Synthesis and FET Characterization of Novel Ambipolar and Low-Bandgap Naphthalene-Diimide-Based Semiconducting Polymers

A novel series of naphthalene-diimide-based semiconducting polymers (P1-P4) containing benzodithiophene or dithienopyrrole were successfully synthesized for ambipolar semiconducting materials showing near infrared absorptions. The incorporation of a 3-hexylthiophene (3HT) spacer extended the intramolecular charge-transfer (ICT) peak from lambda(onset) = 739 nm (P1) to 785 nm (P3). Moreover, about 250 nm red-shift of the ICT peaks was observed in P2 and P4 compared to P1 and P3 due to the increased high-lying HOMO energy levels. The grazing incidence X-ray scattering of the P3 and P4 films proved the slightly improved crystalline order in the pi-pi stacking direction, indicating that the planar backbone is probably due to the introduced 3HT. The P1-P4-based field-effect transistor showed n-type dominant ambipolar characteristics. The P2 and P4 showed higher electron mobilities up to 1.5 x 10(-2) cm(2) V-1 s(-1) than P1 and P3, which might be influenced by the orientation of the polymer backbone and the intermolecular orbital overlap. (C) 2015 Wiley Periodicals, Inc.