Synthesis and photovoltaic performance of novel polymeric metal complex sensitizer with benzodithiophene or carbazole derivative as donor in dye-sensitized solar cell

Abstract

Four donor-acceptor (D-A) types of novel conjugated polymeric metal complex dyes (P1–P4) with Zn (II) or Cd (II) complexes as the electron acceptors and benzodithiophene or carbazole derivative as the electron donors were designed and prepared, as promising sensitizers for dye-sensitized solar cells (DSSCs). Diaminomaleonitrile acted as ancillary ligand. The structures of the polymers were confirmed, and their thermal, optical, electrochemical, and photovoltaic properties were investigated. All conjugated polymers exhibit good thermal stability with onset decomposition temperatures with 5% weight loss over 315 °C, broad absorption with the onset of absorption at 588 nm in the visible region, and relatively lower HOMO energy levels from −5.54 to −5.71 eV. The DSSC device based on P2 which containing Cd(II) as coordination metal ion and benzodithiophene derivative as donor exhibited the highest power conversion efficiency of 2.18% under the AM 1.5 G (100 mW cm−2) sunlight illumination with an open-circuit voltage of Voc = 0.68 V, a short current density of Jsc = 4.85 mA cm−2, and a fill factor of FF = 66.2%, respectively. Therefore, these results provide a new way to design dye sensitizers for DSSCs.