Cyanoethyl cellulose-based nanocomposite dielectric for low-voltage, solution-processed organic field-effect transistors (OFETs)

Low voltage organic field-effect transistors (OFETs) using solution-processed cyanoethyl cellulose (CEC) and CEC-based nanocomposites as the gate dielectric are demonstrated. Barium strontium titanate (BST) nanoparticles are homogeneously dispersed in CEC to form the high-k (18.0 ± 0.2 at 1 kHz) nanocomposite insulator layer. The optimised p-channel DPPTTT OFETs with BST-CEC nanocomposite as the gate dielectric operate with minimal hysteresis, display field-effect mobilities in excess of 1 cm² V^-1 s^-1 at 3 V, possess low subthreshold swings (132 ± 8 mV dec^-1), and have on/off ratios greater than 10³. Addition of a 40-50 nm layer of cross-linked poly(vinyl phenol) (PVP) on the surface of the nanocomposite layer significantly decreases the gate leakage current (<10^-7 A cm^-2 at ±3 V) and the threshold voltage (< -0.7 V) enabling operation of the OFETs at 1.5 V. The presented bilayer BST-CEC/PVP dielectrics are a promising alternative for the fabrication of low voltage, solution-processed OFETs that are suitable for use in low power, portable electronics.