Time-resolved light scattering studies of phase separation in thin film semiconducting polymer blends during spin-coating
Time-resolved light scattering studies of phase separation in thin film semiconducting polymer blends during spin-coating
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DOI：
10.1021/ma0477145
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发表时间：
2005-03-22
期刊：
影响因子：
5.5
通讯作者：
Jones, RAL
中科院分区：
文献类型：
--
作者：
Jukes, PC;Heriot, SY;Jones, RAL
不相容的半导体聚合物的共混物的薄膜在有机电子器件如LED和光致发光器件中具有技术应用，其中更有效的器件可以通过共混两种或更多种聚合物以结合联合收割机有利的电子性质来生产。1这些薄膜通常通过旋涂形成，并且在快速去除溶剂期间表现出由相分离形成的复杂横向结构。这在整个膜中产生界面的分布，这对于器件可能是有益的，因为电荷缔合和解离主要发生在界面处。2、3相分离结构的形态和尺寸可以对器件的性能具有深远的影响，因此，更好地理解相分离的机制应该允许合理设计工艺路线以获得最佳器件性能。用两种不混溶的聚合物在普通溶剂中的溶液淹没涂覆基材，并以每分钟几千转的速度旋转，一下在此过程的早期阶段，大部分溶液被抛弃，在基底上留下薄的流体层。该层随后变薄，首先由于流体流动，然后通过溶剂蒸发。5随着溶剂蒸发，系统将从三元（聚合物/聚合物/溶剂）相图的单相区域过渡到两相区域。旋转浇铸这种混合物的最终结果通常是具有侧域的良好限定的形貌结构的薄膜，其可以使用诸如原子力显微镜（AFM）的技术成像。一些研究已经调查了从二元和三元聚合物共混物中除去溶剂引起的相分离形态。Dalnoki-Veress等人6研究了聚苯乙烯/聚异戊二烯和聚苯乙烯/聚（甲基丙烯酸甲酯）（PS/PMMA）共混物的平均畴面积与组成和纺丝速度的函数关系。Walheim等人7提出，PS/PMMA共混物中相之间的高度差可以由两种聚合物在共同溶剂中的相对溶解度来解释。几种不同的模型也被提出来试图解释所观察到的结构形成在旋转浇铸聚合物共混物。Tanaka等人8提出，较低表面能组分对表面的不完全润湿将迫使较高表面能组分从膜表面突出。Ton-That等人认为，
Thin films of blends of incompatible semiconducting polymers find technological applications in organic electronic devices, such as LEDs and photovoltaics, where a more efficient device can be produced by blending two or more polymers to combine favorable electronic properties. 1 These films are usually formed by spin-coating and exhibit complex lateral structures formed by phase separation during the rapid removal of solvent. This produces a distribution of interfaces throughout the film, which can be beneficial for devices since charge association and dissociation occur primarily at the interfaces. 2, 3 The morphology and size of the phase-separated structures can have a profound effect on the properties of the device, 4 so a better understanding of mechanisms of phase separation should permit the rational design of processing routes for optimum device performance.In spin-coating a substrate is flooded with a solution of the two immiscible polymers in a common solvent and spun round at a rate of a few thousand revolutions per minute. Most of the solution is cast off during the early stages of this process, leaving a thin fluid layer on the substrate. This layer subsequently thins, first due to fluid flow and later by solvent evaporation. 5 As the solvent evaporates, the system will cross from a onephase region of the ternary (polymer/polymer/solvent) phase diagram to a two-phase region. The final result of spin-casting such a mixture is usually a thin film with a well-defined topographical structure of lateral domains, which can be imaged using techniques such as atomic force microscopy (AFM). Several studies have investigated the phase separation morphology induced by removal of solvent from binary and ternary polymer blends. Dalnoki-Veress et al. 6 investigated the average domain area as a function of composition and spin speed for blends of polystyrene/polyisoprene and polystyrene/poly (methyl methacrylate)(PS/PMMA). Walheim et al. 7 proposed that the height difference between phases in PS/PMMA blends can be accounted for by the relative solubilities of the two polymers in the common solvent. Several different models have also been proposed in attempts to explain the observed structure formation in spin-cast polymer blends. Tanaka et al. 8 proposed that incomplete wetting of the surface by the lower surface energy component will force the higher surface energy component to protrude from the film surface. Ton-That et al. 9 argued