<p>Electron donors and acceptors in the active layer of organic solar cells have a significant influence on the power conversion efficiency of the cells. Fluorination is one of the most commonly applied and effective halogenation methods in developing novel donors and acceptors. Herein, to investigate the effects of fluorination on the molecular properties and photovoltaic performance, we selected PBnDT-TAZ and DT<i>x</i>BT (<i>x</i> = 0F, 1F) as the D-π-A-π type donors, combined with PC₆₁BM as acceptor. The geometries, electronic structures, excitation properties, and electrostatic potentials (ESPs) of the donors and donor/PC₆₁BM complexes were investigated by quantum chemical calculations. The rate constants of electronic processes at heterojunction interfaces were also analyzed. The results indicate that the fluorination of the benzothiadiazole (BT), benzotriazole (TAZ), and thienyl segments generally decreases the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies of donor molecules. Meanwhile, the effects of fluorination on HOMO energies are more significant than the effects on LUMO energies. The fluorination of the TAZ and thienyl segments usually generate a blueshift, reduce absorbance, and significantly increase average ESP, whereas the fluorination of BT induces a slight redshift of absorbance. The results suggest that the fluorination of thienyl, BT, and TAZ enhances intermolecular interactions, increases exciton binding and charge transfer (CT) energy, reduces the transferred charges between donors and PC₆₁BM, increases local excited states, and decreases CT and hybrid excited states, as well as effectively suppressing charge recombination rates at donor–PC₆₁BM interfaces. The results of this work provide a theoretical basis for understanding how fluorination regulates the photovoltaic performance of electron donors.</p>