What Drives the Kinetics and Doping Level in the Electrochemical Reactions of PEDOT:PSS?

Abstract The electrochemical dedoping and redoping processes of a thin poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film immersed in an electrolyte are studied at different temperatures with time‐resolved spectroelectrochemistry in the visible and near‐infrared range. The spectral signatures of neutral, polaronic, and bipolaronic states of PEDOT are resolved using multivariate curve resolution analysis. Kinetic modeling of their dynamics reveals that both the dedoping and redoping are sequential processes and occur within a few hundred milliseconds in the system. Evaluation of the temperature‐dependence with the Van't Hoff, Arrhenius, and Eyring formalisms highlights the role of entropy in both the establishment of the redox equilibrium at a given voltage bias and the reaction rates. This study provides a significant understanding of the fundamental mechanisms determining the level and rate of the electrochemical processes in PEDOT:PSS and will help tailor the design of faster and more efficient bioelectronic devices based on mixed ionic–electronic conductors.