Deposition Dependent Ion Transport in Doped Conjugated Polymer Films: Insights for Creating High‐Performance Electrochemical Devices

Charge conduction and redox events in films of doped conjugated polymers are necessarily accompanied by counterion transport. However, insights into how deposition conditions affect ion transport in a structurally diverse set of doped conjugated polymer films and across a polymer/electrolyte interface have not been gathered. Here, cyclic voltammetry and electrogravimetry measurements are used to probe solvent and ion transport across a doped conjugated polymer/electrolyte interface. A representative polymer, p ‐doped poly(3,4‐ethlyenedioxythiophene) (PEDOT), obtained using two different deposition methods, vapor phase polymerization (VPP) and oxidative chemical vapor deposition (oCVD), is studied. PEDOT films obtained via VPP and oCVD display dissimilar morphologies at the micro‐ and nanometer length scales, resulting in significantly differing swelling behavior, mass trapping, and ion transport upon exposure to a periodic applied potential. PEDOT films obtained using oCVD display notable permselectivity and near‐ideal mass transport during repeated doping/dedoping cycles in various electrolytes, indicating that these films are robust electroactive materials. This study underlines the extent to which film deposition conditions affect ion transport across polymer/electrolyte interfaces and provides insights into optimal film forming conditions for high‐performance supercapacitors and electrochemical transistors.