Fabrication of flexible organic thin-film transistors based on negative acting photosensitive novolak polymer as an organic gate insulator

Abstract

ABSTRACTA diazonaphthoquinone (DNQ)-based cross-linkable photo-sensitive cresol novolak resin through acid-catalyzed condensation with melamine molecules is presented as an organic gate insulator (OGI) for the fabrication of poly(3-hexylthiophene) thin-film transistors. This novolak OGI exhibits a remarkably smooth surface of Ra 1.0 nm and RMS 0.3 nm and shows excellent chemical resistance against common process solvents upon a post exposure bake ≥150°C. The corresponding metal-insulator-metal diode incorporated with a 200 nm thick OGI demonstrates remarkable low leakage current level of 10 pA/cm2 @3 MV/cm. Bottom-contact poly(3-hexylthiophene) (P3HT) transistors with novolak OGI on both rigid glass and flexible polyethylene terephthalate (PET) plastic substrates are further demonstrated, suggesting that novolak polymer is a promising candidate for realizing a high performance OGI at low processing temperature.