescent organic light emitting device with a structure of ITO/TAPC:FIrpic/TAZ/LiF/Al, where TAPC, FIrpic, and TAZ represent 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane, iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate, and 3-(biphenyl-4-yl)-4-phenyl-5-(4-tert-butyl-phenyl)-1,2,4-triazole, respectively. The device exhibits a high EQE of 17.2% at room temperature although it has a simple bilayer structure. However, the quantum efficiency drops drastically to 0.8% at liquid nitrogen temperature. We studied this drastic drop of EQE in viewpoints of carrier conduction, carrier recombination, photoluminescence quantum efficiency, and energy transfer.
ISSN:0379-6779
1879-3290
DOI:10.1016/j.synthmet.2016.04.010