Gas sensors based on poly-3-hexylthiophene thin-film transistors

Abstract

A thin-film field-effect transistor with an organic semiconductor as the channel material was demonstrated. Spin-coated regioregular poly-3-hexylthiophene (P3HT) thin films show conducting characteristics with holes as carriers. The transistor showed a field-effect mobility of 1.1 cm 2/V s and an on/off ratio of 50 in the accumulation mode. No ideal device characteristics were obtained in the depletion mode. A change in drain current ( I d) was observed when device was exposed to small amounts of nitrous oxide (N 2O) gas. The total variation in the I d was 0.35 mA. Using the transistor, it was possible to detect 1000 ppm of N 2O gas with a response time of less than 1 min at 50 °C. A similar device response was not observed after oxygen exposure. N 2O gas was found to affect the charge transport properties of the poly-3-hexylthiophene film. The presence of polar molecules is known to change the rate of charge transport in organic materials by increasing the amount of energetic disorder through charge–dipole interactions.