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P‐168: Investigation of High‐Efficiency Electrophosphorescent Organic Light‐emitting Diodes with Double‐Emission Layers
Author(s) -
Sun Jiaxin,
Zhu Xiuling,
Yu Xiaoming,
Wong Man,
Kwok HoiSing
Publication year - 2007
Publication title -
sid symposium digest of technical papers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.351
H-Index - 44
eISSN - 2168-0159
pISSN - 0097-966X
DOI - 10.1889/1.2785435
Subject(s) - iridium , quantum efficiency , oled , luminous efficacy , materials science , optoelectronics , doping , diode , luminous flux , annihilation , phosphorescence , exciton , current density , optics , fluorescence , chemistry , physics , layer (electronics) , nanotechnology , condensed matter physics , light source , biochemistry , quantum mechanics , catalysis
Highly efficient electrophosphorescent organic light‐emitting diodes (PHOLEDs) with double‐emission layers by doping both hole‐ and electron‐transport hosts with green dye bis(2‐phenylpyridine)iridium(III)acetylacetonate [(ppy) 2 Ir(acac)] have been fabricated and investigated. In particular, the dependence of performance characteristics on the thickness and doping concentration of the double‐emission layers is studied. By fine tuning these two parameters a peak luminous efficiency of 77cd/A, corresponding to 20.5% external quantum efficiency (EQE), is achieved at a current density of 0.053mA/cm 2 from the optimized device. Even at 1000cd/m 2 , it still shows very high luminous efficiency of 71cd/A, with a power efficiency of 40lm/W. A shifting exciton formation zone with the driving current as well as triplet‐triplet annihilation can explain the efficiency profile observed experimentally.