Synthesis of ruthenium complexes as sensitizers for dye-sensitized solar cells

Abstract

Five ruthenium complexes, SS01-SS05, were synthesized. The physical and electronic properties were studied and the compounds were used as a critical part of a dye-sensitized solar cell. The complexes, which are dyes or photosensitizers, are used as mediator to convert light to electric power. In this study, one of the bipyridine ligand of the synthesized complexes was a derivative of 2,3-diphenylpyrazino[2,3-f][1,10]phenanthroline, which was to serve as the light-harvesting unit of the complexes. The SS01-SS05 bear different substituents at the para-position of the phenyl ring such as –H, –OMe, –NEt2, –Me, and –Br. The data obtained from 1H NMR and ATR-IR spectroscopy were used to identify the structure of the compounds. In studying electronic structure, cyclic voltammetry was used altogether with absorption spectra to calculate HOMO and LUMO electronic levels. Upon the study of photovoltaic characteristic of the cell staining with SS01-SS05, it was illustrated that the overall conversion efficiency of SS01-SS05 were 2.60, 3.04, 2.60, 2.50, and 1.06%, respectively, which were lower than the efficiency (5.07%) obtained from the cell staining with standard N719. These were the results from the lower current density of the cells staining with SS01-SS05, possibly due to poorer electron injection from SS01-SS05 onto the TiO2 surface, when compared to the standard N719.