Ferrocene Appended Asymmetric Sensitizers with Azine Spacers with phenolic/nitro anchors for Dye-Sensitized Solar Cells

Two extensively conjugated asymmetric ferrocene appended compounds with azine spacers, and phenolic and nitro groups as terminal groups with the following formulas Fc-CH=N-N=CH-p-C₆H₄-OH (Fc-OH) and Fc-CH=N-N=CH-p-C₆H₄-NO₂ (Fc-NO₂) (Fc= ferrocene) have been synthesized and characterized using micro-analyses, FTIR, ¹H and ¹³C NMR, UV-Vis and for Fc-NO₂ single crystal X-ray diffraction. The structural studies reveal that Fc-NO₂ possess an extensively conjugated system where C₅H₄(Cp)-CH=N-N=CH-p-C₆H₄-NO₂ is nearly planar which suggest strong electron communication from the ferrocene moiety to the p-C₆H₄-NO₂ group via a -CH=N-N=CH- spacer. Both compounds have been used as sensitizers in titanium oxid based dye-sensitized solar cells (DSSCs) which indicate that amongst both sensitizers the Fc-OH one exhibited a better cell performance with J_sc 12.91 mA·cm⁻², V_oc 0.710 V, η 5.88% and incident photon to a current conversion efficiency of 53%. Electron injection in the conduction band of the titanium oxide semiconductor have been authenticated with the help of density of states calculations.