Molecular and Electronic Structure in Thin Films of Semiconducting Polymers as Studied in the Infrared and UV/Vis Spectral Range

半导体聚合物联合收割机结合了纯聚合物的优点，例如机械坚固性和重量轻，具有半导体电子特性和低成本大面积沉积的可能性，这提供了相当大的技术益处。尽管在有机电子领域的深入研究和有机发光二极管（OLED）的商业成功，许多非常基本的问题仍然没有答案。例如，在良好有序的有机半导体膜中，电荷和激子被认为是高度有序的无机半导体之间的中间体，具有带状传输，以及具有跳跃传输的非常无序的系统。然而，我们还不知道如何控制该结构以改善电荷或激子相干长度。这种缺乏理解的部分原因是缺乏合适的微结构探针，对纳米尺度上的无序敏感。在这个项目中，建议建立在莱比锡大学最近的工作，使用红外跃迁矩取向分析（IR-TMOA）来探测有机半导体中亚分子结构的部分特定取向和顺序。这种技术-到目前为止是独一无二的，只有在莱比锡可用-能够建立一个全面的图片的结构和无序程度的长度尺度相关的能量和电荷转移。使用时间分辨光谱测量在谢菲尔德大学，从IR-TMOA的微观结构的调查结果将与激子和电荷转移相干长度的测量。计划在模型聚合物P3 HT及其新型瓶刷衍生物上进行测量。结晶度和微观结构环境将被分子量和化学结构改变。此外，模型共聚物PNDIT 2（或P（NDI 2 OD-T2））及其硫代衍生物2S-trans-PNDIT 2允许研究化学取代的影响，并因此改变分子轨道能级对分子取向和顺序以及电荷转移和激子相干长度的影响。到目前为止，这种实验技术的结合以前还没有发表过，并承诺对分子结构和电子性质的相互作用的新见解。除了使用时间分辨光谱和稳态IR-TMOA作为独立的方法外，计划将TMOA的测量原理与时间分辨红外光谱相结合。这将导致第一次的测量技术，允许研究动态的取向和秩序的分子单位。

Semiconducting polymers combine advantages of neat polymers, such as mechanical robustness and light weight, with semiconducting electronic characteristics and the possibility of low-cost large-area deposition, which provides considerable technological benefits. Despite the intensive research in the field of organic electronics and the commercial success of organic light emitting diodes (OLEDs), many very fundamental questions remain unanswered. For example, in well-ordered organic semiconductor films charges and excitons are thought to behave as intermediate between highly ordered inorganic semiconductors, with band-like transport, and very disordered systems with hopping transport. However, we do not yet understand how the structure can be controlled to improve charge or exciton coherence length. This lack of understanding is in part due to the lack of suitable microstructural probes that are sensitive to disorder on the nanometer scale. In this project, it is propose to build up upon recent work at Leipzig University using infrared transition moment orientational analysis (IR-TMOA) to probe the moiety-specific orientation and order of sub-molecular structures in organic semiconductors. This technique –so far unique and only available in Leipzig– enables to build up a comprehensive picture of the structure and the degree of disorder at the length scale relevant for energy and charge transfer. Using time-resolved spectroscopy measurements at the University of Sheffield, the microstructural findings from IR-TMOA will be correlated with measurements of the exciton and charge transfer coherence length. Measurements are planned to be examined at the model polymer P3HT and their novel bottlebrush derivatives. The degree of crystallinity and the microstructural environment will be altered by the molecular weight and chemical structure. Furthermore, the model co-polymer PNDIT2 (or P(NDI2OD-T2)) and its thionated derivative 2S-trans-PNDIT2 allows for studying the influence of chemical substitution and hence altered molecular orbital energy levels on the molecular orientation and order as well as charge transfer and exciton coherence length. So far this combination of experimental techniques has not been published previously and promises new insights into the interplay of molecular structure and electronic properties. In addition to the use of time-resolved spectroscopy and steady-state IR-TMOA as independent methods, it is planned to combine the measurement principle of TMOA with time-resolved infrared spectroscopy. This will lead for the first time to a measurement technique which allows for studying the dynamics of orientation and order of molecular units.