The main focus of present studies on dye-sensitized solar cells (DSSCs) is based on the sensitization of n-type semiconductors, which consist of photoactive anodes and passive cathodes (n-type DSSCs). However, DSSCs in which the cathode is photoactive are also possible and the development of photocathode can provide an entry to the preparation of a tandem solar cell.
In this presentation we will show a new organic dye (P1) which can be used in sensitization of p-type DSSCs. In P1, we use triphenylamine moiety as the electron donor, malononitrile moiety as the electron acceptor and thiophene unit as the conjugated linker. By introducing two electron acceptor groups and having the anchoring group on the donor moiety, light excitation is associated with electron flow from the donor part of the dye to the acceptor part, providing efficient electron transfer pathway from the dye to the electrolyte.
P1 has very high extinction coefficient and under AM 1.5 irradiation, the highest incident photo-to-current conversion efficiency (IPCE) of 18% in visible region has been obtained in the preliminary tests based on the NiO₂ film. This is the highest value so far in p-type DSSCs. Now we are optimizing the p-type systems and we hope that we can get a better efficiency in p-type DSSCs in the future.