Anchoring Group Engineering in Coumarin-Benzothiazole Sensitizers: A First-Principles Perspective for DSSCs

This study explores the potential of six novel metal-free organic dyes with a D-$\pi$-A architecture for use in dye-sensitized solar cells (DSSCs). All dyes share a common diethylamino coumarin donor and benzothiazole $\pi$-spacer, but differ in their acceptor/anchoring groups: acetic acid (A1), benzoic acid (A2), 2-cyanoacrylic acid (A3), rhodanine-3-acetic acid (A4), (chlorotetrahydroquinolinyl)cyanoacrylic acid (A5), and (oxotetrahydroquinolinyl)cyanoacrylic acid (A6). Using density functional theory (DFT) and time-dependent DFT (TD-DFT) with the B3LYP-D3 functional and 6-31G(d,p) basis set, we investigated the dyes' photophysical and photoelectrochemical properties. The investigation focused on tailoring the molecular structure to enhance acceptor strength and evaluating the ease of adsorption onto TiO$_2$. Geometric, structural, electrical, and optical properties, along with charge transfer processes, have analyzed using quantum chemical methods. The results suggest that these dyes are promising candidates for optoelectronic device applications.