Small molecule/polymer blends prepared by environmentally-friendly process for mechanically-stable flexible organic field-effect transistors

Abstract

Abstract We fabricated flexible organic field-effect transistors (OFETs) based on a blend film composed of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) as a π-conjugated small-molecule semiconductor and poly(methylmethacrylate) (PMMA) as a polymer insulator deposited on polyethylene naphthalate (PEN) films with Al bottom-gate electrodes. The blend films were prepared by using an electrostatic spray deposition (ESD) method with environmentally-friendly (i.e., non-aromatic and halogen-free) solvents of n-butyl acetate, acetone, and hexane. The TIPS pentacene and PMMA layers were stratified separately just after the film deposition (TIPS pentacene (top) and PMMA (bottom)). The phase-separated interface with molecular-level flatness was formed with the PMMA buffer layer inserted between the blend film and Al bottom-gate electrode, which leads to superior charge transport properties. Furthermore, the flexible OFETs with a sharp phase-separated interface demonstrated superior operational stability under applied mechanical strain.