Tuning PEDOT:PSS low-impedance thin films with high charge injection for microelectrodes applications

The use of conductive polymers as thin films has become increasingly popular for a vast array of applications, such as biomedical in the form of microelectrodes, energy harvesting, thermal and electrical solutions. In this work, we studied the effects of different concentrations ratios of monomer 3,4-ethylenedioxythiophene (EDOT) to poly(4-styrenesulfonate) (PSS) and two distinct modes of electrochemical deposition (Potentiodynamic and Potentiostatic) to polymerize and deposit PEDOT:PSS (Poly-(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)). The produced thin films were morphologically and electrochemically characterised. The 1:5 ratio of EDOT to PSS from the Potentiostatic mode showed the highest charge storage capacity, better phase response which translated into larger charge injection capabilities without deformation of the original current input and a lower impedance. The comparison with a gold (Au) thin film highlights both the increased capacity to store charge and deploy it safely, within the water catalysis window. Furthermore, the impedance magnitude for the PEDOT:PSS sample was vastly reduced, with the impedance phase revealing an ohmic behaviour for the PEDOT:PSS sample contrasting with a capacitive behaviour for the Au sample. These results demonstrate that PEDOT:PSS is highly promising for 2D and 3D microelectrode applications and, most importantly, show the advantage of tuning the polymerization of PEDOT:PSS instead of using pre-made solutions in conjunction with a facile method of electrodeposition.