Low-temperature processable and photo-crosslinkable polyimide gate dielectric for flexible thin-film transistor

A fully soluble and photo-crosslinkable gate dielectric (6 F-SPI-Cinnamoyl: 6 F-SPI-CM) was synthesized. First, hydroxyl group substituted polyimide (6 F-SPI-Hydroxyl: 6 F-SPI-OH) polymer was prepared using monomers, 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and 4,4’-(perfluoropropane-2,2-diyl)dianiline (6FHAB) through polycondensation reaction. And, then 6 F-SPI-OH was further reacted with cinnamoyl chloride to prepare a photo-crosslinkable 6 F-SPI-CM. The thin film of photo-crosslinked 6 F-SPI-CM (C-6F-SPI-CM) showed the extremely low leakage current density of <1.0 x10−11 A/cm2. In addition, 6 F-SPI-CM was easily patterned by selective UV-light exposure. A flexible pentacene thin-film transistor (TFT) on polyethersulfone (PES) substrate with photo-crosslinked 6 F-SPI-CM as a gate dielectric showed a field effect mobility of 0.11 cm2/Vs with no hysteresis behavior.