Low temperature UV cross-linked fluorinated polyurethane for organic thin film transistors

Abstract

Organic thin film transistors (OTFTs) have attracted extensive research interest in recent years because of their light weight, low cost, and large area preparation at low temperatures, especially organic thin film transistors based on high dielectric constant (κ) organic dielectric materials with a flat surface prepared by a low-temperature solution method. Here, a UV cross-linked fluorine-containing polyurethane (PU) dielectric layer quickly curing in only 5 min at room temperature was designed and prepared by adding different contents of hexafluorobutyl acrylate through a thiolene click reaction. The spin-coated films were flat and possessed superior solvent resistance, thermal stability, and dielectric qualities. The C8-BTBT based OTFTs prepared with fluorinated PU (FPU) as the dielectric layer exhibited excellent electrical properties, with the highest mobility of 3.53 cm² V⁻¹ s⁻¹, a switching ratio of 2.8 × 10⁶, the least subthreshold swing of 0.4 V dec⁻¹, a low threshold voltage of −0.3 V, and almost no hysteresis. The results show that the comprehensive performance of FPU is obviously better than that of pure PU, so polymer fluorination is an effective method to optimize the dielectric constant and device performance. These UV cross-linked FPU dielectric materials can be applied in many applications such as flexible electronic devices in the future.