Synergistic effect of halogenation on molecular energy level and photovoltaic performance modulations of highly efficient small molecular materials

Synergistic effect of halogenation on molecular energy level and photovoltaic performance modulations of the small molecular materials was clarified for efficient small molecular solar cells. BDTTS-F-R showed a high degree of crystallinity, resulting in a strong aggregation and poor phase separation of its blend film with PC71BM. When introducing the chlorine and bromine atoms instead of fluorine atom, the crystallinity of this type of small molecules was decreased gradually. However, the BDTTS-Cl-R device exhibited a more balanced μh/μe ratio (1.35) and a more favorable morphology, giving rise to the highest PCE of 10.78%.325