Comparing the emissive dipole orientation of two similar phosphorescent green emitter molecules in highly efficient organic light-emitting diodes

被引:118
作者
Liehm, Philipp [1 ]
Murawski, Caroline [1 ]
Furno, Mauro [2 ]
Luessem, Bjoern [1 ]
Leo, Karl [1 ]
Gather, Malte C. [1 ]
机构
[1] Tech Univ Dresden, Inst Angew Photophys, D-01062 Dresden, Germany
[2] Novaled AG, D-01307 Dresden, Germany
关键词
D O I
10.1063/1.4773188
中图分类号
O59 [应用物理学];
学科分类号
摘要
We investigate the average orientation of the transition dipole moments of two green phosphorescent emitters Ir(ppy)(3) and Ir(ppy)(2)(acac) embedded in a CBP matrix, using in-situ angle resolved electroluminescence spectroscopy and optical simulations. The dipole orientation of Ir(ppy)(3) is nearly isotropic while 77% of the dipoles are horizontally aligned for Ir(ppy)(2)(acac). Optimized organic light-emitting diodes based on these emitters achieve external quantum efficiencies of 18.3% (Ir(ppy)(3)) and 21.7% (Ir(ppy)(2)(acac)). This difference is partially explained by the different dipole orientations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773188]
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