Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Angew Chem Int Ed Engl. 2017 Jul 10;56(29):8402-8406. doi: 10.1002/anie.201610727. Epub 2017 Feb 7.
The effect of varying the emitter concentration on the structural properties of an archetypal phosphorescent blend consisting of 4,4'-bis(N-carbazolyl)biphenyl and tris(2-phenylpyridyl)iridium(III) has been investigated using non-equilibrium molecular dynamics (MD) simulations that mimic the process of vacuum deposition. By comparison with reflectometry measurements, we show that the simulations provide an accurate model of the average density of such films. The emitter molecules were found not to be evenly distributed throughout film, but rather they can form networks that provide charge and/or energy migration pathways, even at emitter concentrations as low as ≈5 weight percent. At slightly higher concentrations, percolated networks form that span the entire system. While such networks would give improved charge transport, they could also lead to more non-radiative pathways for the emissive state and a resultant loss of efficiency.
使用非平衡分子动力学（MD）模拟来模拟真空沉积过程，研究了发射极浓度对由 4,4'-双（N-咔唑基）联苯和三（2-苯基吡啶基）铱（III）组成的典型磷光体混合物的结构性质的影响。通过与反射率测量的比较，我们表明模拟提供了此类薄膜的平均密度的准确模型。发现发射极分子并非均匀分布在整个薄膜中，而是可以形成网络，甚至在发射极浓度低至约 5 重量％时，也可以提供电荷和/或能量迁移途径。在稍高的浓度下，形成了贯穿整个系统的渗滤网络。虽然这样的网络会改善电荷输运，但它们也可能为发射态提供更多的非辐射途径，并导致效率降低。
