A non-fullerene electron acceptor with a spirobifluorene core and four diketopyrrolopyrrole arms end capped by 4-fluorobenzene

In this paper, a non-fullerene electron acceptor , SF(DPPFB) 4 , which owns a spirobifluorene core and four diketopyrrolopyrrole (DPP) arms end capped by 4-fluorobenzene, is designed and synthesized for solution-processable organic solar cells (OSCs). SF(DPPFB) 4 shows similar absorption bands as those of its non-fluorinated parent compound, SF(DPPB) 4 . However, the terminal fluorine atoms reduce the energy levels of SF(DPPFB) 4 , especially, its lowest unoccupied molecular orbital level decreases by 0.04 eV than that of SF(DPPB) 4 , which enlarges the energy offset between the electron donor and acceptor, favorable for the dissociation of excitons in OSCs. Moreover, the fluorination improves the electron mobility of SF(DPPFB) 4 . Thus, the OSCs with poly(3-hexylthiophene) as the electron donor and SF(DPPFB) 4 as the electron acceptor can provide a maximum power conversion efficiency of 4.42%, with a lifted short-circuit current ( J sc ) of 8.48 mA cm −2 .