Data from: Direct quantification of ion composition and mobility in organic mixed ionic-electronic conductors

Ion transport in organic mixed ionic-electronic conductors (OMIECs) is
crucial due to its direct impact on device response time and fundamental
operating mechanisms but are often assessed indirectly or rely on extra
assumptions. Operando X-ray fluorescence (XRF) is a powerful, direct probe
useful for elemental characterization of bulk OMIECs, and was employed to
directly quantify ion composition and mobility in a model OMIEC,
PEDOT:PSS, during device operation. The first cycle revealed slow
electrowetting and cation-proton exchange. Subsequent cycles showed rapid
response with minor cation fluctuation (~5%). Comparison with
optical-tracked electrochromic fronts revealed a mesoscale structure
dependent proton transport. The calculated effective ion mobility
demonstrated thickness-dependent behavior, emphasizing an interfacial ion
transport pathway with a higher mobile ion density. The decoupling of bulk
and interfacial effects on ion mobility, and the decoupling of cation and
proton transport contributes to our understanding of ion transport in
conventional and emerging OMIEC-based devices, and has broader
implications for ion transport in other ionic conductors writ large.