Computational design and performance investigation of novel benzo[1,2-b:4,5-b']difuran-4,8-dione-based organic dyes as sensitisers for dye-sensitised solar cells

A series of twelve organic dyes were theoretically investigated for use in dye-sensitised solar cells (DSSCs) in order to evaluate their structural, electronic, and optical properties in the gas phase. The calculations were performed using density functional theory (DFT) and its time-dependent (TD-DFT) at the B3LYP/6-31+G(d,p) level. The calculated parameters included the energies of the frontier molecular orbitals (FMOs), the energy gap, the maximum wavelength λmax, the excitation energy, the oscillator strength, the open-circuit voltage, the light-harvesting efficiency, the driving forces for injection and regeneration, and the excited-state lifetime. The results showed that introducing electron-donor and electron-acceptor groups linked by a difuran-type π-conjugated bridge significantly enhances the optical and electronic properties and increases the power conversion efficiency compared with the reference dye MBDFD. Among the investigated compounds, dyes M1 and M9 exhibited the most promising performance, particularly those containing a dimethylamino donor group linked through a difuran bridge, owing to their favorable electronic structure, strong light absorption, and efficient charge-transfer characteristics. These features indicate a superior capability for converting solar energy into electrical current. Overall, the results indicate that strategic modification of the donor and acceptor fragments critically determines the photovoltaic performance of the engineered dyes. Thus, the newly developed dyes, particularly M1 and M9, are promising candidates for the experimental synthesis and further development of high-performance dye-sensitized solar cells.