Transport in Twisted Crystalline Charge Transfer Complexes
Transport in Twisted Crystalline Charge Transfer Complexes
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DOI：
10.1021/acs.chemmater.1c04003
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发表时间：
2022-02-22
影响因子：
8.6
通讯作者：
Kahr, Bart
中科院分区：
文献类型：
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作者：
Yang, Yongfan;Zhang, Yuze;Kahr, Bart
许多晶体从熔体中生长为带状球晶，具有指示螺旋扭曲的光学节奏。在这项工作中，23的41个电荷转移复合物（CTC）生长扭曲的形态。作为一个群体，CTC比我们先前研究中任意选择的分子晶体（31%）更常见地扭曲（56%）。为了分析扭转对电荷传输的影响，表征了具有菲（PhT）、芘（PyT）和二萘嵌苯的三种基于四氰基乙烯的CTC。PhT和PyT使用有机场效应晶体管进行迁移率测量。扭曲晶体的迁移率大约是没有表面光学调制的晶体的三倍，而没有表面光学调制的晶体实际上是直的。基于密度泛函理论计算了直晶体和扭曲晶体迁移率的差异。从晶体学信息文件中建立的直晶体模型进行了计算，并提出了各向异性的空穴和电子输运。对于扭曲晶体模型，超晶胞中的相邻层围绕实验确定的扭曲方向旋转0.01度。修正的转移积分导致扭曲晶体的计算迁移率略有增加（高达25%）。对单个原纤的模型计算和对原纤集合的测量的比较表明，单晶之间的界面可能是相应的。
Many crystals grow as banded spherulites from the melt with an optical rhythm indicative of helicoidal twisting. In this work, 23 of 41 charge transfer complexes (CTCs) are grown with twisted morphologies. As a group, CTCs more commonly twist (56%) than molecular crystals arbitrarily chosen in our previous research (31%). To analyze the effect of twisting on charge transport, three tetracyanoethylene-based CTCs with phenanthrene (PhT), pyrene (PyT), and perylene are characterized. PhT and PyT are subject to mobility measurements using organic field-effect transistors. The mobilities for twisted crystals are around three times higher than for crystals with no ostensible optical modulation, which are effectively straight. The differences in mobilities of straight and twisted crystals are considered computationally based on density functional theory. Straight crystal models built from crystallographic information files are calculated and present anisotropic hole and electron transport. For twisted crystal models, adjacent layers in the supercell are rotated by 0.01 degrees around experimentally determined twisting directions. The modified transfer integrals lead to a slight increase (up to 25%) in the calculated mobilities of twisted crystals. Comparisons of model calculations on individual fibrils and measurements of ensembles of fibrils indicate that interfaces between single crystals are likely consequential.