An electrical characterisation system for the real-time acquisition of multiple independent sensing parameters from organic thin film transistors

Abstract

The presence of multiple independent sensing parameters in a single device is the key conceptual advantage of sensor devices based on an organic thin film transistor (OTFT) over simple organic chemiresistors. Practically, however, these multiple parameters must first be extracted from the electrical characteristics of the OTFTs and, thus, they are not immediately apparent. To exploit the advantage of OTFT sensors, we require a measurement technology to extract these parameters in real time. Here, we introduce an efficient, cost-effective system that is a faster and more compact alternative to the expensive and cumbersome laboratory-based instruments currently available. The characterisation system presented here records the electric behaviour of OTFTs in the form of its "saturated transfer characteristics" multiple times per second for virtually unlimited periods of time, with the option to multiplex up to 20 devices in parallel. By applying a bespoke algorithm to the measured transfer characteristics, the system then extracts, in real time, several underlying transistor parameters (on-and off-current, threshold voltage, and charge carrier mobility). Tests were conducted on the example of a poly(thieno[3,2-b]thiophene) (PBTTT) OTFT exposed to ethanol vapour. The system extracts the underlying OTFT parameters with very low noise without introducing apparent correlations between independent parameters as an artefact.