N-type organic field-effect transistor using polymeric blend gate insulator with controlled surface properties

Fabrication of n-type organic thin-film transistors (OTFTs) based on organic semiconductor and organic gate insulator is essential for the achievement of organic complementary logic circuit. This article deals with n-type OTFTs with copper hexadecafluorophthalocyanine (F16CuPc) and polymeric blend as an active semiconductor and a gate insulator, respectively. The gate insulator was prepared by blending poly(amic acid) and soluble polyimide with long alkyl side chains (C-18 group), which make the surface of the gate insulator more hydrophobic. In order to reduce properties mismatch at interface between F16CuPc and the gate insulator, surface tension of the gate insulator was controlled to 39.1 dyn/cm, which is similar to that of F16CuPc (36.9 dyn/cm). AFM and X-ray diffraction measurements indicated that F16CuPc deposited on the gate insulator showed worm-like flat lying crystal and was highly ordered with a peak of 6.12 degrees. The F16CuPc OTFTs with the gate insulator function as n-channel accumulation mode and their performance was better than that of F16CuPc OTFTs with SiO2, demonstrating its potential applications for flexible organic display. Charge carrier field-effect mobility, I-ON/I-OFF, and subthreshold slope of the OTFT were 6 x 10(-3) cm(2)/V s, 5.4 x 10(3), and 7.3 V/dec, respectively. (C) 2005 Elsevier B.V. All rights reserved.