| Summary: | Abstract An open‐shell quinoidal conjugated polymer exhibiting n‐type semiconducting behavior is successfully synthesized and characterized. An electron‐deficient azaaromatic unit is proven to reduce the energy levels of frontier orbitals via the electronegative nitrogen atom and steric hindrance within the polymer backbone. A synthesized azaquinoidal bithiophene (azaQuBT) is a quinoidal bithiophene that is end‐functionalized with a pyridine ring. The open‐shell quinodial conjugated polymer, poly(azaquinoidal bithiophene‐thiophene), PazaQuBT‐T, is synthesized using azaQuBT and thiophene. The extended quinoidal building block, which has an open‐shell diradical character, induces low bandgaps, redox amphoterism, and high‐spin‐induced paramagnetic behavior of the resulting polymer. PazaQuBT‐T achieves ambipolar charge‐transport behavior in organic field‐effect transistor (OFET) devices. Through a PEIE treatment onto the contact electrode, PazaQuBT‐based OFETs exhibit unipolar n‐channel operation with electron mobility up to 0.98 cm2 V−1 s−1. This work demonstrates the development of novel open‐shell conjugated polymers with high‐spin characteristics and n‐type semiconducting property.
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