共轭分子自身结构转变对结晶形貌及电学性能的影响

Effects of molecular topological transformation on crystallization and electric properties

在共轭光电材料的应用中,材料的溶解度决定着其加工性能,而分子规则的自组装排列对于其在固态中的结晶性起着重要作用。然而如何保证材料同时具有高的溶解度和结晶性是目前共轭有机半导体研究的一个难点。本工作选择两个相似共轭分子进行研究,其中:一个是平面结构,另一个是扭曲结构。结果发现扭曲结构分子不仅溶解度比平面结构分子大,而且在固态状态下,会自发转变成平面结构获得更好的结晶性。进一步研究分子薄膜器件的微纳结构对电学性能的影响。结果表明扭曲分子的场效应晶体管性能优于平面分子,迁移率达到6.73×10^(-3)cm^2/V·s,比平面分子薄膜的迁移率高出一个数量级。本文揭示分子结构、聚集态结构与电学性能之间的关系,为未来设计合成高效共轭分子提供了新思路。

Organic semiconductors have received much attention from both industry and academia, due to their potential opto-electronic applications. Solution-process ability is one of their most attractive features. The other component of an organic semiconductor material＇s molecular structure is its π- conjugated backbone, which plays an important role in determining the extent of π-π stacking and charge mobility. In our work, two conjugated molecules were selected to understand how molecular shape impacts the crystallization tendencies of molecular semiconductors. One （DT） is a highly tor- sional molecule, and the other molecule （CDT） uses a carbon ＂bridge＂ to lock the conjugated backbone into a planar conformation. The twisted molecule （DT） is more soluble in the solution. Interestingly, the twisted molecule （DT） exhibits a greater degree of crystallization and higher charge mobility properties in the solid state than the planar CDT molecule. The mobility of DT film is up to 6.73×10-3 cm2/V · s, which is over one order of magnitude.These findings are relevant within the context of selecting and designing semiconductors that exhibit high solubility and a tendency to provide stable organized structures with desirable electronic properties.