Novel D-π-A dye sensitizers of polymeric metal complexes based on Cd(II) with salicylaldehyde and diaminomaleonitrile: synthesis, characterization, and photovoltaic performance for dye-sensitized solar cells

Being a key component of dye-sensitized solar cells, dye sensitizer and its synthesis and application have been extensively researched. In this paper, four novel polymeric metal complexes as dye sensitizers based on Cd(II) with salicylaldehyde and diaminomaleonitrile were functionally designed and synthesized. These dyes use poly(p-phenylenevinylene) or bithiophene phenylenevinylene as electron donor, Cd(II) complex unit as electron acceptor, and ethylenic bond as pi linker. They were characterized by FT-IR, H-1 NMR, gel permeation chromatography, and elemental analysis. Their thermal, photophysical, electrochemical, and photovoltaic properties were also investigated by thermogravimetric analysis, differential scanning calorimetry, C-V curves, and J-V curves. All four polymeric metal complexes exhibited some photovoltaic performances. The dyes containing bithiophene (P2, P4) exhibited higher power conversion efficiency (PCE) values than the corresponding polymers without thiophene unit (P1, P3). Dual-core cadmium polymeric metal complexes showed higher PCE than mononuclear cadmium complexes by comparing P4 with P2 as well as P3 with P1. The highest PCE of compound P4 reached 2.07 % (J (sc) = 4.22 mA/cm(2), V (oc) = 0.71 mV, and FF = 69.1 %) under simulate AM 1.5G solar irradiation.