The response characteristics of a gas sensor based on poly-3-hexylithiophene thin-film transistors

This paper studies the response characteristics of a gas sensor for organic thin-film transistors (OTFTs), made from spin-coated poly-3-hexylthiophene (P3HT) on a thermally grown SiO2/Si wafer. The gas response characteristics of OTFT sensors are observed from the change in the drain–source current, as a function of time, when the P3HT-based OTFT sensors of different channel widths are exposed to cycles of exposure to and the evacuation of NH3 gas, with concentration ranging from 10 to 100 ppm at room temperature in normal atmosphere. The measured drain–source current decreases rapidly with time after exposure to NH3 gas and the response characteristics of the drain–source current are seen to be higher for larger values of NH3 gas concentration. Also, the response characteristics of the OTFT sensor show that there is a shift in the threshold-voltage as well as a change in mobility after exposure to NH3 gas.