Synthesis, characterization, and field-effect transistor performance of naphtho[1,2-b:5,6-b′]dithiophene-based donor–acceptor copolymers

Three donor–acceptor (D–A) copolymers, PzNDT-T-DPP, PzNDT-F-DPP and PzNDTTPD, using 4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b′]dithiophene (zNDT) as an electron-rich unit and diketopyrrolopyrrole (DPP) or thieno[3,4-c]pyrrole-4,6-dione (TPD) as an electron-deficient one, were designed and synthesized via a Pd-catalyzed Stille-coupling method. All copolymers possess good solubility, high thermal stability, as well as good film-forming ability. Optical and electrochemical characterization of thin films of these polymers reveals band gaps in the range of 1.29–2.04 eV. These polymers exhibit excellent hole mobility when used as the active layer in organic field-effect transistors (OFETs) devices. Among the series, the highest hole mobility of 0.11 cm2 V−1 s−1 is achieved in bottom gate and top-contact OFET devices based on PzNDT-F-DPP. This work demonstrates that zNDT is a promising unit to build D–A copolymers for organic semiconductors with good performance.