Homoleptic d10 metal complexes containing ferrocenyl functionalized dithiocarbamates as sensitizers for TiO2 based dye-sensitized solar cells

Four synthesized d(10) metal complexes, namely, ferrocenyl based pyridyl functionalized dithiocarbamates macrocyclic metal-organic coordination polymers, [M(L)(2)](infinity) (M = Zn(II), L = (N-ferrocenyl-methyl-N-pyridin-4-ylmethyl)dithiocarbamate Zn-2; Cd (II), L = (N-ferrocenyl-methyl-N-pyridin-3-ylmethyl) dithiocarbamate Cd-3 and dimers [M(L)(2)](2) (M = Zn(II), Hg(II), L = (N-ferrocenyl-methyl-N-pyridin-3-ylmethyl) dithiocarbamate, Zn-1 and Hg-4 were studied for their sensitization activities when anchored on TiO2 thin film electrode and employed as photoanode in dye-sensitized solar cells (DSSC). The absorption spectra of test dyes in dichloromethane solution indicated absorption in 400-500 nm range for all complexes, revealing the possibility of their use as photosensitizers for TiO2. The cyclic voltammetry (CV) demonstrated quasi-reversible behavior for all the complexes. All the dye sensitizers showed significant light harvesting properties with an exceptionally high light-to-electrical energy conversion efficiency (6.23%) shown by Zn-1 complex which was close to that obtained with standard Ru dye, N719 (6.96%) under similar experimental conditions. The better performance of Zn-1 complex compared to other studied dye sensitizers were attributed to its structural features. The extent of interfacial charge recombination and electron lifetime were evaluated by the electrochemical impedance spectroscopy (EIS).