Cavendish Laboratory, JJ Thomson Avenue, Cambridge-CB3 0HE, U.K.
ACS Nano. 2011 Jan 25;5(1):329-36. doi: 10.1021/nn102899g. Epub 2010 Dec 28.
Demixed blends of poly[3-hexylthiophene] (P3HT) and C₆₁-butyric acid methyl ester (PCBM) are widely used in photovoltaic diodes (PV) and show excellent quantum efficiency and charge collection properties. We find the empirically optimized literature process conditions give rise to demixing during solvent (chlorobenzene) evaporation by spinodal decomposition. Ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS) results are consistent with the formation of 1-2 nm thick surface layers on both interfaces, which trigger the formation of surface-directed waves emanating from both film surfaces. This observation is evidence that spinodal demixing (leading to a bicontinuous phase morphology) precedes the crystallization of the two components. We propose a model for the interplay of demixing and crystallization which explains the broadly similar PV performance for devices made with the bottom electrodes either as hole or electron collector. The process regime of temporal separation of demixing and crystallization is attractive because it provides a way to control the morphology and thereby the efficiency of PV devices.
聚[3-己基噻吩]（P3HT）和 C₆₁-丁酸甲酯（PCBM）的混合物广泛用于光伏二极管（PV），并显示出优异的量子效率和电荷收集性能。我们发现，经验优化的文献工艺条件会导致溶剂（氯苯）蒸发时通过旋节分解产生相分离。紫外光电子能谱（UPS）和 X 射线光电子能谱（XPS）结果一致表明，在两个界面上形成了 1-2nm 厚的表面层，这引发了源自两个膜表面的表面导向波的形成。这一观察结果表明，旋节分解（导致双连续相形态）先于两种成分的结晶。我们提出了一个关于相分离和结晶相互作用的模型，该模型解释了具有底部电极作为空穴或电子收集器的器件具有广泛相似的 PV 性能的原因。相分离和结晶的时间分离过程很有吸引力，因为它提供了一种控制形态从而控制 PV 器件效率的方法。
