Probing Interfacial Halogen-Bonding Effects with Halogenated Organic Dyes and a Lewis Base-Decorated Transition Metal-Based Redox Shuttle at a Metal Oxide Interface in Dye-Sensitized Solar Cells

Abstract

Metal-free bis-cyclopentadithiophene-based molecular sensitizers with varying halogens (Cl, Br, and I) installed at a terminal position in conjugation with the dye frontier molecular orbital π-system are studied in combination with two cobalt redox shuttles (RSs): with and without a nonmetal-coordinated nitrogen atom (pyrazine or pyridine) accessible to the halide-decorated dyes. This systematic study employs UV–vis absorption, cyclic voltammetry, density functional theory calculations, and nanosecond transient absorption spectroscopy to probe the influence of possible halogen-bonding between the dyes and the pyrazine-based RS on electron-transfer reactions and effects on dye-sensitized solar cell performances. The results of this study imply a possible halogen-bonding event occurring between the halogenated dyes and the halogen binding RS with substantial effects on electron-transfer reaction rates.