Designing ferrocenyl thiophene chalcones as light harvester candidates for dye-sensitized solar cells

In dye-sensitized solar cells (DSSCs), the dye (or photosensitizer) plays a crucial role. It absorbs light and generates electrons, which affects the efficiency of converting sunlight into electricity. While Ru(II)-based dyes are common in DSSCs, their scarcity, susceptibility to degradation, and limited absorption range pose challenges for wider adoption. Three new ferrocenyl-thiophene compounds have been synthesized, all sharing the same core structure, but the distinctive difference is the existence of methyl group (CH₃) and bromine (Br) substituents attached to the thiophene ring. Using the structures obtained from spectroscopic and X-ray crystallography analyzes, the chemical reactivity of these compounds is theoretically evaluated. Cyclic voltammetry (CV) analysis and electrochemical impedance spectroscopy (EIS) were employed to investigate the redox properties and electron transport mechanisms of the material. The bromination process demonstrates its efficacy for dye applications, while the methyl attachment to the thiophene ring enhances anchoring toward TiO₂, contributing to improved performance in DSSCs. Overall, the compound featuring bromine exhibited a lower band gap compared to the others, resulting in higher efficiency in solar simulation analysis, nearly double that of the methyl-containing compound, and significantly surpassing the plain thiophene compound. EIS analysis revealed that, among the three ferrocenyl chalcone dyes, the bromine-containing compound exhibited the highest charge recombination resistance and longest electron lifetime.