Cross-linked poly(hydroxy imide) gate-insulating materials for low-temperature processing of organic thin-film transistors

A polymeric insulating material cured at the low temperature of 130 degrees C through the thermal cross-linking reaction of poly(hydroxy imide) (PHI) and 2,2-bis(4-(2-(vinyloxy)ethoxy)phenyl)propane (BPA-DEVE) was characterized to determine its applicability in organic thin-film transistors (OTFTs) on plastic substrates. Thin films of cross-linked PHI showed smooth surfaces and exhibited high breakdown voltages exceeding 3 MV cm(-1) and low dependences of capacitance on frequency. Pentacene and polymer semiconductor-based TFTs were fabricated employing this gate insulator on polyethylene naphthalate substrates. The pentacene-based TFT achieved the mobility of 0.13 cm(2) V-1 s(-1) without hysteresis, and TFTs fabricated by the solution processing of the polymer semiconductor also exhibited negligible hysteresis and gate leakage currents below 0.1 nA. These electrically stable characteristics can be attributed to the formation of intramolecular hydrogen bonds in PHI which impeded the effect of moisture-induced slow polarization.