Significant Improvement in Light Harvesting Efficiency of Naphthalene Imide Derivative Dyes via Linker Engineering for p-type Dye-Sensitized Solar Cells

A set of carbazole–naphthalene imide dyes with various linkers (phenyl, thiophene, furan) was designed and theoretically examined. The electronic structures, absorbance characteristics, and free-energy parameters, including hole injection (ΔGinject), dye regeneration (ΔGreg), and charge recombination (ΔGCR), were calculated. The furan-linked dye-3 displayed the most equilibrated profile of the investigated dyes, integrating a red-shifted absorption spectrum with advantageous ΔGreg and ΔGCR values. These findings emphasize linker engineering as a viable design approach to enhance orbital alignment, increase light-harvesting efficiency, and mitigate recombination in p-DSSCs, while also indicating the necessity for subsequent experimental verification. All computations were implemented utilizing Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) with Gaussian 09 software. Geometries were optimized employing the conductor-like polarizable continuum model (C-PCM) with chlorobenzene as the solvent at the B3LYP/6-311G(d,p) theoretical level. Molecular orbitals, absorbance spectra, ionization potentials, electron affinities, reorganization energies, and thermodynamic driving forces (ΔGinject, ΔGreg, ΔGCR) were obtained from these computations to elucidate structure–property correlations related to p-DSSCs functionality.