High performance p-type chlorinated-benzothiadiazole-based polymer electrolyte gated organic field-effect transistors

Abstract

We report the evaluation of charge transport parameters of four p-type dichlorinated-2,1,3-benzothiadiazole (2ClBT) based conjugated polymers end-capped with different electron-donor units (thiophene (T), thieno[3,2-b]thiophene (TT), 2,2′-bithiophene (DT), and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT)) in electrolyte gated organic field-effect transistors operating at a driving voltage of −2 V. Remarkable hole mobility improvement of 0.13–0.56 cm2V−1s−1 were achieved in 2ClBTs based polymers, with P2ClBT-DT recording the highest mobility of 0.56 cm2V−1s−1 and current on/off ratio ∼107. Interestingly, a positive threshold voltage shift (ΔVTh) was observed in the transfer characteristics from the linear to saturation regime of all the 2ClBTs based polymer electrolyte gated OFET devices of L = 10 μm, contrary to devices with conventional poly(methyl methacrylate) gate dielectric, which showed a negative ΔVTh shift. Among the 2ClBTs based polymers, P2ClBT-TVT devices showed the lowest mobility and ΔVTh shift, which is attributed to severe ion diffusion in the polymer semiconducting layer owing to the vinyl group backbone susceptible to electrochemical doping. Our results emphasize essential selection consideration of the monomeric moieties, molecular ordering, π-π stacking and backbone planarity of conjugated polymers for electrolyte based organic devices.