Synthesis and field-effect transistor properties of a diseleno[3,2-: B:2′,3′- d] silole-based donor-acceptor copolymer: Investigation of chalcogen effect

We have designed and synthesized a tricyclic diseleno[3,2-b:2′,3′-d]silole (DSS) wherein the 3,3′-position of a biselenophene is bridged by a dioctylsilyl moiety. The distannylated DSS was copolymerized with a diketopyrrolopyrrole (DPP) acceptor to form a donor-acceptor copolymer PDSSDPP. The thiophene-based dithieno[3,2-b:2′,3′-d]silole (DTS) monomer and its corresponding copolymer PDTSDPP are also prepared as references for investigation of the chalcogen effect. Compared to PDTSDPP, PDSSDPP exhibits a more red-shifted absorption spectrum, a higher-lying HOMO energy level, and closer interchain packing associated with the more polarizable Se atom to induce stronger intermolecular interactions. The selenophene-based PDSSDPP shows a mobility of 2.47 × 10^-2 cm² V^-1 s^-1, which is nearly one order magnitude higher than the thiophene-based PDTSDPP with a mobility of 3.89 × 10^-3 cm² V^-1 s^-1. This result suggests that the DSS unit and its polymers are promising for OFET applications.