Band-Like Electron Transport with Record-High Mobility in the TCNQ Family
Band-Like Electron Transport with Record-High Mobility in the TCNQ Family
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DOI：
10.1002/adma.201405699
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发表时间：
2015-04-17
影响因子：
29.4
通讯作者：
Morpurgo, Alberto F.
中科院分区：
文献类型：
--
作者：
Krupskaya, Yulia;Gibertini, Marco;Morpurgo, Alberto F.
在高质量的有机单晶场效应晶体管中，电子传输发生在类带区，载流子迁移率随着温度的降低而增加。目前尚不清楚这种现象的微观性质，也不清楚为什么它只发生在少数材料中。在这里，需要对具有高质量可复制输运特性的密切相关材料进行比较研究。我们研究了不同TCNQ（四氰喹诺二甲烷）分子在单晶中的电子传递，并结合能带结构计算。我们发现F2-TCNQ器件在冷却后具有非常高的电子迁移率和前所未有的迁移率增加，而在TCNQ和F4-TCNQ中，迁移率明显较低，并且在冷却后降低。我们分析了这些材料的晶体和电子结构，发现F2-TCNQ晶体确实是实现优异输运性能的理想晶体。我们的分析还表明，要了解三种材料之间的差异，仅研究它们的能带结构是不够的，还需要研究电子-声子耦合。除了F2-TCNQ出色的输运性质外，我们工作的一个关键结果是确定了Fx-TCNQ家族，作为研究有机晶体中电子输运最基本方面的范例。
In highest quality organic single-crystal field-effect transistors, electron transport occurs in the band-like regime, with the carrier mobility increasing upon lowering temperature. Neither the microscopic nature of this regime, nor why it occurs only in a small number of materials is currently understood. Here, comparative studies of closely related materials, exhibiting high-quality reproducible transport properties are needed. We performed a study of electron transport in single-crystals of different TCNQ (tetracyanoquinodimethane) molecules, combined with band structure calculations. We show that F2-TCNQ devices exhibit very high electron mobility and an unprecedented increase in mobility upon cooling, whereas in TCNQ and F4-TCNQ the mobility is substantially lower and decreases upon cooling. We analyze the crystal and electronic structures of these materials and find that F2-TCNQ crystals are indeed ideal to achieve outstanding transport properties. Our analysis also shows that to understand the difference between the three materials, studying their band structure is not sufficient, and that the electron-phonon coupling needs to be investigated as well. Besides the outstanding transport properties of F2-TCNQ, a key result of our work is the identification of the Fx-TCNQ family as a paradigm to investigate the most fundamental aspects of electronic transport in organic crystals.