Flexible organic thin-film transistors based on poly(3-hexylthiophene) films for nitrogen dioxide detection

Flexible nitrogen dioxide (NO2) gas sensors based on organic thin-film transistors (OTFTs) were developed in this work, in which conductive indium tin oxide (ITO) coated polyethylene naphthalene-2,6-dicarboxylate (PEN) was designed for the flexible substrates, and poly methyl methacrylate (PMMA) and poly(3-hexylthiophene) (P3HT) was spin-coated as the gate dielectric layer and spray-deposited as the active layer, respectively. The effects of PMMA concentrations and P3HT solution volume on performances of flexible OTFTs were systematically investigated. The results showed that the optimized flexible OTFT exhibited high field-effect mobility (9.51×10–3 cm2/(V s) at a gate bias of –50 V) and excellent response characteristics, including high sensitivity (up to 0.169 ppm–1), good repeatability and selectivity. The flexibility of the developed OTFT sensor was also investigated, and the results showed that the electrical and gas-sensing properties were affected by the bending cycles, thus further work should be done for improving the flexibility of the sensor. This work provides an effective approach in developing high performance flexible OTFT NO2 gas sensor.