Novel dye sensitizers of main chain polymeric metal complexes based on complexes of diaminomaleonitrile with Cd(II), Ni(II): Synthesis, characterization, and photovoltaic performance for dye-sensitized solar cells

Four new donor-π-acceptor (D-π-A) dyes (P1, P2, P3, P4) were synthesized, characterized and applied in dye-sensitized solar cells (DSSCs). Poly(p-phenylenevinylene) (PPV) or Bisthien PPV was used as donor, ethilenic link or thiophene as π-bridge, and Cadmium complexes or Nickel complexes as acceptor in these D-π-A type sensitizers. The introduction of the polymerization of π system and the metal complexes has greatly increased the light absorption. Increasing the number of thienyl group in the molecule to a certain extent was effective in further lowering both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels to attain higher open-circuit voltage (Voc). Among them, P3-based cell shows excellent photovoltaic performance and power conversion efficiency up to 2.25% under AM 1.5G irradiation (100 mW cm−2).