Insights into Halogen Atom Effects on Donor–Acceptor Complexes in Organic Solar Cells: A Density Functional Theory Study on Quinoxylated Donors Family

This study explores the molecular structures and properties of quinoxaline-based donor materials complexed with highly efficient electron-acceptor molecules in organic solar cells. Employing density functional theory calculations, the interaction between PBQX (X = 5-F, 6-F, 5-Cl, 5-Br, 6-Cl, 6-Br) electron donors and two well-known electron acceptors (Y6 and BTP-4Br) is systematically analyzed. Variations in the halogen atoms of donor compounds are examined to assess their impact on the electronic structure of donor-acceptor complexes. Halogen atoms (F, Cl, Br) in quinoxylated donors influence weak interactions, crucial for charge transport. Since dipole moment and intermolecular electric field play a significant role in molecular packing and exciton separation, they are also studied, predicting the best performance of PBQ6-F compared to PBQ5-F. Generally transition density matrix, hole-electron analysis, and charge transfer states in complexes corroborate the better behavior of PBQ6-F over PBQ5-F. Finally, all these findings are reflected in the kinetic study, carried out through Marcus theory for the different donor-acceptor combinations analyzed in this work, which could have implications for future experimental studies. As demonstrated by systematic studies such as the present one, variations in halogen atoms shed light on to propose possible donor-acceptor combinations in organic solar cells.