Synthesis and characterization of cobalt (II) pincer complexes and their application as dyes in dye-sensitized solar cells

Abstract

A series of eight cobalt(II) pincer complexes were prepared by using NNN tridentate and NN bidentate pincer ligand systems. All the ligands and complexes were completely characterized using various spectroscopic techniques and analytical methods including single crystal X-ray analysis. Optimization of the molecular structures of all the compounds was done by B3LYP computational method and the HOMO-LUMO energy gaps of the compounds were calculated. The optical band-gaps of the cobalt complexes were determined by using electronic spectral data and the corresponding electrochemical gaps were obtained from cyclic voltammetry studies. All the cobalt (II) complexes were used as dyes in the dye-sensitized solar cell and the photovoltaic parameters of the constructed solar cells were investigated. Complex C7, comprising of bis(benzimidazole) system with an ethylene backbone exhibited highest power conversion efficiency among the tested compounds.