Novel carbazole-based main chain polymeric metal complexes containing complexes of phenanthroline with Zn(II) or Cd(II): Synthesis, characterization and photovoltaic application in DSSCs

In this work, four main chain polymeric complexes(P1–P4), with fluorene or phenylethyl linked with carbazole as electron donor, phenanthroline metal complexes as a electron withdrawing unit, were synthesized through simple synthetic procedures and with low cost. They were characterized by FT-IR, Elemental analysis, GPC. The UV–vis absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry are also determined and studied. Dye-sensitized solar cells (DSSCs) based on P1–P4 as the dye sensitizers exhibit some conversion efficiencies. It was found that the incorporation of 2,7-divinyl-9,9-dioctylfluorene unit instead of 1,4-divinyl-2-methoxyl-5-octyloxybenzene unit results in a negative shift of the lowest unoccupied molecular orbital(LUMO) levels for P3 and P4, in comparison to P1and P2, which induces a remarkable enhancement of the electron injection driving force from the excited polymer sensitizers to the TiO2 semiconductor. Moreover, when the coordinated ion of the polymer complexes changed from zinc ion to cadmium ion, a bathochromically shifted maximum absorption band can be realized, which consequently results in an increased light harvesting efficiency and photogenerated current. All of these dyes performed as sensitizers for the DSSCs test under AM 1.5 similar experimental conditions, and a maximum solar-to-electric power-conversion efficiency (PCE) is up to 1.15% (Jsc = 2.71 mA cm−2, Voc = 0.649 eV, FF = 0.653).