Electrolyte/Dye/TiO Interfacial Structures of Dye-Sensitized Solar Cells Revealed by Neutron Reflectometry with Contrast Matching.

The nature of an interfacial structure buried within a device assembly is often critical to its function. For example, the dye/TiO interfacial structure that comprises the working electrode of a dye-sensitized solar cell (DSC) governs its photovoltaic output. These structures have been determined outside of the DSC device, using characterization methods; yet, they really should be probed while held within a DSC since they are modulated by the device environment. Dye/TiO structures will be particularly influenced by a layer of electrolyte ions that lies above the dye self-assembly. We show that electrolyte/dye/TiO interfacial structures can be resolved using neutron reflectometry with contrast matching. We find that electrolyte constituents ingress into the self-assembled monolayer of dye molecules that anchor onto TiO. Some dye/TiO anchoring configurations are modulated by the formation of electrolyte/dye intermolecular interactions. These electrolyte-influencing structural changes will affect dye-regeneration and electron-injection DSC operational processes. This underpins the importance of this structural determination of electrolyte/dye/TiO interfaces within representative DSC device environments.