Electronic and Optical Properties of Chalcone-Based Metal-Free Dyes with Naphthalene and Triphenylamine Donors: A TD-DFT Study
Hassan A.
Abstract
This theoretical study demonstrates how donor substitution (Naphthalene vs. Triphenylamine) on cyanoacrylic acid as acceptor influences the optical absorption and charge transfer behavior of chalcone-based dyes, highlighting design strategies for improved dye-sensitized solar cells. Density functional theory (DFT) and time-dependent DFT (TD-DFT) at the B3LYP/6-311G (d,p) level were employed to optimize the geometries and analyze electronic and optical properties in DMF solvent using the IEFPCM model. The results show that both naphthalene dye (Ac 1) and triphenylamine dye (Ac 2) possess frontier molecular orbital (FMO) levels suitable for efficient electron injection into the TiO₂ conduction band and regeneration by the electrolyte. Ac 1 exhibited a higher absorption maximum (338 nm) due to extended conjugation in the naphthalene donor, while Ac 2 showed a narrower HOMO–LUMO gap (2.61 eV) and favorable HOMO alignment, supporting faster dye regeneration. Although Ac 1 benefits from stronger visible-light absorption, Ac 2 demonstrated better electronic coupling, which may enhance overall DSSC performance. Given their low fabrication cost, tunable molecular design, and compatibility with flexible substrates, such DSSCs hold great potential for practical applications in building-integrated photovoltaics and portable energy devices, offering a sustainable alternative to fossil-fuel-based energy sources.
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