High mobility isoindigo-based π-extended conjugated polymers bearing di(thienyl)ethylene in thin-film transistors

Abstract

New isoindigo and di(thienyl)ethylene-containing π-extended conjugated polymers with different branched side-chains and molecular weights (MWs) have been synthesized. Octyldodecyl (OD) and decyltetradecyl (DT) groups were employed as side chain moieties tethered to isoindigo units. In addition, the MW of the polymer was varied by changing the polymerization time. The polymers bearing DT side chains showed much better charge transport behavior, compared to that of polymers with OD side chains. The hole mobility of high-MW PIIDDTE-III with DT side-chains was determined to be higher than that of the low-MW polymer, PIIDDTE-II with identical side-chains. The thermally annealed film of PIIDDTE-III exhibited outstanding hole mobilities of ∼2.20 cm² V⁻¹ s⁻¹ measured under ambient conditions. This work unambiguously demonstrates the effect of the branched side-chain bulkiness and MW on the thin film transistor (TFT) performances.