Influence of hydroxyl functionalization on the electronic properties and thermoelectric–photovoltaic performance of anthracene-based d–π–a systems

A systematic theoretical investigation is presented to elucidate the influence of progressive hydroxyl substitution on the optoelectronic, photovoltaic, and charge-transport properties of anthracene-based donor–π–acceptor dyes. Five metal-free dyes were designed and analyzed using density functional theory (DFT), time-dependent DFT (TD-DFT), and charge-transport simulations. The results demonstrate that hydroxyl functionalization effectively modulates the electronic structure by elevating the HOMO energy, narrowing the HOMO–LUMO gap, and enhancing intramolecular charge-transfer character. These effects lead to red-shifted absorption spectra, increased oscillator strengths, and improved light-harvesting efficiency. Key dye-sensitized solar cell (DSSC) parameters, including electron-injection driving force, regeneration feasibility, and open-circuit voltage trends, were systematically evaluated and benchmarked against standard sensitizers. Dyes with moderate hydroxyl substitution exhibit the most favorable balance between optical absorption enhancement and electron-injection energetics. In addition, donor functionalization improves frontier-orbital alignment and electronic coupling in molecular junctions, resulting in enhanced charge-transport and thermoelectric performance. Overall, this study provides clear structure–property relationships and highlights hydroxyl substitution as an effective donor-engineering strategy for the rational design of high-performance anthracene-based dyes for DSSC and nano-optoelectronic applications.