Synthesis and application of dual electron-deficient featured copolymers and their sequential fluorination for ambipolar organic thin film transistors

Abstract

Benzodithiophenedione (BDD) and benzothiadiazole (BT) are strong electron-accepting moieties that are extensively utilized in electronic devices because of their high π-stacking capability and improved charge carrier mobilities. In this study, we employed a dual acceptor–acceptor (A–A) strategy to develop three low-band-gap, thermally stable conjugated polymers (BDD-BT, BDD-FBT, and BDD-2FBT) featuring BDD and BT and studied their physiochemical and transfer properties. Furthermore, the successful addition of thio (S)-functionalized flexible chains to BDD and the fluorine (F) atom on BT resulted in tunable optical and electrochemical properties. Computational calculations indicate that the collective effect of S and F atoms on the outer side of BDD-BT-based polymers efficiently lowered the energy levels and increased the backbone planarity. Top-gate bottom-contact (TGBC) organic field-effect transistor (OTFT) devices fabricated with BDD-BT-based polymers exhibit a typical bipolar charge transport behavior. The best OFET devices fabricated with polymer BDD-BT exhibited balanced hole and electron mobilities of up to 0.513 cm² v⁻¹ s⁻¹ and 0.577 cm² v⁻¹ s⁻¹, respectively.