A Stable and Polar Triplet-Ground-State Conjugated Polymer With High Intrinsic Electrical Conductivity

Developing molecular materials with high intrinsic n-type electrical conductivity (σ) independent of extrinsic doping remains a formidable challenge in organic electronics. Herein, we report a novel acceptor-acceptor type open-shell conjugated polymer (OSCP), PBBT-gDPP, featuring a proquinoidal benzobis(1,2,5-thiadiazole) (BBT)-based backbone and polar oligo(ethylene glycol) side chains. In-depth spectroscopic, electrochemical, and magnetic characterizations uncover that this acceptor-acceptor architecture, benefiting from its planar backbone and multiple proquinoidal units, yields an ultra-narrow bandgap (E_g < 0.6 eV), an open-shell triplet ground state (S = 1), and significant diradicaloid character. These features, complemented by polar side chains that modulate the local dielectric environment to assist in polaron transport, result in a high intrinsic σ of 9.21 S cm^-1 with substantial ambient stability and a power factor of 6.49 µW m^-1 K^-2 when PBBT-gDPP is applied as an n-type single-component organic thermoelectric material. The conductivity surpasses those of previously reported undoped conjugated materials. Notably, the near-amorphous morphology, characterized by a high paracrystalline disorder parameter of ∼23%, imparts exceptional mechanical robustness, retaining 80% of its initial σs after 3000 bending cycles. This work underscores the significant potential of polar high-spin OSCPs for next-generation, dopant-free, and flexible organic electronics.