Structure‐Independent Conductance of Thiophene‐Based Single‐Stacking Junctions

• Published in: Angewandte Chemie International Edition 2020-02, Vol.59 (8), p.3280-3286
• Main Authors: Li, Xiaohui, Wu, Qingqing, Bai, Jie, Hou, Songjun, Jiang, Wenlin, Tang, Chun, Song, Hang, Huang, Xiaojuan, Zheng, Jueting, Yang, Yang, Liu, Junyang, Hu, Yong, Shi, Jia, Liu, Zitong, Lambert, Colin J., Zhang, Deqing, Hong, Wenjing
• Format: Article
• Language: English
• Subjects: Charge transport; Conductance; conducting materials; Conjugation; intermolecular charge transport; mechanically controllable break junctions; Molecular structure; Resistance; Stacking; thiophene junctions
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201913344

The experimental investigation of intermolecular charge transport in π‐conjugated materials is challenging. Herein, we describe the investigation of charge transport through intermolecular and intramolecular paths in single‐molecule and single‐stacking thiophene junctions by the mechanically controllable break junction (MCBJ) technique. We found that the ability for intermolecular charge transport through different single‐stacking junctions was approximately independent of the molecular structure, which contrasts with the strong length dependence of conductance in single‐molecule junctions with the same building blocks, and the dominant charge‐transport path of molecules with two anchors transited from an intramolecular to an intermolecular path when the degree of conjugation increased. An increase in conjugation further led to higher binding probability owing to the variation in binding energies, as supported by DFT calculations. Which mode of transport? The conductance of thiophene‐based single‐stacking junctions was found to be nearly independent of the conjugation pattern of the molecular structure. When the length of the conjugated region increased, there was a change in the dominant charge‐transport path from intramolecular to intermolecular (see picture).