Jiang J, Walters D M, Zhou D, Ediger M D
Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China.
Soft Matter. 2016 Apr 7;12(13):3265-70. doi: 10.1039/c6sm00262e. Epub 2016 Feb 29.
Vapor-deposited glasses can be anisotropic and molecular orientation is important for organic electronics applications. In organic light emitting diodes (OLEDs), for example, the orientation of dye molecules in two-component emitting layers significantly influences emission efficiency. Here we investigate how substrate temperature during vapor deposition influences the orientation of dye molecules in a model two-component system. We determine the average orientation of a linear blue light emitter 1,4-di-[4-(N,N-diphenyl)amino]styryl-benzene (DSA-Ph) in mixtures with aluminum-tris(8-hydroxyquinoline) (Alq3) by spectroscopic ellipsometry and IR dichroism. We find that molecular orientation is controlled by the ratio of the substrate temperature during deposition and the glass transition temperature of the mixture. These findings extend recent results for single component vapor-deposited glasses and suggest that, during vapor deposition, surface mobility allows partial equilibration towards orientations preferred at the free surface of the equilibrium liquid.
气相沉积玻璃可能具有各向异性，并且分子取向对于有机电子应用很重要。例如，在有机发光二极管（OLED）中，双组分发光层中染料分子的取向会显著影响发光效率。在此，我们研究气相沉积过程中的衬底温度如何影响模型双组分体系中染料分子的取向。我们通过椭圆偏振光谱法和红外二色性确定了线性蓝光发射体1,4 - 二 - [4 - （N，N - 二苯基）氨基]苯乙烯基苯（DSA - Ph）与三（8 - 羟基喹啉）铝（Alq3）混合物中的平均取向。我们发现分子取向由沉积过程中的衬底温度与混合物的玻璃化转变温度之比控制。这些发现扩展了近期关于单组分气相沉积玻璃的结果，并表明在气相沉积过程中，表面迁移率使得能够部分平衡至平衡液体自由表面处优先的取向。
