Thiadizoloquinoxaline-Based Low-Bandgap Conjugated Polymers as Ambipolar Semiconductors for Organic Field Effect Transistors

Two novel conjugated polymers with high molecular weight, PBDTTQ-3 and PAPhTQ, were synthesized by tuning alkyl chains and alternating the electron-donating ability of the thiadiazoloquinoxaline (TQ) moiety. Both polymers have excellent solubility in common organic solvents. UV–vis–NIR absorption and cyclic voltammetry indicate a bandgap of (0.76 eV) and high electron affinity level (−4.08 eV) for PBDTTQ-3 . Two dimensional wide-angle X-ray scattering shows that both polymers are only poorly ordered in the bulk but possess a close π-stacking distance of 0.36 nm. Despite the disorder in thin film observed by grazing incidence wide-angle X-ray scattering, PBDTTQ-3 exhibits good ambipolar transport, with a maximum hole mobility of 0.22 cm 2 V –1 s –1 and comparable electron mobility of 0.21 cm 2 V –1 s –1 .