A Thiazole–Naphthalene Diimide Based n-Channel Donor–Acceptor Conjugated Polymer

Conjugated monomers and polymers containing 2,2′-bithiazole (BTz) and naphthalene diimide (NDI) units in the main chain were prepared. Polymer PNDI2Tz was obtained via palladium-catalyzed Stille polycondensation of a dibromo-substituted NDI derivative with distannyl-2,2′-bithiazole. The optical and electronic properties were investigated using UV–vis absorption spectroscopy and ultraviolet photoelectron spectroscopy. It was found that the polymers show very broad absorption bands in the 540 nm region, and PNDI2Tz has an optical bandgap of 1.87 eV. Computational analysis demonstrates that holes and electrons are mainly localized on the 2,2′-bithiazole and NDI units, respectively. Organic field-effect transistors (OFETs) fabricated with PNDI2Tz exhibit unipolar n-channel characteristics with mobility as high as 0.05 cm2 V–1 s–1.