Molecularly Engineered Quinoxaline-Pyridyl Pyrazine Polymers for Field-Effect Transistors and Complementary Circuits

Regioregularity in conjugated polymers plays a significant role in enhancing the semiconducting properties and narrowing the optical band gap. Two donor-acceptor copolymers, specifically quinoxaline-thienylenevinylene (P1) and regioregular pyridyl pyrazine-thienylenevinylene (P2), were synthesized and characterized. Their potential applications in organic field-effect transistors (FETs) and complementary inverter circuits were explored. P2 exhibits a narrower absorption spectrum with distinct vibronic peaks compared to P1. In both top-gate and bottom-gate FET architectures, the copolymers display p-type behavior, with P2 demonstrating approximately an order of magnitude higher carrier mobility (similar to 10-3 cm2/(V s)) than P1. The performance of the FETs is further improved by the surface treatment of the source-drain contacts, which is particularly noticeable in P1. These p-type FETs, incorporating P1 and P2, were employed in complementary voltage inverter circuits along with thiazole-selenophene-linked fluorinated isoindigo (IID-TzSe) n-type organic FETs. The P1-IID-TzSe inverter, characterized by balanced p- and n-channels with similar threshold voltages, shows a gain >20 at a supply voltage of 50 V. Similar gains are also observed in the P2-IID-TzSe inverter circuits.