Time-Resolved Structural Dynamics of Organic Mixed Ionic Electronic Conductors

The structure and packing of organic mixed ionic-electronic conductors have an outsized effect on transport properties. In operating devices this structure is not fixed but is responsive to changes in electrochemical potential, ion intercalation, and solvent swelling. Towards this end, the dynamic structure of a model organic mixed conductor is characterized using multimodal time-resolved operando techniques. Time-resolved operando X-ray scattering reveals asymmetric rates of structural change during doping and dedoping that do not directly depend on potential or charging dynamics. Time-resolved spectroscopy establishes a link between structural transients and the complex dynamics of electronic charge carrier subpopulations, in particular the polaron-bipolaron equilibrium. These findings provide insight into the factors limiting the response time of organic mixed conductor based devices, and present the first real-time observation of the structural changes during doping and dedoping of a conjugated polymer system via X-ray scattering.