Department of Chemistry and Chemical Biology, MSC03 2060, University of New Mexico, Albuquerque, New Mexico 87110, USA.
J Chem Phys. 2013 Jul 28;139(4):044903. doi: 10.1063/1.4815819.
Resonance Raman spectra of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester blend thin films display progressions of overtone and combination bands (up to two harmonics) involving the dominant symmetric C=C backbone stretching mode of P3HT that encode excited state vibrational displacements and dynamics information. Contributions from both crystalline (aggregated) and amorphous (unaggregated) P3HT domains are resolved and intensities are analyzed using the time-dependent theory of spectroscopy. Raman spectra, excitation profiles, and absorption spectra are simulated with the same parameters using a single electronic state description for each P3HT form. Time-dependent wavepacket overlaps expose vibrational coherence on sub-100 fs timescales, which is usually difficult to extract from conventional ultrafast pump-probe spectra and transients of polymer∕fullerene blends. The results demonstrate the potential of simpler CW resonance Raman approaches to uncover excited state geometry changes and early vibrational dynamics from distinct morphological forms in polymer∕fullerene blends.
聚(3-己基噻吩)（P3HT）和[6,6]-苯基-C61-丁酸甲酯共混薄膜的共振拉曼光谱显示出泛频和组合带（高达两个谐波）的进展，涉及 P3HT 占主导地位的对称 C=C 骨架伸缩模式，这些模式编码了激发态振动位移和动力学信息。解析了来自结晶（聚集）和无定形（未聚集）P3HT 域的贡献，并使用时间相关光谱理论分析了强度。使用单个电子态描述对每种 P3HT 形式进行模拟，得到了拉曼光谱、激发轮廓和吸收光谱。时变波包重叠在亚 100fs 时间尺度上暴露了振动相干性，这通常很难从传统的超快泵浦-探测光谱和聚合物/富勒烯混合物的瞬态中提取。结果表明，更简单的 CW 共振拉曼方法具有揭示聚合物/富勒烯混合物中不同形态的激发态几何变化和早期振动动力学的潜力。
