DFT Study of the Effect of Different Metals on Structures and Electronic Spectra of Some Organic-Metal Compounds as Sensitizing Dyes

Ruthenium polypyridine-derivative complexes are used in dye-sensitized solar cells (DSSC) as a light to current conversion sensitizer. In order to lower cost of the dye-sensitized solar cells, the normal transition metals were used to replace the noble metal ruthenium and some compounds [ML2] (M = Ru, Ni, Mn, Cu; L = 5'-methyl-2,2'-bipyridine-6-carboxylato, I = RuL2, II = NiL2, III = MnL2, IV = CuL2) were selected as the replacement. The geometries, electronic structures and optical absorption spectra of these compounds have been studied by using density functional theory (DFT) calculations at the B3P86/LANL2DZ level of theory. The maximum absorptions of complexes are found to be at 646 and 979 nm for compound III and 617 nm for compound IV. The lambda(max) band in complexes III and IV have a large re-shift when compared to the standard compound I. This means that the panchromatic response of compounds III and IV means renders it as a suitable sensitizer for solar energy conversion applications.