To understand the effects of acceptors on morphology aging, photoelectric conversion evolution, and stability of PM6-based solar cells, multiple characterization techniques, including morphology, transient absorption, and electrical characterizations, were conducted to analyze the correlation among morphology aging, photoelectric conversion evolution, and performance degradation of devices. The results demonstrated that the morphology features of PM6:Y6 and PM6:PC 71 BM active layers would change with time due to their unstable bulk heterojunction structures. The unstable active layers determined the evolution of photoelectric conversion and the stability of the devices. Furthermore, morphology aging was responsible for the increase of charge recombination. Compared with PM6:PC 71 BM, more delocalized and localized polarons were generated in PM6:Y6 solar cells, and the increased probability of charge recombination with morphology aging was relatively smaller. Therefore, the PM6:Y6 device showed a higher efficiency and better stability than the PM6:PC 71 BM device.