Low-Voltage pH Sensor Tag Based on All Solution Processed Organic Field-Effect Transistor

By reducing the sub-gap density of states at the channel, an all solution processed low-voltage organic field-effect transistor (OFET) was realized on a micrometer-thick SU8 gate dielectric layer. The device exhibits excellent operational stability under continuous bias stress. An integrated pH sensor tag was fabricated based on this low-voltage OFET, using an extended gate OFET for sensing and the other OFET as the load to convert the current signal to a voltage output for easy design of the subsequent readout circuit. With the low-voltage operation behavior and excellent operational stability of the OFET, the sensor tag was demonstrated to be operated in a 3.3 V battery powered electronic system for reliable pH sensing.