Synthesis, Characterization and Application of Cobalt(ii), Nickel(ii) and Copper(ii) Complexes as Sensitizer Dye in Dssc with 4-cyanopyridine and Isothiocyanate Ligands

Dye-sensitized solar cells (DSSCs) have been studied extensively for their advantages over conventional p-n junction devices, such as low cost, less toxic manufacturing, easy scale-up, light weight, and potential use of flexible panels. The sensitizer dye is a basic component in a DSSC which plays an important role in injecting the photo excited electron from valence band of the dye molecule into the conduction band of the wide band gap semiconductor such as TiO₂. Though a lot of work has been done using Ru complex as sensitizer for an efficient solar cell, only few works have been reported on other transition metal complex as a sensitizer in DSSC. Moreover, among all the semiconductor oxides, TiO₂ is preferred because of its excellent physicochemical properties. In the present study, we have prepared three complexes of cobalt(II), nickel(II) and copper(II) by reacting the respective metal nitrates with 4-cyanopyridine and isothiocyanate ligands at room temperature in aqueous medium. The complexes were characterized by elemental, FTIR and UV-visible spectroscopy technique and the results indicate that these complexes have the potentiality for application as a sensitizer in DSSC. One prototype solar cells were fabricated using one of the the as synthesized complexes as the dye sensitizers on nanoporous TiO₂ thin film and the photovoltaic parameters of the cells were compared. For the fabrication of the cells, TiO₂ thin films were prepared using commercially available TiO₂ nano powder on a transparent conducting oxide (TCO) glass substrate.