Optimizing Electronic and Photovoltaic Properties of D-π-A Organic Dyes for DSSCs Using Density Functional Theory.

This research utilizes density functional theory to investigate the ground and excited-state properties of a new series of organic dyes with D-π-A configurations (D1-D6) for their potential application in dye-sensitized solar cells. The study focuses on modifying these dyes using various functional groups as π-bridges to optimize their electronic properties and improve their efficiency as sensitizers in DSSCs. The frontier molecular orbitals (HOMO and LUMO) were analysed to evaluate electron transfer properties. The energy gaps, ranging from 2.449 to 2.6979 eV, indicate favourable electron injection capabilities. Further analysis included molecular electrostatic potential, electron localization function, and localized orbital locator for all dyes. The maximum absorption wavelengths were found to range from 272.98 nm to 624.76 nm, covering both the UV and visible spectra. A significant redshift was observed with the addition of electron-withdrawing groups to the D-π-A structures, contributing to enhanced light-harvesting capabilities. The results indicate that all dyes exhibit improved open-circuit photovoltage, enhanced light-harvesting efficiency, and higher electron injection when compared to the reference dye (Dye1). Additionally, parameters such as oxidation potential, free energy change, redox potentials, electron transfer, and dye regeneration showed promising values, pointing to excellent photovoltaic efficiency. Electron injection from the dyes into the conduction band of TiO₂, followed by efficient dye regeneration, was confirmed. The choice of the π-bridge group, in particular, plays a crucial role in optimizing dye performance. Based on the theoretical findings, all of the studied dyes demonstrate strong potential as effective photosensitizers for DSSCs applications.