Gas sensing properties of poly-3-hexylthiophene thin film transistors

A thin-film field-effect transistor (TFT) with an organic semiconductor as the channel material was demonstrated. Cast-coated regioregular poly-3-hexylthiophene (P3HT) thin film shows conducting characteristics with holes as carriers. The output characteristics of TFTs showed a field-effect mobility of 21.4 cm2/Vs and an on/off ratio of 100 in the accumulation mode. No ideal device characteristics were obtained in the depletion mode. A change in drain current (Id) was observed when device was exposed to small amounts of nitrous oxide (N2O) gas. The total variation in the Id was 27 μA. Using the TFTs, it was possible to detect 1000 ppm of N2O gas at room temperature. N2O gas was found to affect the charge transport properties of the P3HT film.