Organic field effect transistor based on polyaniline - dodecylbenzene sulphonic acid for humidity sensor

Humidity sensor based on organic field-effect transistor (OFET) was created using P-channel organic semiconductor polyaniline doped with dodecylbenzene sulfonic acid (DBSA)(1∶2.5) as an active layer and gate insulator polymethyl methacrylate (PMMA) layer on n-type silicon gate. The performance of OFET was evaluated using current-voltage characteristics (I–V) under exposure to humidity. The p-type OFETs operating in an enhancement mode with the current saturation (ISat) was 2.6 µA and the threshold voltage VT was found to be 2.4V. The OFET sensors exhibited a change in the electric characteristic such as the threshold voltage, the saturation current, and the field-effect charge carrier mobility when the sensors were exposed to Relative humidity (RH). Meanwhile, the favourable and rapid change in humidity response characteristics of the OFET sensors was observed from the change in the drain-source current as a function of time. After exposed to relative humidity, the drain current of sensor was enhanced due to the decrease of the channel resistance. When the sensors were exposed to 93.4 % RH the drain current was saturated.