Photovoltaic performance of dye-sensitized solar cells based on a series of new-type donor–acceptor π-conjugated sensitizer, benzofuro[2,3-c]oxazolo[4,5-a]carbazole fluorescent dyes

A series of new-type donor–acceptor π-conjugated benzofuro[2,3-c]oxazolo[4,5-a]carbazole fluorescent dyes with substituents such as various lengths of non-conjugated alkyl chains containing a carboxyl group at the end position, π-conjugated carboxyl, cyano and dibutylamino groups are designed and synthesized. Dye-sensitized solar cells were fabricated using these dyes. The influence of configuration of the dyes on TiO2 surface and chemical structures of the dyes on the photovoltaic performance are investigated and discussed on the basis of semi-empirical molecular orbital calculations (AM1 and INDO/S). It is concluded that a carboxyl group of donor–acceptor π-conjugated sensitizer is necessary not as the electron acceptor, but only as anchoring group for attachment on TiO2 surface. Therefore, it was proposed that the most important point for developing new and efficient donor–acceptor π-conjugated sensitizers for DSSCs is to design dye molecules capable of forming a strong interaction between the electron acceptor moiety of sensitizers and TiO2 surface.