Enhanced energy and quantum efficiencies of a nanocrystalline photoelectrochemical cell sensitized with a donor-acceptor dyad derived from fluorescein

The dye-sensitized photovoltaic cells were prepared by using donor-acceptor dyads derived from fluorescein. The photovoltaic measurements were performed using a standard two-electrode system consisting of a working electrode and a Pt sputtered electrode in air-saturated methoxyacetonitrile containing 0.5 M iodide and 0.05 M I₂. The xanthene dye-sensitized photovoltaic cells of the charge-separation type exhibit significant enhancement in the photoelectrochemical performance as compared with those of fluorescein without the charge-separation unit. The overall power conversion efficiency (ν = 1.6%) has been attained by using a fluorescein derivative composed of an electron donor (diphenylanthracene) unit and an acceptor unit (difluoroxanthene), assembled on a ZnO-SnO₂ composite film as an oxide semiconductor.