Actuation and Charging Mechanisms of Thin <scp>PEDOT</scp> : <scp>PSS</scp> Films Probed by Electrochemical <scp>AFM</scp> and Impedance Spectroscopy

ABSTRACT PEDOT:PSS is a widely applied material in the field of organic electronics. Due to its mixed ionic‐electronic conductivity, it is popular for soft actuators based on stimulated ion exchange. However, for confined spaces like thin films, interfaces play an important role in the actuation. Hence, we studied the actuation behavior of thin films of PEDOT:PSS with film thicknesses ranging from 100 nm up to 3 μm by atomic force microscopy. We observed a decrease in the relative expansion for thicker films. Moreover, the volume charge density also decreased. Electrochemical impedance spectroscopy granted more insight into film charging. We observed significant differences between oxidized and reduced films. We described ion diffusion by a pseudo‐capacitance, which also decreased for thicker films. Hence, we conclude a limitation in thin PEDOT:PSS films affects the charging and the actuation.