Abstract
Intrinsically conductive polymers free of unstable mobile dopants are highly sought after for stable and reliable electronic performance, yet remain scarce due to synthetic challenges. Here we report poly(3,4-dihydroxythiophene-alt-thiophene-3,4-dione) (HOT-DOT), a novel cross-conjugated polymer and the first polymeric analogue of a quinhydrone-like charge-transfer complex with intrinsic conductivity. HOT-DOT is synthesized through a straightforward three-step route, in which the final air oxidation step spontaneously generates a perfectly balanced 1:1 donor-acceptor architecture that promotes self-doping and stabilizes polarons. The polymer exhibits a narrow bandgap (1.38 eV), broad near-infrared absorption, and high conductivity (∼0.29 S cm(-1)), enabled by an ultrasmall π-π stacking distance (3.25 Å) despite its cross-conjugated backbone. Spectroscopic and computational analyses reveal that strong interchain donor-acceptor interactions, reinforced by ammonia coordination, stabilize the self-doped state. HOT-DOT further displays rare positive temperature coefficient (PTC) behavior and long-term ambient stability. As a proof of concept, flexible temperature sensors fabricated from HOT-DOT films show reproducible and linear thermal responses over multiple cycles. This study establishes polymeric charge-transfer complexes as a new design paradigm for intrinsically conductive, dopant-free polymers with distinctive transport and sensing properties.