Facile and reliable route to ensure chemical-environmental stability of pen-printed organic transistors with blended polymer Semiconductor–Insulator

Abstract

We have introduced an efficient pen-printing method for solution-process fabrication of organic field-effect transistors (OFETs). Although polymer semiconductors used in this method are promising materials that provide electrical properties with mechanical flexibility, they have drawbacks such as poor long-term driving stability or dramatically decreased electrical performance under chemical environments. Herein we applied the spontaneous phase separation in blended polymers of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and polystyrene (PS) as model semiconducting and protective polymers, respectively. A protective PS layer spontaneously formed on top of the PTAA layer, preventing direct exposure to chemical molecules and thus greatly improving long-term driving stability under ambient, high-humidity, and even ethanol vapor conditions. Even under the harshest ethanol vapor condition, the average field-effect mobility (μFET) of the PTAA + PS-blend FETs were maintained at 76% or more, and the threshold voltage showed only a small change of ±1.1 V over the range of vacuum, ambient, 75% humidity, and ethanol vapor conditions. Furthermore, μFETs of the PTAA + PS-blend FETs showed a low range of variation of about ±10% during 50 repeated measurements over 100 min under all conditions. The result suggests an efficient way forming a protective layer without an additional deposition step to secure the chemical and environmental stabilities of practical electronics.