Gann Eliot, McNeill Christopher R, Szumilo Monika, Sirringhaus Henning, Sommer Michael, Maniam Subashani, Langford Steven J, Thomsen Lars
Department of Materials Engineering, Monash University, Wellington Road, Clayton, Victoria 3800, Australia.
Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
J Chem Phys. 2014 Apr 28;140(16):164710. doi: 10.1063/1.4871463.
Near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy is an important tool for probing the structure of conjugated polymer films used in organic electronic devices. High-performance conjugated polymers are often donor-acceptor co-polymers which feature a repeat unit with multiple functional groups. To facilitate better application of NEXAFS spectroscopy to the study of such materials, improved understanding of the observed NEXAFS spectral features is required. In order to examine how the NEXAFS spectrum of a donor-acceptor co-polymer relates to the properties of the sub-units, a series of naphthalene diimide-thiophene-based co-polymers have been studied where the nature and length of the donor co-monomer has been systematically varied. The spectra of these materials are compared with that of a thiophene homopolymer and naphthalene diimide monomer enabling peak assignment and the influence of inter-unit electronic coupling to be assessed. We find that while it is possible to attribute peaks within the π* manifold as arising primarily due to the naphthalene diimide or thiophene sub-units, very similar dichroism of these peaks is observed indicating that it may not be possible to separately probe the molecular orientation of the separate sub-units with carbon K-edge NEXAFS spectroscopy.
近边X射线吸收精细结构（NEXAFS）光谱是探测用于有机电子器件的共轭聚合物薄膜结构的重要工具。高性能共轭聚合物通常是供体-受体共聚物，其具有带有多个官能团的重复单元。为了促进NEXAFS光谱在这类材料研究中的更好应用，需要对观察到的NEXAFS光谱特征有更深入的理解。为了研究供体-受体共聚物的NEXAFS光谱如何与亚单元的性质相关，我们研究了一系列基于萘二酰亚胺-噻吩的共聚物，其中供体共聚单体的性质和长度已被系统地改变。将这些材料的光谱与噻吩均聚物和萘二酰亚胺单体的光谱进行比较，从而能够进行峰归属并评估单元间电子耦合的影响。我们发现，虽然有可能将π*多重态内的峰主要归因于萘二酰亚胺或噻吩亚单元，但观察到这些峰具有非常相似的二向色性，这表明用碳K边NEXAFS光谱可能无法分别探测各个亚单元的分子取向。
