Effect of surface-modified polyimide gate insulator through hybridization on the performance of organic thin-film transistors

Abstract

Surface modification of the gate insulator is a key to performance improvement of organic thin-film transistors (OTFTs). To date, the surface modification of a gate insulator is based on a primer or buffer layer deposition on top of a gate insulator. We report an approach to modify the surface of a gate insulator without a primer and/or buffer layer deposition. In order to obtain polymer gate insulators with well-controlled surface properties, a hybridization method was used and some gate insulators were prepared by varying the hybridization ratio of polyimide with a nonpolar octadecyl side chain to poly(amic acid). The surface property of the hybrid gate insulator varies according to the hybridization ratio. We believe that the long alkyl side chain of the hybrids protrudes from the surface, and makes the surface more hydrophobic. The modified hydrophobic surface strongly affects an initial growth mechanism of pentacene and subsequently the performance of OTFTs. The performance of pentacene OTFTs with the hybrids is superior to that of the OTFTs with only poly(amic acid) and exhibited a carrier mobility of 0.94cm2∕Vs, an on/off current ratio of around 106, and a subthreshold slope of 3.1V∕dec.