Chalcogen-Induced Modulation of Optoelectronic Properties in Tetrahydroquinoline Dyes: Computational Insights for Dye-Sensitized Solar Cells

Abstract Chalcogen substitution provides a powerful strategy for tuning the optoelectronic properties of organic sensitizers. Here, Here, twelve tetrahydroquinoline (THQ) based dyes belonging to three parent series (THQ1, THQ2, and THQ3) and incorporating O, S, Se, and Te were systematically investigated using DFT (B3LYP/6-31G(d,p)) and TD-DFT (CAM-B3LYP/6-31G(d,p)) frameworks. Absorption maxima exhibit a red-shift from 459 nm (O) to 540 nm (Te), accompanied by high oscillator strengths and near-unity light-harvesting efficiencies. Emission extends from 564 to 767 nm, with excited-state lifetimes increasing up to 3.06 ns. Energy alignment reveals favourable electron injection and dye regeneration. Selenium and tellurium derivatives provide the optimal balance between spectral broadening and charge-transfer energetics, establishing design principles for next-generation DSSC sensitizers. The systematic comparison across the chalcogen series provides molecular-level insights and design principles for next-generation sensitizers with tunable optoelectronic performance.