Sensitization of nanoporous TiO2 electrodes using the naturally occurring chromophores: stentorin and hypericin

This paper compares hypericin and stentorin as possible photosensitizers fo r transparent, nanoporous, TiO2-based photovoltaic cells. The absolute phot on conversion efficiency (APCE) of stentorin-sensitized nanoporous TiO2 ele ctrodes was 2%, 20 times greater than that of electrodes sensitized by the structural analog, hypericin (0.1%). We attribute the greater efficiency of the stentorin electrode to the decreased tendency of stentorin to aggregat e on the electrode surface. These results suggest that controlling aggregat ion by making a slight structural modification to the chromophore could be a viable and generalizable method for improving the performance of dye-sens itized electrodes. (C) 2001 Elsevier Science B.V. All rights reserved.