Urushiol Gate Dielectrics for Low-Voltage and Hysteresis-Free Organic Thin Film Transistors: Hidden Potential of Natural Polymers

Abstract

Natural polymer materials often have inimitable properties that are superior to those of artificial products. In this paper, we discuss earth-abundant and eco-friendly gate dielectric materials for organic field-effect transistors (OFETs). Urushiol, a natural conventional unsaturated hydrocarbon resin with numerous hydroxyl groups, easily forms a dense thin film that could be useful in gate dielectrics. Urushiol films were fabricated via a facile thermal curing process (100 °C, 30 min) and gave a smooth surface (Rq ∼ 0.3 nm) with a hydrophobic nature (44.6 mJ/m2). The leakage current density values remained stable at operation voltages (5 ×10–8 A/cm2 up to –3 V). Pentacene OFETs with 85 nm thick thin urushiol gate dielectrics exhibited good transfer and output characteristics with a mobility of 0.07 cm2/Vs and negligible hysteresis under only +2∼–3 V. An outstanding gate bias stability over 140 minutes under humid conditions (R.H. 80%) was achieved in the same devices. These outstanding electrical performance and stability properties were attributed to the densely packed structures of the urushiol films prepared via thermal curing. This research enables a plethora of opportunities in the field of gate dielectric materials and electronics as well as in the area of earth-abundant materials and eco-friendly products.