Polymer bilayer films with semi-interpenetrating semiconducting/insulating microstructure for field-effect transistor applications

Abstract

We report an unexpected improvement in the microstructural and electrical properties of regioregular poly(3-hexylthiophene) (P3HT) as an active layer in field-effect transistors (FETs) by introducing soft insulating chains from poly(methyl methacrylate) (PMMA) as a cover layer in a solvent mode-dependent manner. A joint experimental and theoretical spectroscopic and electrical analysis is provided to study the P3HT/PMMA bilayer films with semi-interpenetrating semiconducting/insulating interlocked interdiffusion microstructures. Absorption and Raman studies reveal that disordered P3HT chains in films cast from a low-boiling point (bp) solvent favor reorganization into more ordered structures during PMMA covering, thus enhancing the electrical and switch behaviors of FETs. Although high-bp solvents initially create highly crystalline P3HT films, the films are significantly destroyed after the deposition of the PMMA layer, thus dramatically degrading FET characteristics. The semi-interpenetrating semiconducting/insulating microstructures in the designed bilayer films indicate the possibility of ameliorating field-effects in polymer FETs, especially in subthreshold swing and switch on–off behaviors.