There has been intense interest and debate concerning the electron transfer rates within dye-sensitized nanostructured n-type semiconductors (such as TiO2). The motivation for this research has been the development of solar cells in which the first step is electron injection from the dye's excited state into the semiconductor conduction band. Our system, however, is designed such that hole injection from an excited mol. into a p-type nanostructured semiconductor can occur. An IPCE (incident photon-to-current conversion efficiency) of 3% has already been reported for a nanostructured NiO film dye-sensitized with erythrosin B (He, J.; Lindstrom, H.; Hagfeldt, A.; Lindquist, S.-E. J. Phys. Chem. B. 1999, 103, 8940). It is not possible for electron injection to occur from the excited dye into NiO because the conduction band of NiO is significantly higher in energy than electrons in the dye's excited states. However, the energies of both the dye's HOMO and the redox electrolyte lie below the NiO valence band energy, making electron injection from NiO into either the dye or the electrolyte possible. This study investigates the dynamics at the NiO/dye/electrolyte interface using time resolved optical spectroscopy.