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The Molecular Origin of Anisotropic Emission in an Organic Light-Emitting Diode
Nano Letters ( IF 10.8 ) Pub Date : 2017-09-18 00:00:00 , DOI: 10.1021/acs.nanolett.7b03528
Thomas Lee , Bertrand Caron , Martin Stroet , David M. Huang 1 , Paul L. Burn , Alan E. Mark
Affiliation  

Atomistic nonequilibrium molecular dynamics simulations have been used to model the induction of molecular orientation anisotropy within the emission layer of an organic light-emitting diode (OLED) formed by vapor deposition. Two emitter species were compared: racemic fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3) and trans-bis(2-phenylpyridine)(acetylacetonate)iridium(III) (Ir(ppy)2(acac)). The simulations show that the molecular symmetry axes of both emitters preferentially align perpendicular to the surface during deposition. The molecular arrangement formed on deposition combined with consideration of the transition dipole moments provides insight into experimental reports that Ir(ppy)3 shows isotropic emission, while Ir(ppy)2(acac) displays improved efficiency due to an apparent preferential alignment of the transition dipole vectors parallel to the substrate. The simulations indicate that this difference is not due to differences in the extent of emitter alignment, but rather differences in the direction of the transition dipoles within the two complexes.

中文翻译:

有机发光二极管中各向异性发射的分子起源

原子非平衡分子动力学模拟已用于模拟通过气相沉积形成的有机发光二极管(OLED)的发射层内分子取向各向异性的诱导。比较了两种发射体:外消旋fac-三(2-苯基吡啶)铱(III)(Ir(ppy)3)和反式双(2-苯基吡啶)(乙酰丙酮)铱(III)(Ir(ppy)2(acac ))。仿真表明,在沉积过程中,两个发射器的分子对称轴优先垂直于表面对齐。结合沉积偶极矩的考虑,在沉积过程中形成的分子排列提供了对Ir(ppy)3的实验报告的深入了解显示出各向同性的发射,而Ir(ppy)2(acac)则显示出效率提高,这是因为过渡偶极子矢量与基板平行时出现了明显的优先排列。仿真表明,这种差异不是由于发射极对准程度的差异,而是两种复合物中过渡偶极子方向的差异。
更新日期:2017-09-18
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