Department of Chemistry, School of Physical Sciences, The University of Adelaide , Adelaide 5005, Australia.
Nano Lett. 2017 Oct 11;17(10):6464-6468. doi: 10.1021/acs.nanolett.7b03528. Epub 2017 Sep 18.
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)) and trans-bis(2-phenylpyridine)(acetylacetonate)iridium(III) (Ir(ppy)(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) shows isotropic emission, while Ir(ppy)(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.
已使用原子非平衡分子动力学模拟来模拟通过气相沉积形成的有机发光二极管 (OLED) 的发射层中分子取向各向异性的诱导。比较了两种发射体物质：外消旋 fac-三（2-苯基吡啶）铱（III）（Ir（ppy））和反式双（2-苯基吡啶）（乙酰丙酮）铱（III）（Ir（ppy）（acac））。模拟表明，在沉积过程中，两种发射体的分子对称轴都优先垂直于表面排列。沉积过程中形成的分子排列结合跃迁偶极矩的考虑，为实验报告提供了深入的见解，即 Ir（ppy）显示各向同性发射，而 Ir（ppy）（acac）由于跃迁偶极子向量明显平行于衬底排列，显示出效率提高。模拟表明，这种差异不是由于发射体排列程度的差异，而是两个配合物中跃迁偶极子的方向差异所致。
