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

ABSTRACT

A 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.

KEYWORDS:

• Novolak
• organic gate insulator
• organic thin-film transistors

Additional information

Funding

The work is supported by National Natural Science Foundation of China (Grant No.61574092, 61604028), the Science and Technology Research Program of Chongqing Municipal Education Commission (Grant No.KJ1704077, KJ1600432) and Research Fund for the Doctoral Program of Chongqing University of Posts and Telecommunications (Grant No.A2016-98). It was performed in part at the facilities in National Engineering Lab for TFT-LCD Key Materials and Technologies in SJTU.