The effect of dielectric constant on device mobilities of high-performance, flexible organic field effect transistors

High-performance pentacene (μsat =6.3 cm² /V s) and poly(3-hexylthiophene) (μsat =0.43 cm² /V s) field effect transistors have been realized on flexible substrate with low operating voltage (<-5 V), utilizing a trilayer sol-gel silica gate dielectric. Furthermore, the permittivity of the dielectric was tuned from ∼7 to ∼10 by varying plasma treatments, allowing the study of charge carrier mobility variation with k. A 65% reduction in the saturation mobility of the devices was observed when k increases, suggesting that the energetic disorder at the interface between the active layer and the dielectric can be modulated by the high polarizability of the bulk dielectric.