Jiao Xuechen, Statz Martin, Lai Lianglun, Schott Sam, Jellett Cameron, McCulloch Iain, Sirringhaus Henning, McNeill Christopher R
Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia.
Australian Synchrotron, Clayton, Victoria 3168, Australia.
J Phys Chem B. 2020 Nov 19;124(46):10529-10538. doi: 10.1021/acs.jpcb.0c06763. Epub 2020 Nov 10.
The crystallization and aggregation behaviors of semiconducting polymers play a critical role in determining the ultimate performance of optoelectronic devices based on these materials. Due to the soft nature of polymers, crystallite imperfection exists ubiquitously. To this aspect, crystallinity is often used to represent the degree of crystallite imperfection in a reciprocal relation. Despite of the importance, the discussion on crystallinity is still on the phenomenological level and ambiguous in many cases. As two major contributors to crystallite imperfection, crystallite size and paracrystallinity are highly intertwined and hardly separated, hindering more accurate and trustworthy structural analysis. Herein, with the aid of synchrotron-based X-ray diffraction, combined with environmentally controlled heating capability, the evolution of crystallite size and paracrystallinity of two prototypical polythiophene-based thin films have been successfully measured. Strikingly, the paracrystallinity of poly(3-hexylthiophene-2,5-diyl) (P3HT) crystallites remains unchanged with annealing, while the paracrystallinity of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-]thiophene] (PBTTT) becomes diminished with crystallite growth. This work delivers a promising gesture to semiconducting polymers community, confirming that it is possible to experimentally separate crystallite size and paracrystallinity, both of which are highly intertwined. With this progress, investigation on the correlation between further detailed microstructural parameters and device performance can be achieved.
半导体聚合物的结晶和聚集行为在决定基于这些材料的光电器件的最终性能方面起着关键作用。由于聚合物的柔软性质，微晶缺陷普遍存在。在这方面，结晶度常被用来以反比关系表示微晶缺陷的程度。尽管其很重要，但关于结晶度的讨论仍停留在现象学层面，并且在很多情况下含糊不清。作为微晶缺陷的两个主要成因，微晶尺寸和准结晶度高度交织且难以分离，这阻碍了更准确和可靠的结构分析。在此，借助基于同步加速器的X射线衍射，并结合环境可控加热能力，成功测量了两种典型的聚噻吩基薄膜的微晶尺寸和准结晶度的演变。引人注目的是，聚（3-己基噻吩-2,5-二亚基）（P3HT）微晶的准结晶度在退火时保持不变，而聚[2,5-双（3-十四烷基噻吩-2-基）噻吩并[3,2-b]噻吩]（PBTTT）的准结晶度随着微晶生长而降低。这项工作为半导体聚合物领域带来了一个充满希望的进展，证实了在实验上分离高度交织的微晶尺寸和准结晶度是可能的。有了这一进展，就可以进一步研究更详细的微观结构参数与器件性能之间的相关性。
