Synthesis and characterization of stable main-chain polymeric metal complex dyes based on phenothiazine or carbazole units for dye-sensitized solar cells

Four novel polymeric metal complex dyes (P1-P4) based on phenothiazine or carbazole derivatives, containing complexes of diaminomaleonitrile with Zn(II) or Co(II) were synthesized and characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, UV-visible absorption, cyclic voltammetry and elemental analysis. The dyes based on carbazole derivatives (P3, P4) exhibited wider absorption spectra, and after replacement of the Co(II) coordinated ion with Zn(II), a bathochromic shift in the absorption spectrum was observed. When used in dye-sensitized solar cells (DSSCs), the device sensitized by P3 exhibited the best photocurrent conversion efficiency (2.06%) under standard illumination with a short-circuit photocurrent density (J(sc)) of 4.54 mA cm(-2), an open-circuit photovoltage (V-oc) of 0.67 V and a fill factor (ff) of 67.8%. Moreover, these dyes all exhibited excellent chemical and thermal stability. These results reveal a new path for the design of novel conjugated organic polymer dyes for highly efficient DSSCs.