Study of D–π–A coumarin bridge architectures for application as dyes in DSSC

Abstract

In this study, the molecular structures of twenty coumarin dyes were analyzed using first-principles calculations based on density functional theory. Geometry optimizations were performed for each molecular compound at the B3LYP/6-31G* and M06/cc-pVTZ levels of theory in gas phase. The electronic density, HOMO-LUMO energies, infrared spectrum, and chemical descriptors, such as electronegativity, chemical potential, and dipole moments, were examined from a combined theoretical-computational perspective. It was found that amine functional groups act as more effective electron donors than methyl groups, whereas the electron-accepting moiety must contain either carboxylic acid or cyano groups. Additionally, the presence of a dipole moment vector induces charge separation within the molecule, and molecular planarity influences electron delocalization. The dipole moment vector should originate from the coumarin bridge and extend toward the electron-donating group, establishing a charge transfer axis from the donor to the acceptor through the coumarin core.