Synthesis and characterization of naphthalenediimide-thienothiophene-conjugated polymers for OFET and OPT applications

Three novel donor-acceptor-based conjugated polymers with a naphthalenedimide-thienothiophene backbone, possessing electron acceptor nitrile (CN) and electron donor methoxy (OMe) groups and an acetylene spacer were designed and synthesized. They were successfully obtained via Stille and Sonogashira couplings and were characterized using UV-Vis spectrometry, cyclic voltammetry and DFT studies. They were used to fabricate organic field-effect transistors (OFETs) and organic phototransistors (OPTs) devices. 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 the CN moiety showed the highest photosensitivity P value (209), the copolymer containing the acetylene spacer and electron donor methoxy group exhibited the largest photoresponsivity R-value (2.2 × 10⁶ A W⁻¹). Our findings demonstrated that the 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.