Mechanisms of Polythiophene Chemical Sensors

Chemical sensors based upon regioregular polythiophene thin-film transistors (TFT) are studied for their chemical sensing properties to volatile organic compound vapors. The sensing properties are found to be highly dependent upon the TFT operating conditions. As the applied gate voltage is varied the source-drain current response can differ both in sign and magnitude for the same analyte. This implies that multiple sensing mechanisms co-exist. Here, we propose that the two main sensing mechanisms are mainly due to a dipole interaction effect, which occurs inside the crystallites and yields a positive response, and a grain boundary (GB) effect, which yields a negative response.