Donor−Acceptor Nanoarchitecture on Semiconducting Electrodes for Solar Energy Conversion

Donor−acceptor molecules have been fabricated on a nanostructured semiconducting electrode for solar energy conversion (i.e., dye-sensitized bulk heterojunction solar cell). The device structure is similar to that of dye-sensitized solar cells, but the top surface of the nanostructured semiconducting electrode is covered with donor−acceptor multilayers. Thus, initial charge separation takes place at the blend interface of the donor−acceptor, which is a typical characteristic of bulk heterojunction solar cells, whereas subsequent processes resemble those in dye-sensitized solar cells. In this novel solar cell, donor-nanocarbons (i.e., fullerenes and carbon nanotubes) have been successfully deposited electrophoretically or spin-coated onto nanostructured SnO2 and TiO2 electrodes that exhibit efficient photocurrent generation. The bottom-up self-organization of porphyrin and fullerene molecules onto the nanostructured electrodes has led to moderate cell performance with an incident photon-to-current efficiency of up to ∼60% and a power conversion efficiency of 1−2%. Importance of donor−acceptor nanoarchitecture on the nanostructured semiconducting electrodes is highlighted in terms of self-assembly of donor−acceptor molecules.