Highly Planar and Completely Insulated Oligothiophenes: Effects of π-Conjugation on Hopping Charge Transport
Highly Planar and Completely Insulated Oligothiophenes: Effects of π-Conjugation on Hopping Charge Transport
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DOI：
10.1021/acs.jpclett.9b00747
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发表时间：
2019-06-20
影响因子：
5.7
通讯作者：
Aso, Yoshio
中科院分区：
文献类型：
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作者：
Ie, Yutaka;Okamoto, Yuji;Aso, Yoshio
阐明π共轭分子中远距离电荷输运的性质对有机电子材料的发展具有重要意义。然而，由于缺乏不同共轭度和数纳米长度的π共轭骨架，迄今为止还没有实验研究π共轭度对跳跃电荷输运的影响。在这里，我们开发了高度平面和完全绝缘的低硫噻吩，长度在0.85到9.64 nm之间。与扭曲的寡硫噻吩相比，平面分子的单分子电导测量结果显示：(1)在跳跃输运体系中具有较小的活化能和较大的电导；(2)在隧穿和跳跃传导之间的交叉向短分子长度转移。理论计算表明，平面骨架产生的小重组能和窄能隙导致了这些优越的特性。研究表明，π共轭的平面性对跳电荷输运具有显著的优势。
Elucidating the nature of long-range intramolecular charge transport in pi-conjugated molecules is of great importance for the development of organic electronic materials. However, the effects of the degree of pi-conjugation on the hopping charge transport have not been experimentally explored so far owing to the lack of pi-conjugated backbones with different conjugation degrees and several-nanometer lengths. Here we develop highly planar and completely insulated oligothiophenes between 0.85 and 9.64 nm in length. As compared to distorted oligothiophenes, single-molecule conductance measurements of the planar molecules show (i) a smaller activation energy and larger electrical conductance in the hopping transport regime and (ii) a shift in crossover between tunneling and hopping conduction toward a short molecular length. Theoretical calculations indicate that small reorganization energies and narrow energy gaps derived from the planar backbones result in these superior characteristics. This study reveals that the planarity of pi-conjugation has significant advantages for hopping charge transport.