Enhancement of the field-effect mobility of solution processed organic thin film transistors by surface modification of the dielectric

The electrical performance of organic thin film transistors (OTFTs) is profoundly affected by organic semiconductor crystal formation and molecular ordering. The molecular ordering induced by self-assembly mechanisms can improve carrier mobility by a few orders of magnitude. In this work, the dielectric surface was modified to obtain preferred chemical functional groups that promote semiconductor ordering on the dielectric surface. OTFTs were fabricated using heavily p-doped silicon wafers as the gate electrode and thermally grown SiO2 as the dielectric. Organosilanes, (3-mercaptopropyl)triethoxysilane and p-tolyltrimethoxysilane were used to modify the dielectric surface. Organic semiconductor, bis(triisopropylsilylethynyl) pentacene, was solution-cast as the semiconductor layer. X-ray photoelectron spectroscopy was used to characterize the modified dielectric surface. The analysis from atomic force microscopy indicated improved ordering in the semiconductor layer on silane treated dielectric surfaces. Electrical characterizations showed that the field-effect carrier mobility was enhanced by two orders of magnitude with dielectric surface modifications.