Fluorine-engineered thienyl-fused non-fullerene acceptors based on as-indacene for high-performance organic solar cells: a DFT study.

The growing demand for sustainable energy has driven the development of high-performance organic solar cells (OSCs). In this work, a series of donor-π-acceptor molecules were designed using 1,1,6,6-tetramethyl-as-indacene as the donor, furan as the π-spacer, and thienyl-fused IC derivatives as acceptors. Structural tuning was achieved through positional fluorine substitution and variation of the thienyl unit. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to investigate electronic, optical, and photovoltaic properties. The designed molecules exhibit reduced HOMO-LUMO energy gaps (by ∼0.12 eV) relative to the reference, indicating enhanced charge-transfer characteristics. Fluorine substitution increases dipole moments, suggesting improved molecular stability. Additionally, strong absorption in the red region (780-820 nm) in chlorobenzene indicates enhanced light-harvesting ability. These findings demonstrate that fluorination and acceptor engineering effectively modulate optoelectronic properties, highlighting the potential of these materials for high-efficiency OSC applications.