Scanning electrochemical microscope studies of dye regeneration in indoline (D149)-sensitized ZnO photoelectrochemical cells

A scanning electrochemical microscope (SECM) in the feedback and generation-collection modes was used to investigate the regeneration of photoexcited dye cations at the semiconductor/electrolyte interface in a dye-sensitized solar cell (DSSC) based on ZnO/D149. An effective dye regeneration rate constant kox of 9.55 × 107 cm9/2 mol−3/2 s−1 was obtained from feedback mode experiments at different wavelengths and light intensities on ZnO/D149 electrodes. Illuminated regions of the dye-sensitized electrodes could be differentiated from non-illuminated regions by local imaging in SECM generation-collection experiments with I- as redox mediator. We also report SECM feedback measurements on non-illuminated dye-sensitized electrodes to investigate the electron transfer kinetics of dissolved redox couples at the underlying FTO substrate.