Organic Transistor Based on Cyclopentadithiophene-Benzothiadiazole Donor-Acceptor Copolymer for the Detection and Discrimination between Multiple Structural Isomers

Distinguishing structural isomers is a critical and challenging task for biotechnology, chemical industry, and environmental monitoring. Approaches currently available are limited in terms of selectivity and simplicity. In this paper, a highly sensitive organic field-effect transistor (OFET) using the cyclopentadithiophene-benzothiadiazole (CDT-BTZ) copolymers as a semiconductor is presented for easy and selective detection of different families of structural isomers, as well as between different isomers within each family. High accuracy discrimination is achieved over a range of concentrations using only a single sensing parameter derived from the OFET characteristic transfer curve. As a reference, other homopolymer- and donor-acceptor copolymer-based OFET sensors are examined but do not have an equivalent sensing performance to that of the CDT-BTZ-based OFETs. Investigating the link between isomer absorption and swelling, supramolecular order and energy levels of the active layer reveals a unique effect of each isomer on the energy bands of the semiconducting polymer.