Department of Physics and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom.
J Am Chem Soc. 2011 Jun 29;133(25):9834-43. doi: 10.1021/ja2013104. Epub 2011 Jun 8.
The nature of main in-plane skeleton Raman modes (C=C and C-C stretch) of poly(3-hexylthiophene) (P3HT) in pristine and its blend thin films with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) is studied by resonant and nonresonant Raman spectroscopy and Raman simulations. Under resonant conditions, the ordered phase of P3HT with respect to its disordered phase is identified by (a) a large shift in the C=C mode peak position to lower wavenumber (21 cm(-1) shift), (b) a narrower fwhm of the C=C mode (9 cm(-1) narrower), (c) a larger intensity of the C-C mode relative to the C=C mode (56% larger), and (d) a very small Raman dispersion (5 cm(-1)) of the C=C mode. The behavior of the C=C and C-C modes of the ordered and disordered phases of P3HT can be explained in terms of different molecular conformations. The C=C mode of P3HT in P3HT:PCBM blend films can be reproduced by simple superposition of the two peaks observed in different phases of P3HT (ordered and disordered). We quantify the molecular order of P3HT after blending with PCBM and the subsequent thermal annealing to be 42 ± 5% and 94 ± 5% in terms of the fraction of ordered P3HT phase, respectively. The increased molecular order of P3HT in blends upon annealing correlates well with enhanced device performance (J(SC), -4.79 to -8.72 mA/cm(2) and PCE, 1.07% to 3.39%). We demonstrate that Raman spectroscopy (particularly under resonant conditions) is a simple and powerful technique to study molecular order of conjugated polymers and their blend films.
聚 3-己基噻吩（P3HT）在原始及其与[6,6]-苯基-C（61）-丁酸甲酯（PCBM）的共混薄膜中的面内主骨架拉曼模式（C=C 和 C-C 伸缩）的性质通过共振和非共振拉曼光谱和拉曼模拟进行研究。在共振条件下，通过以下方法确定 P3HT 的有序相与无序相的关系：（a）C=C 模式峰位置向低波数的较大偏移（21 cm(-1)的偏移），（b）C=C 模式的较窄半峰全宽（9 cm(-1)的变窄），（c）C-C 模式相对于 C=C 模式的较大强度（56%的增加），以及（d）C=C 模式的非常小的拉曼色散（5 cm(-1)）。有序相和无序相的 P3HT 的 C=C 和 C-C 模式的行为可以用不同的分子构象来解释。P3HT:PCBM 共混薄膜中 P3HT 的 C=C 模式可以通过观察到的 P3HT 不同相（有序相和无序相）的两个峰的简单叠加来重现。我们以有序 P3HT 相的分数为单位，定量计算了与 PCBM 混合后和随后热退火后 P3HT 的分子有序度，分别为 42 ± 5%和 94 ± 5%。退火后共混物中 P3HT 的分子有序度增加与器件性能的提高（J(SC)，-4.79 至-8.72 mA/cm(2)和 PCE，1.07%至 3.39%）密切相关。我们证明了拉曼光谱（特别是在共振条件下）是研究共轭聚合物及其共混薄膜的分子有序度的一种简单而强大的技术。
