Kinetics and Physicochemical Characteristics of Electrodeposited PEDOT:PSS Thin Film Growth

In bioelectronics, conducting polymer coatings allow the reduction of the impedance of metallic electrodes and facilitate the translation of bioelectrical signals at their interface. Such coatings can be made using thin film deposition from a solution or direct synthesis via electrodeposition. The electrical control over the deposition offers the possibility for a fine-tuning of the film's thickness and structure. However, the mechanical stability of such coatings mainly suffer from their poor adhesion to the electrode surface and film cracking. Here, an extended study on the kinetics of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electropolymerization and the evolution of its physicochemical properties is provided. The impedance spectroscopy closely follows the electrochemical variations during the PEDOT:PSS's film growth, described by modeled equivalent circuits. The film's properties change during polymerization in relation to the supporting electrode size, its surface chemistry, and the deposition time. The film growth structures polymeric morphology in a confluent layer with a strong thickness increase before reaching its mechanical surface failure. Before this point, the film remains stable over a hundred cycles of applied potential strain in a defined redox window. These evaluations benchmark the PEDOT:PSS film properties during its electropolymerization toward electrochemically tunable transducers for bioelectronics.