Improved Sensitivity of Inkjet-Printed PEDOT:PSS Ammonia Sensor With “Nonideal” Morphology

Piezoelectric inkjet printing is used for fabricating poly (3,4-ethylene-dioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) ammonia (NH
₃
) sensors; it has the advantages of drop-on-demand maskless manufacturing, great material saving, and compatibility with large area flexible substrates. Different from previous research efforts on forming line structures of smooth surface and even edge, this article shows that the inkjet-printed PEDOT:PSS line structures with “nonideal” morphology of scalloped edges can bring benefits of improved sensitivity. By simply controlling the drop spacing, narrower and thinner local regions are formed between adjacent ink drops in the fabricated line structures. Adsorption of NH
₃
gas molecules onto any of these regions, causing hole depletion, can significantly affect the carrier transport, thus improving sensitivity. Inkjet-printed PEDOT:PSS sensors present obviously improved response compared to the spin-coated ones. Compared to that of devices with smooth and straight lines, the responsivity of the devices at a drop spacing of 40 μm is improved by nearly threefold.