High conductivity poly(ionic liquid)-based crosslinked dielectrics

Abstract

A wide range of emerging applications, from organic electronics to batteries, require dielectrics that offer high ionic conductivity while preventing hazards associated with dielectric leakage. Poly(ionic liquids) (PILs) are a promising class of materials which combine the high ionic conductivity of ionic liquids with the desireable mechanical properties of polymers. When developing thin film devices the deposition of multiple layers may necessitate orthoganol processing, limiting the choice of processing solvents and device designs. We developed a PIL that can be crosslinked with bis(2-bromoethyl) ether (BBEE) for use as a high performing dielectric. Electrochemical impedance spectroscopy was used to establish structure–property relationships. We investigated the effect of poly(ethylene glycol) methacrylate ion conducting monomers (mPEGMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) composition in the PIL, the alkylation percentage in the PIL, and amount of BBEE to PIL on corresponding metal–insulator–metal capacitor performance. A balance between polymer composition and BBEE composition was identified to produce a robust PIL dielectric with a high electrical double layer (EDL) onset frequency and high capacitance density that is a solid at room temperature. The optimized PIL dielectric was then successfully integrated into a proof-of-concept solution-processed organic thin-film transistor (OTFT).