Dye sensitizers of polymer using the complex of Cd (II) or Cu (II) with imidazole as auxiliary electron acceptor for dye-sensitized solar cells

To enhance the absorption intensity and extend the absorption range of dye sensitizers in visible and near infrared region, as well as to promote the photovoltaic performances, four novel D−A−π−A motif dye sensitizers of polymeric metal complex (PFL-BP-Cd, PFL-BP-Cu, PBDTT-BP-Cd and PBDTT-BP-Cu) using the complexes of Cd(II) or Cu(II) with imidazole as auxiliary electron acceptors, thienylbenzo[1,2-b:4,5-b'] dithiophene (BDTT) or fluorine (FL) derivative as electron donor (D), and 8-quinolinol derivative as π bridge and acceptor, have been designed and synthesized firstly. Their thermal, optical, electrochemical properties and photovoltaic performance in dye-sensitized solar cells (DSSCs) were also investigated. The results show that the four dye sensitizers of polymeric metal complex have relatively strong light absorption and high photovoltaic performance among dye sensitizers of polymers. The UV-Visible absorption spectra indicates obvious red-shift of PBDTT−BP−Cd compared with the others, and the device sensitized by PBDTT−BP−Cd exhibited the highest power conversion efficiency (PCE) of 6.13% under the full sunlight (AM 1.5 G, 100 mW cm−2) irradiation. In addition, all dyes show outstanding thermal stability(Td > 300 °C). The results reveal a new path to design efficient dyes of polymer for DSSCs.