Herein, two donors based on fluorine substituted isatin units (DI3T-1F, DI3T-2F) were compared with the mixture of PC71BM for thick-film small molecule solar cells. The devices based on DI3T-1F demonstrate balanced charge transportand less trap-assisted recombination, leading to higher PCE of 8.33% witha thickness ca.150 nm compared to DI3F-2F (PCE of 7.32% with thick film at ca. 160 nm) without additives, solvent or thermal annealing treatments. Both devices based on small molecule:fullerene blends demonstrate good tolerance to active layer thickness from 150 to 300 nm. Our results indicate that less fluorine atoms on donor units can optimize the charge transport, phase-segregated morphology in small molecule solar cells without the need for post-treatment.