Optical Enhancement in Heteroleptic Ru(II) Polypyridyl Complexes Using Electron-Donor Ancillary Ligands

Organic dyes are a viable alternative to silicon for energy conversion. Using simulations from first-principles, we show that chemical manipulation is a powerful tool for tuning the optical absorption spectra of a special class of dyes in a way that is convenient for exploitation in dye-sensitized solar cells. Specifically, we have carried out density functional theory calculations on three Ru(II) polypyridyl complexes with electron-donor ancillary ligands. These complexes were recently developed to study how different electron-donor ancillary ligands affect the photophysical and electrochemical properties of these dyes for light harvesting and photon-to-electron conversion efficiency. We found that the electron-donor ancillary ligands significantly enhance the light harvesting in the visible and the near-infrared regions relative to the reference dye N3. Furthermore, we detected a decrease in the ionization potential, which improves the energy alignment with the redox potentials of the electrolyte. These findings demonstrated that better organic materials for energy applications were developed. © 2014 American Chemical Society.