Deposition Dependent Ion Transport in Doped Conjugated Polymer Films: Insights for Creating HighPerformance Electrochemical Devices

DOI: 10.1002/admi.201700873 transport.[20] When interfaced with an electrolyte, redox events in conjugated poly mer films are also accompanied by film swelling or deswelling due to ion and/or solvent diffusion into or out of the films, respectively. The response times and fatigue resistances of devices that subject electroactive films to periodic cycles of oxidation/reduction are, thus, crucially determined by solvent intercalation and/ or ion transport across an interface and mass trapping within the conductive poly mer layer.[21,22] Innovations in film deposition routines[23,24] and doping protocols have resulted in huge leaps in the electronic conductivities of doped conjugated poly mer films, even reaching the metallic regime in the composite material poly(3,4ethylenedioxythiophene)-co-poly(styrene sulfonic acid) (PEDOT:PSS).[25–27] However, correlated insights into how these processing conditions affect redox-associated swelling behavior and ion transport in doped conjugated polymer films (other than PEDOT:PSS) is lacking. This knowledge is integral for optimizing the performance of polymer-based hybrid supercapacitors and enabling accurate data interpretation from electrochemical transistors, among other applications.[28,29] In this work, we use simultaneous electrochemical and electrogravimetric measurements[30–34] to probe, in situ, the swelling behavior, permselectivity and electrochemical cycling stabilities[35–37] of a model material, p-doped PEDOT, in selected electrolytes. In particular, we pay attention to the effects of deposition method on the electrochemical and electrogravimetric properties of resulting films. Our efforts reveal that PEDOT films obtained using oxidative chemical vapor deposition display notable permselectivity and near-ideal redox-associated mass transport during repeated doping/dedoping cycles.