Theoretical Design of Alkaline‐Earth Metal‐Based Sensitizers for Dye‐Sensitized Solar Cells: A DFT/TDDFT Study of α/β Isomerism on Optoelectronic Properties

Integrating alkaline‐earth metals (Be, Mg, and Ca) into the donor of D–π–A organic dyes and systematically exploring α/β positional isomerism offers a novel sCE: * Madanihedidi(writing ‐ review & editing), * Hichammahdjoub–araibi(writing ‐ review & editing), * Mouradzouaoui‐rabah(conceptualization, investigation, methodology, software, formal analysis, visualization, validation, writing ‐ review & editing, writing ‐ original draft), not found in author list. Please review and add if required.trategy to tune dye‐sensitized solar cells. DFT/TD‐DFT calculations show that all designed dyes align appropriately with TiO 2 and the I − /I 3 − redox couple. β isomers exhibit stronger electron‐injection driving forces (ΔGinj down to −1.38 eV for D2β), while α isomers provide longer excited‐state lifetimes (up to 0.37 ns) and higher open‐circuit voltages (up to 0.79 V). The HOMO–LUMO gap narrows progressively (α: 2.46→1.88 eV; β: 2.58→1.83 eV), red‐shifting absorption and enhancing light harvesting. NBO and conceptual DFT analyses confirm efficient intramolecular charge transfer, with D2β showing the strongest electron‐exchange capability. D2α achieves the optimal photovoltaic balance among injection kinetics, lifetime, and voltage, emerging as the most promising sensitizer. These findings demonstrate that alkaline‐earth metals and their substitution position serve as powerful internal modulators for push–pull dyes, offering practical design guidelines for low‐cost metal‐based sensitizers. Experimental validation and dye–TiO 2 interface studies are needed to confirm the predicted performance, as the calculations consider isolated dyes without interfacial effects.