Thiophene Backbone Enables Two-Dimensional Poly(arylene vinylene)s with High Charge Carrier Mobility

Linear conjugated polymers have garnered considerable interest over the past few decades. Despite the presence of intrachain π-delocalization, the impediment to their transport arises from interchain hopping interactions. In contrast, two-dimensional (2D) conjugated polymers, as represented by 2D p-conjugated covalent organic frameworks (2D c-COFs), can provide multiple conjugated strands to enhance the delocalization of charge carriers in space. Herein, we demonstrate the first example of thiophene-based 2D poly(arylene vinylene)s (PAVs, 2DPAV-BDT-BT and 2DPAV-BDT-BP, BDT= benzodithiophene, BT=bithiophene, BP=biphenyl) via Knoevenagel polycondensation. Compared with 2DPAV-BDT-BP, the fully thiophene-based 2DPAV-BDT-BT exhibits enhanced planarity and p-delocalization with a small band gap (1.62 eV) and large electronic band dispersion, as revealed by the optical absorption and density functional theory calculations. Remarkably, temperature-dependent terahertz spectroscopy discloses a unique band-like transport and outstanding room-temperature charge mobility for 2DPAV-BDT-BT (65 cm²V⁻¹s⁻¹), which far exceeds that of the linear PAVs, 2DPAV-BDT-BP, and the reported 2D c-COFs in the powder form. This work highlights the great potential of thiophene-based 2D PAVs as candidates for high-performance opto-electronics.

Reference: Yamei Liu, Heng Zhang, Hongde Yu, Zhongquan Liao, Silvia Paasch, Shunqi Xu,* Ruyan Zhao, Eike Brunner, Mischa Bonn, Hai I. Wang,* Thomas Heine, Mingchao Wang,* Yiyong Mai,* Xinliang Feng*.

Acknowledgements: L., H. Z., H. Y. contributed equally to this work. This work was financially supported by ERC grant (T2DCP, No. 819698), DFG project (CRC 1415, No. 417590517), European Union's Horizon 2020 (PROGENY, No. 899205; Graphene Flagship Core3, No. 881603; EMERGE, No. 101008701), and Center for Advancing Electronics Dresden. Y.M.L. appreciates fellowship support from the Chinese Scholarship Council (CSC). Y.M. acknowledges the financial support from National Natural Science Foundation of China (52073173 and 22225501), and National Key R&D Program of China (2021YFB4001100). We thank Dresden Center for Nanoanalysis (DCN) for the use of facilities and Matthias Kluge for TGA measurement. We appreciate Dr. Yang Lu, Dr. Yannan Liu, Albrecht Wäntig and Shaik Ghouse for helpful discussions. H.Y. and T.H. acknowledge the Alexander von Humboldt Foundation for financial support and the Centre for Information Services and High Performance Computing (ZIH) at TU Dresden for the provided computational resources. The Instrumental Analysis Center at Shanghai Jiao Tong University is also acknowledged.