Enhanced stability of poly(3-hexylthiophene) transistors with optimally cured poly(methyl methacrylate) dielectric layers

Poly(3-hexylthiophene)-based organic field-effect transistors (OFETs) have been fabricated on poly(methyl methacrylate) (PMMA) gate dielectric layers under different process conditions, resulting in very different device stability in ambient air. The dielectric layers were prepared by spin coating and subsequently curing at various temperatures (120, 150, and 180 °C) or by ultraviolet light (UV) exposure. With respect to the variations of the on/off current ratio and the threshold voltage, dramatically enhanced stability of the OFETs with the PMMA layer cured at 150 °C has been demonstrated when compared to those cured at different temperatures. The devices cured by UV exposure showed even more superior stability, with reliable performance in ambient air for more than 10 days. The differences in the film surface morphology were analyzed and possible mechanisms for the enhanced stability are discussed.