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Highly Efficient Electrophosphorescence from a Grafted Biscyclometalated Iridium Complex with Triarylamine Unit in Polymer Light-Emitting Devices |
| ZHU Mei-Xiang1;WU Zhong-Lian1;JIANG Chang-Yun2;LIU Jian1;LI Jian-Ren1;XING Kong-Qiang3;YANG Yu-Ping1;GAN Quan1,
CAO Yong2;ZHU Wei-Guo1 |
| 1College of Chemistry, Xiangtan University, Xiangtan 411105
2IPOMD, South China University of Technology, Guangzhou 510640
3Department of Chemistry, Qiongzhou University, Wuzhishan 572200 |
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| Cite this article: |
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ZHU Mei-Xiang, WU Zhong-Lian, JIANG Chang-Yun et al 2005 Chin. Phys. Lett. 22 1793-1796 |
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Abstract The electroluminescence performance from a novel grafted cyclometalated iridium complex (BuPhNPPy)$_{2}$Ir(acac) with triarylmine unit, where BuPhNPPy is N,N-di(4-tert-butylphenyl)-4-(2-pyridyl) phenylamine and Hacac is acetylacetone, is demonstrated in the double-layered polymer light-emitting devices (PLEDs). The PLEDs emit intense green phosphorescence at 533nm with a shoulder peak of 566nm employing 4wt.% (BuPhNPPy)2Ir(acac) doped a blend of poly(vinylcarbazole) (PVK) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) as the emitting layer. A maximum luminance of 14610cd/m2 at voltage of 24V and a maximum external quantum efficiency Eext of 10.4% photons per electron (ph/el) at current density of 32mA/cm2 are achieved. When the current density is raised to 100mA/cm2, Eext of the device still remained to 8.3% ph/el. This indicates that the triplet--triplet annihilation is restrained more effectively at high current density. The improvement of electrophosphorescence performances of the iridium complex may be contributed to an ortho-substituent effect of grafted triarylmine unit.
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| Keywords:
78.60.Fi
78.66.Qn
85.06.Jb
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Published: 01 July 2005
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