Bimodal functioning of a mesoporous, light sensitive polymer/electrolyte interface

Interfaces between conjugated polymers and aqueous electrolytes are gaining increasing interest for a number of different applications, including electrochemical cells, biosensors and functional organic devices for recording and stimulating the bioelectrical activity. In this field, devices sensitive to visible light are particularly interesting, both for inducing solar-driven photo-electrochemical reactions and for spatially selective, not-invasive optical control of living systems. We demonstrate that photoexcitation of the conjugated polymer leads to both capacitive and faradaic electrical signals at the interface with water. We introduce here a mesoporous, light sensitive polymer/electrolyte interface, we characterize its behavior and we reproduce the experimental data with an equivalent circuit model. Interestingly, we show that the use of polymer-based mesoporous devices offers a practical and simple handle for the modulation of the interface behavior. Device engineering allows to control the sign of charges at the polymer surface and to balance faradaic and capacitive currents established at the interface with water. This work opens up interesting opportunities towards applications in both photo-electrochemistry and biology.