Semiconducting Conjugated Coordination Polymer with High Charge Mobility Enabled by “4 + 2” Phenyl Ligands
Xing Huang, Shuai Fu, Cong Lin, Lu Yang, Mingchao Wang, Peng Zhang, Chuanhui Huang, Zichao Li, Zhongquan Liao, Ye Zou, Jian Li, Shengqiang Zhou, M. Helm, Petko St. Petkov, Thomas Heine, Mischa Bonn, Hai I. Wang, Xinliang Feng, Renhao Dong⧫
Abstract
Electrically conductive coordination polymers and metal–organic frameworks are attractive emerging electroactive materials for (opto-)electronics. However, developing semiconducting coordination polymers with high charge carrier mobility for devices remains a major challenge, urgently requiring the rational design of ligands and topological networks with desired electronic structures. Herein, we demonstrate a strategy for synthesizing high-mobility semiconducting conjugated coordination polymers (c-CPs) utilizing novel conjugated ligands with D 2 h symmetry, namely, “4 + 2” phenyl ligands. Compared with the conventional phenyl ligands with C 6 h symmetry, the reduced symmetry of the “4 + 2” ligands leads to anisotropic coordination in the formation of c-CPs. Consequently, we successfully achieve a single-crystalline three-dimensional (3D) c-CP Cu 4 DHTTB (DHTTB = 2,5-dihydroxy-1,3,4,6-tetrathiolbenzene), containing orthogonal ribbon-like π– d conjugated chains rather than 2D conjugated layers. DFT calculation suggests that the resulting Cu 4 DHTTB exhibits a small band gap (∼0.2 eV), strongly dispersive energy bands near the Fermi level with a low electron-hole reduced effective mass (∼0.2 m 0 * ). Furthermore, the four-probe method reveals a semiconducting behavior with a decent conductivity of 0.2 S/cm. Thermopower measurement suggests that it is a p-type semiconductor. Ultrafast terahertz photoconductivity measurements confirm Cu 4 DHTTB’s semiconducting nature and demonstrate the Drude-type transport with high charge carrier mobilities up to 88 ± 15 cm 2 V –1 s –1, outperforming the conductive 3D coordination polymers reported till date. This molecular design strategy for constructing high-mobility semiconducting c-CPs lays the foundation for achieving high-performance c-CP-based (opto-)electronics.