Interfacial Charge Transport Enhancement of Liquid-Crystalline Polymer Transistors Enabled by Ionic Polyurethane Dielectric.

In organic field-effect transistors (OFETs) using disordered organic semiconductors, interface traps that hinder efficient charge transport, stability, and device performance are inevitable. Benchmark poly(9,9-dioctylfuorene-co-bithiophene) (F8T2) liquid-crystalline polymer semiconductor has been extensively investigated for organic electronic devices due to its promising combination of charge transport and light emission properties. In this study, we demonstrated high-capacitance single-layered ionic polyurethane (PU) dielectrics enable an enhanced charge transport in F8T2 OFETs. The ionic PU dielectrics were composed of a mild blending of PU ionogel and PU solution, thereby forming a solid-state film with robust interfacial characteristics with semiconductor layer and gate electrode in OFETs and measuring high capacitance values above 10 μF cm -2 owing to the combined dipole polarization and electric double layer formation. The optimized fabricated ionic PU-gated OFETs exhibited a low-voltage operation at -3 V with a remarkable hole mobility of over 5 cm 2 V -1 s -1 (average = 2.50 ± 1.18 cm 2 V -1 s -1 ), which is the highest mobility achieved so far for liquid-crystalline F8T2 OFETs. This device also provided excellent bias-stable characteristics in ambient air, exhibiting a negligible threshold voltage shift (ΔV T ) of -0.03 V in the transfer curves after extended bias stress, with a reduced trap density. This article is protected by copyright. All rights reserved.