Multifunctional Flexible Organic Transistors with a High-<i>k</i>/Natural Protein Bilayer Gate Dielectric for Circuit and Sensing Applications

Abstract

Organic field-effect transistors (OFETs) have opened up new possibilities as key elements for skinlike intelligent systems, due to the capability of possessing multiple functionalities. Here, multifunctional OFET devices based on gelatin, a natural biopolymer gate dielectric, and TIPS-pentacene as an organic semiconductor are extensively explored. Gelatin is combined with a thin high-k HfO2 dielectric layer deposited by atomic layer deposition (ALD) to achieve a low leakage current and low-voltage operation. The natural biopolymer offers a better semiconductor:dielectric interface, leading to better charge conduction in the devices, along with an enhancement of sensing capabilities giving additional functionality. These fabricated flexible OFET devices exhibit excellent electrical characteristics with a high field-effect mobility reaching over 2 cm2/(V s) (extracted with Ci at 1 kHz), a low subthreshold swing (SS) of ∼200 mV/dec, and a high current on–off (Ion/Ioff) ratio at a low operating voltage of −5 V with excellent electrical and mechanical stability. Moreover, circuit and multiparameter sensing capabilities for visible and UV light, as well as for humidity and breath rate, have been successfully demonstrated for these devices. Our results indicate that these multifunctional OFET devices can open up a plethora of opportunities for practical applications such as real-time health and environmental monitoring.