In the study to improve the light absorption range and
intensity
of dye sensitizers in the visible region and promote their photovoltaic
performance, five novel polymeric metal complexes with sulfur coordination
(BDTT-VBT-Ni, BDTT-VBT-Cu, BDTT-VBT-Zn, BDTT-VBT-Cd, and BDTT-VBT-Hg)
to be used as D–A−π–A motif dye sensitizers
were designed, synthesized, and characterized. In these polymeric
metal complexes with sulfur coordination, the metal complexes with
sulfur coordination of benzodithiophene derivatives are used as auxiliary
electron acceptors, 8-quinolinol derivatives are used as π-bridge
and electron acceptors, and thienylbenzene-[1,2-b:4,5-b′] dithiophene (BDTT) are used as electron
donors. The effect of different metal complexes with sulfur coordination
on the photovoltaic performance of dye sensitizers has been systematically
studied. Under AM 1.5 irradiation (100 mW cm–2),
the devices of dye-sensitized solar cells (DSSCs) based on five polymeric
metal complexes with sulfur coordination exhibited a short-circuit
current density (J
sc) of 13.43, 15.07,
18.00, 18.99, and 20.78 mA cm–2, respectively, and
their power conversion efficiencies (PCEs) were 7.10, 8.59, 10.68,
11.23, and 12.89%, respectively, and their thermal decomposition temperatures
(T
d) were 251, 257, 265, 276, and 277
°C, respectively. The result shows that the J
sc and PCE of five polymeric metal complexes increase
by degrees, and the PCE of BDTT-VBT-Hg is up to 12.89%, which is because
of the strength of the coordination bonds between Ni(II), Cu(II),
Zn(II), Cd(II), and Hg(II) and sulfur increases in turn so that the
electron-withdrawing ability and electron-transfer ability of auxiliary
electron acceptors is enhanced. These results provide a new way to
develop stable and efficient metal complexes with sulfur coordination
dye sensitizers in the future.