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Theoretical Study on the Charge Transport in Single Crystals of TCNQ, F2-TCNQ and F4-TCNQ

Abstract

2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F2-TCNQ) was recently reported that displayed excellent electron transport property in single crystal field-effect transistors (FETs). The carrier mobility can reach as high as 25 cm2 V-1 s-1 in devices. However, its counterparts TCNQ and F4-TCNQ (tetrafluoro-7,7,8,8-tetracyanoquinodimethane) didn’t exhibit the same high-efficient behavior. To better understand the significant difference in charge carrier mobility, a multiscale approach combining semiclassical Marcus hopping theory, quantum nuclear enabled hopping model and molecular dynamics simulation was performed to assess electron mobilities for the Fn-TCNQ (n=0, 2, 4) systems in this work. It is indicated that the outstanding electron transport behavior of F2-TCNQ comes from its effective 3D charge carrier percolation network due to its special packing motif and the nuclear tunneling effect. While the poor transport properties of TCNQ and F4-TCNQ stem from their invalid packing and strong thermal disorder. It is found that Marcus theory underestimates the mobilities for all the systems, while the quantum model with the nuclear tunneling effect can be able to give reasonable results compared to experiments. Moreover, the band-like transport behavior of F2-TCNQ was well described by the quantum nuclear enabled hoping 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, F2-TCNQ and F4-TCNQ crystals. A primary understanding of various noncovalent interactions response for the crystal formation is crucial for understand the structure-property relationship in organic molecular materials.

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Publication details

The article was received on 23 Oct 2017, accepted on 27 Dec 2017 and first published on 02 Jan 2018


Article type: Paper
DOI: 10.1039/C7CP07189B
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Theoretical Study on the Charge Transport in Single Crystals of TCNQ, F2-TCNQ and F4-TCNQ

    L. F. Ji, J. Fan, S. Zhang and A. Ren, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP07189B

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