Enhanced flexible room temperature ammonia sensor based on PEDOT: PSS thin film with FeCl3 additives prepared by inkjet printing

Herein we report improved ammonia (NH3) gas sensing properties based on poly (3,4-ethylene-dioxythiophene)poly(styrenesulfonate) (PEDOT: PSS) thin films with ferric chloride (FeCl3) as additives, which were prepared by inkjet printing the PEDOT: PSS solution and FeCl3 aqueous solution onto the flexible polyimide films in sequence. PEDOT: PSS based gas sensing films with different thickness and different content of FeCl3 were formed. The morphologies and electrical properties of these films were investigated by scanning electron microscope, X-ray photoelectron spectroscopy and an instrument designed to measure the gas sensing abilities of the films. The results showed that the addition of FeCl3 to the PEDOT: PSS (FeCl3-PEDOT: PSS) thin film improved the NH3 sensing performance of the sensor significantly. The response value was increased tenfold to approximately 44%, and the response time was reduced by 30 times to 20 s than those of the pure PEDOT: PSS film for detecting 50 ppm NH3 at 20 degrees C. Furthermore, the lower detectable NH3 concentration of the FeCl3-PEDOT: PSS thin film sensor was 0.5 ppm at room temperature with the response value of 7.6%. Additionally, the FeCl3-PEDOT: PSS thin film sensor presented excellent flexible stability, showing only minor response value changes with different bending angles. The results reveal the potential application of flexible based sensor for monitoring NH3 gas under ambient conditions and show that ink-jet printing is a simple and low-cost method to prepare flexible gas sensing films with controlled film thickness and additive level.