Mini-Review: Mixed Ionic-Electronic Charge Carrier Localization and Transport in Hybrid Organic-Inorganic Nanomaterials.

In this mini-review, a comprehensive discussion on the state of the art of hybrid organic-inorganic mixed ionic-electronic conductors (-MIECs) is given, focusing on conducting polymer nanocomposites comprising inorganic nanoparticles ranging from ceramic-in-polymer to polymer-in-ceramic concentration regimes. First, a brief discussion on fundamental aspects of mixed ionic-electronic transport phenomena considering the charge carrier transport at bulk regions together with the effect of the organic-inorganic interphase of hybrid nanocomposites is presented. We also make a recount of updated instrumentation techniques to characterize structure, microstructure, chemical composition, and mixed ionic-electronic transport with special focus on those relevant for -MIECs. Raman imaging and impedance spectroscopy instrumentation techniques are particularly discussed as relatively simple and versatile tools to study the charge carrier localization and transport at different regions of -MIECs including both bulk and interphase regions to shed some light on the mixed ionic-electronic transport mechanism. In addition, we will also refer to different device assembly configurations and measurements experiments to analyze mixed ionic-electronic conduction phenomena for different specific applications. Finally, we will also review the broad range of promising applications of -MIECs, mainly in the field of energy storage and conversion, but also in the emerging field of electronics and bioelectronics.