Photoinduced electron transfer in multilayer self-assembled structures of porphyrins and porphyrin-fullerene dyads on ITO

A new strategy for constructing well-ordered, self-assembled multilayer structures of photoactive donor-acceptor systems has been developed. In this approach indium-tin oxide (ITO) electrodes were modified with successive self-assembled monolayers of Zn porphyrins (ZnP) and free-base porphyrin-fullerene (H2P-C-60) dyads to obtain oriented triad configurations. All the layers were attached with two molecular linkers to achieve an organized composition. The multilayer structures were found to enhance the photocurrent and photovoltage generation compared to monolayers of the same compounds. Particularly, combining a densely packed ZnP layer with the highly oriented H2P-C-60 dyad layer resulted in 280 times higher photovoltage response than measured for a monolayer of the dyad. Furthermore, both photovoltage and photocurrent were generated in the desired direction pursued with the sample orientations and, as a result of the organization, almost ideal current-voltage curves were formed.