Flexography Printing for Organic Thin Film Transistors

Abstract

High throughput manufacture is of key importance for flexible electronics based on functional organic thin films. One challenge in particular is patterning at high speeds. In this paper results are presented of in-vacuum patterning of an organic dielectric, which has been used in organic thin film transistors. This combines an industry standard patterning method with resolution good enough to create functional devices. The viability of flexography is critiqued from the literature and the compatibility of the diacrylate dielectric monomer with printing system is investigated. It is found that flexography printing of a diacrylate monomer is viable and compatible and initial results from print trials are described. The results show that good pattern fidelity can be achieved with capacitance measured to be between 11 and 13nF.cm-2 with a thickness of 40nm, but that the curing step of the process leads to high surface roughness, although without pin hole defects. The surprisingly thin acrylate layers are attributed to the low viscosity of the monomer and the high capacitance measured being a result of the large surface area of the rough acrylate surface, probably resulting from the charged particle curing step. This paper concludes that this in-vacuum patterning technique could have many applications for organic electronic devices.