Organic semiconductors are intensively studied as promising materials for the realisation of low-cost flexible electronic devices. The flexibility requirement implies either performance stability towards deformation, or conversely, detectable response to the deformation itself. The knowledge of the electromechanical response of organic semiconductors to external stresses is therefore not only interesting from a fundamental point of view, but also necessary for the development of real world applications. To this end, in this work we predict and measure the variation of charge carrier mobility in rubrene single crystals as a function of mechanical strain, applied selectively along the crystal axes. We find that strain induces simultaneous mobility changes along all three axes, and that in some cases the response is higher along directions orthogonal to the mechanical deformation. These variations cannot be explained by the modulation of intermolecular distances, but only by a more complex molecular reorganisation, which is particularly enhanced, in terms of response, by π-stacking and herringbone stacking. This microscopic knowledge of the relation between structural and mobility variations is essential for the interpretation of electromechanical measurements for crystalline organic semiconductors, and for the rational design of electronic devices.

中文翻译：

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红宝石单晶中异常的机电响应†

作为实现低成本柔性电子设备的有前途的材料，有机半导体得到了广泛的研究。柔韧性要求意味着对变形的性能稳定性，或者相反，对变形本身的可检测响应。因此，不仅从基本的观点出发，对有机半导体对外部应力的机电响应的了解不仅令人感兴趣，而且对于开发实际应用也十分必要。为此，在这项工作中，我们预测并测量了沿晶轴选择性施加的红荧烯单晶中的载流子迁移率随机械应变的变化。我们发现，应变会引起沿所有三个轴的同时迁移率变化，并且在某些情况下，沿着与机械变形正交的方向的响应较高。这些变化不能通过分子间距离的调节来解释，而只能通过更复杂的分子重组来解释，这在响应方面通过π堆积和人字形堆积而得到特别增强。有关结构和迁移率变化之间关系的微观知识对于解释晶体有机半导体的机电测量结果以及电子设备的合理设计至关重要。