Humidity Sensor Based on PEDOT:PSS and Zinc Stannate Nano-composite
A composite of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and zinc stannate (ZnSnO3) has been introduced for impedance-based humidity sensing, owing to its high sensitivity, good stability, very fast response (∼0.2 s) and recovery time (∼0.2 s), small hysteresis, repeatability, low-cost fabrication and wide range of sensitivity. Both materials were mixed in three different weight percentage ratios, to optimize the performance of the sensors. Best response was observed for 5 wt.% PEDOT:PSS and 5 wt.% ZnSnO3. The impedance of the sensor was dropped immensely from 1.5 MΩ to 50 kΩ by changing relative humidity from 0% to 90%. The reason for this improvement in sensitivity was analyzed by virtue of sensing mechanisms and different characterizations (three dimensional (3D) nano-profiler, optical microscope, and fourier transform infra-red (FTIR) spectroscopy) revealing the surface morphology and chemical structure of the film. Due to its response and ability to sense human breath and skin humidity, it is suitable for environmental, artificial skin and food industry applications.