An n‐Type Open‐Shell Conjugated Polymer with High‐Spin Ground‐State and High Intrinsic Electrical Conductivity

Abstract

Open‐shell conjugated polymers with a high intrinsic conductivity and high‐spin ground state hold considerable promise for applications in organic electronics and spintronics. Herein, two novel acceptor‐acceptor (A‐A) conjugated polymers based on a highly electron‐deficient quinoidal benzodifurandione unit have been developed, namely DPP‐BFDO‐Th and DPP‐BFDO. The incorporation of the quinoidal moiety into the polymers backbones enables deeply aligned lower‐lying lowest unoccupied molecular orbital (LUMO) levels of below −4.0 eV. Notably, DPP‐BFDO exhibits an exceptionally low LUMO (−4.63 eV) and a high‐spin ground state characterized by strong diradical characters. Moreover, a self‐doping through intermolecular charge‐transfer is observed for DPP‐BFDO, as evidenced by X‐ray photoelectron spectroscopy (XPS) studies. The high carrier concentration in combination with a planar and linear conjugated backbone yields a remarkable electrical conductivity (σ) of 1.04 S cm−1 in the “undoped” native form, ranking among the highest values reported for n‐type radical‐based conjugated polymers. When employed as an n‐type thermoelectric material, DPP‐BFDO achieves a power factor of 12.59 μW m−1 K−2. Furthermore, upon n‐doping, the σ could be improved to 65.68 S cm‐1. This study underscores the great potential of electron‐deficient quinoidal units in constructing dopant‐free n‐type conductive polymers with a high‐spin ground state and exceptional intrinsic conductivity.