A two-dimensional cross-linked polythiophene network

Abstract

Solution-processed polythiophene thin films suffer from low efficient inter-molecular carrier hopping and undermined conjugation arising from chain twist and random entanglement. Forming a graphene like two-dimensional (2D) cross-linked conjugated polymer network is one of the promising strategies to solve this problem. Here, we synthesize a decimeter-sized 2D cross-linked polythiophene network (2DPT) via surface-confined Ullmann coupling, with a thickness of 1.3 nm and a transmittance of ∼97% at 550 nm. The 2D cross-linked network improves charge carrier transport, resulting in a carrier mobility up to 4.6 cm² V⁻¹ s⁻¹ and conductance of 206 S cm⁻¹, much higher than that of normal solution-processed conjugated polymer films. Owing to the efficient carrier transport, atomic thickness and large conjugated surface, this new conjugated polymer exhibits a fast response to stimuli as the channel in a liquid-gated H₂O₂ sensor, and low contact resistance as bottom-contact electrodes in organic field-effect transistors with high carrier mobility.