Charge Transport in Twisted Organic Semiconductor Crystals of Modulated Pitch
Charge Transport in Twisted Organic Semiconductor Crystals of Modulated Pitch
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DOI：
10.1002/adma.202203842
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发表时间：
2022-08-19
影响因子：
29.4
通讯作者：
Shtukenberg, Alexander G.
中科院分区：
文献类型：
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作者：
Yang, Yongfan;de Moraes, Lygia Silva;Shtukenberg, Alexander G.
许多分子晶体（约三分之一）从熔体中生长为扭曲的螺旋带，这种优势在有限类别的材料中甚至更高，例如电荷转移复合物。以前，这种复合物的扭曲微晶呈现载流子迁移率的增加。在这里，扭转对电荷迁移率的影响更好地分析了单组分有机半导体，2，5-双（3-十二烷基-2-噻吩基）-噻唑并[5，4-d]噻唑（BDT），形成扭曲的晶体与不同的螺旋节距，并使得可能的扭曲强度与载流子迁移率的相关性。薄膜进行了分析，通过X射线散射和Mueller矩阵偏振来表征多晶合奏的微观组织。当晶体以最小节距（最扭曲）生长时，有机场效应晶体管的载流子迁移率是沿着纤维伸长方向具有最大节距的晶体的载流子迁移率的五倍。沿垂直方向观察到沿着十倍增加。基于扫描电子显微镜图像和密度泛函理论的电势模拟表明，扭转增强的迁移率主要是由膜中的纤维组织控制。与由较大间隙分离的较少的大微晶相比，由许多较小间隙分离的较大数量的紧密堆积的扭曲纤维允许在膜表面上更好的电荷传输。
Many molecular crystals (approximately one third) grow as twisted, helicoidal ribbons from the melt, and this preponderance is even higher in restricted classes of materials, for instance, charge-transfer complexes. Previously, twisted crystallites of such complexes present an increase in carrier mobilities. Here, the effect of twisting on charge mobility is better analyzed for a monocomponent organic semiconductor, 2,5-bis(3-dodecyl-2-thienyl)-thiazolo[5,4-d]thiazole (BDT), that forms twisted crystals with varied helicoidal pitches and makes possible a correlation of twist strength with carrier mobility. Films are analyzed by X-ray scattering and Mueller matrix polarimetry to characterize the microscale organization of the polycrystalline ensembles. Carrier mobilities of organic field-effect transistors are five times higher when the crystals are grown with the smallest pitches (most twisted), compared to those with the largest pitches, along the fiber elongation direction. A tenfold increase is observed along the perpendicular direction. Simulation of electrical potential based on scanning electron microscopy images and density functional theory suggests that the twisting-enhanced mobility is mainly controlled by the fiber organization in the film. A greater number of tightly packed twisted fibers separated by numerous smaller gaps permit better charge transport over the film surface compared to fewer big crystallites separated by larger gaps.