Ji Li-Fei, Fan Jian-Xun, Zhang Shou-Feng, Ren Ai-Min
Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China.
Phys Chem Chem Phys. 2018 Jan 31;20(5):3784-3794. doi: 10.1039/c7cp07189b.
2,5-Difluoro-7,7,8,8-tetracyanoquinodimethane (F-TCNQ) was recently reported to display excellent electron transport properties in single crystal field-effect transistors (FETs). Its carrier mobility can reach 25 cm V s in devices. However, its counterparts TCNQ and F-TCNQ (tetrafluoro-7,7,8,8-tetracyanoquinodimethane) do not exhibit the same highly efficient behavior. To better understand this significant difference in charge carrier mobility, a multiscale approach combining semiclassical Marcus hopping theory, a quantum nuclear enabled hopping model and molecular dynamics simulations was performed to assess the electron mobilities of the F-TCNQ (n = 0, 2, 4) systems in this work. The results indicated that the outstanding electron transport behavior of F-TCNQ arises from its effective 3D charge carrier percolation network due to its special packing motif and the nuclear tunneling effect. Moreover, the poor transport properties of TCNQ and F-TCNQ stem from their invalid packing and strong thermal disorder. It was found that Marcus theory underestimated the mobilities for all the systems, while the quantum model with the nuclear tunneling effect provided reasonable results compared to experiments. Moreover, the band-like transport behavior of F-TCNQ was well described by the quantum nuclear enabled hopping model. In addition, quantum theory of atoms in molecules (QTAIM) analysis and symmetry-adapted perturbation theory (SAPT) were used to characterize the intermolecular interactions in TCNQ, F-TCNQ and F-TCNQ crystals. A primary understanding of various noncovalent interaction responses for crystal formation is crucial to understand the structure-property relationships in organic molecular materials.
2,5-二氟-7,7,8,8-四氰基对苯二醌二甲烷（F-TCNQ）最近被报道在单晶场效应晶体管（FET）中表现出优异的电子传输特性。在器件中其载流子迁移率可达25 cm² V⁻¹ s⁻¹。然而，其同类物TCNQ和F-TCNQ（四氟-7,7,8,8-四氰基对苯二醌二甲烷）却没有表现出同样高效的行为。为了更好地理解电荷载流子迁移率的这一显著差异，本文采用了一种多尺度方法，结合半经典马库斯跳跃理论、量子核促进跳跃模型和分子动力学模拟来评估F-TCNQ（n = 0, 2, 4）体系的电子迁移率。结果表明，F-TCNQ出色的电子传输行为源于其特殊堆积模式导致的有效的三维电荷载流子渗流网络以及核隧穿效应。此外，TCNQ和F-TCNQ较差的传输特性源于它们无效的堆积和强烈的热无序。研究发现，马库斯理论低估了所有体系的迁移率，而考虑核隧穿效应的量子模型与实验相比给出了合理的结果。此外，量子核促进跳跃模型很好地描述了F-TCNQ的带状传输行为。另外，利用分子中的原子量子理论（QTAIM）分析和对称适配微扰理论（SAPT）来表征TCNQ、F-TCNQ和F-TCNQ晶体中的分子间相互作用。对晶体形成过程中各种非共价相互作用响应的初步理解对于理解有机分子材料的结构-性能关系至关重要。
