Novel polymeric metal complexes of pyridine derivatives for being used as dye sensitizers

Abstract

The eight polymeric metal complexes in both series (BDTT-PP-Cd, BDTT-PP-Zn, BDTT-PP-Cu, BDTT-PP-Ni and BDTT-PBD-Cd, BDTT-PBD-Zn, BDTT-PBD-Cu, BDTT-PBD-Ni) for being used as D-A-(π-A)2 motif dye sensitizers were designed, synthesized and characterized. They use metal complex of pyridine derivatives as auxiliary electron acceptor, thienylbenzene-[1,2-b:4,5-b' dithiophene (BDTT) as electron donor, and 8-quinolinol derivatives as π-bridge and electron acceptor. Under AM 1.5 irradiation (100 mW cm−2), the devices of dye-sensitized solar cells (DSSCs) based on eight polymeric complexes exhibited short circuit current density (Jsc) of 17.39, 15.10, 14.03, 12.61 mA cm−2 and 18.95, 15.58, 14.53, 13.23 mA cm−2 respectively,and their power conversion efficiency (PCE) are 8.94%, 8.09%, 6.87%, 6.34% and 9.76%, 8.55%, 7.02%, 6.51% respectively. The photovoltaic performance test of DSSCs based on eight polymeric metal complexes showed that the PCE of BDTT-PBD-M (M = Cd, Zn, Cu, Ni) is higher than that of BDTT-PP-M (M = Cd, Zn, Cu, Ni) because of the introduction of the methyl group into BDTT-PBD-M and the increase of the absorption coefficient of the dye. For dye sensitizers with the same ligand and different metals, the PCE of BDTT-PP-Ni, BDTT-PP-Cu, BDTT-PP-Zn and BDTT-PP-Cd increase in order, and so does the other series BDTT-PBD-M. It is because of enhancing electron-withdrawing ability of auxiliary electron acceptor with the strength of coordination bond from Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ) and Cd(Ⅱ) with the ligand. These results provide a new way to develop efficient and stable dye sensitizers in the future.