Low-temperature processable inherently photosensitive polyimide as a gate insulator for organic thin-film transistors

We have fabricated organic thin-film transistors (OTFTs) on polyethersulfone substrate using low-temperature processable, inherently photosensitive polyimide as the gate insulator and pentacene as the active material. The polyimide was prepared through two-step reaction. The polyimide precursor, poly(amic acid), was prepared from a dianhydride and aromatic diamine through a polycondensation reaction, and subsequently converted to its corresponding polyimide by a chemical imidization. Photolithographic properties of the polyimide are investigated. The pattern resolution of the cured polyimide was about $50\mu \mathrm{m}$ . The pentacene OTFTs with the patterned polyimide were obtained with a carrier mobility of $0.1{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ and $I_{\text{ON}}∕I_{\text{OFF}}$ of $5\times {10}^5$ . The OTFT characteristics are discussed in more detail with respect to the electrical properties of the photosensitive polyimide thin film. This low-temperature photopatternable polyimide paves the way for the easy and low-cost fabrication of OTFT arrays without expensive and complicated photolithography and dry etching processes.