Synthesis and Characterization of Naphthalenediimide-Thienothiophene Conjugated Polymers for OFET and OPT Applications

Three novel donor-acceptor-based conjugated polymers with naphthalenedimide-thienothiophene backbone, possessing electron acceptor nitrile (CN) and electron donor methoxy (OMe) groups and acetylene spacer were designed and synthesized. They were successfully obtained via Stille and Sonogashira couplings and characterized using UV-Vis spectrometry, cyclic voltammetry and DFT studies. Their devices of organic field-effect transistors (OFETs) and organic phototransistors (OPTs) were fabricated. All the polymers exhibited n-type behavior in bottom-gate and top-contact organic thin-film transistors. Regarding the OPT devices, while the polymer with CN moiety showed the highest photosensitivity P value (209), the copolymer containing acetylene spacer and electron donor methoxy group exhibited the largest photoresponsivity R value (2.2 x 10⁶ A/W). Our findings demonstrated that introduction of various functional groups and a triple bond spacer is an effective approach for manipulating the optical and electronic properties as well as enhancing the overall performance of the devices.