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 .
Guojian Tian,Shengyun Cai,Xin Li,Hans Ågren,Qiaochun Wang,Jinhai Huang,Jianhua Su
Two new D–A–π–A configuration metal-free organic sensitizers (T1–T2) based on 5,7-dihexyl-6,12-diphenyl-5,7-dihydroindolo[2,3-b]carbazole and a DPP unit with a bulky branched alkyl chain have been synthesized for dye-sensitized solar cells. Due to a bulky branched alkyl chain being attached to the donor and DPP unit, both compounds obtain high Voc values. Under standard global AM 1.5 solar light conditions, the T1 based-device gives a high conversion efficiency of 8.24% with a Jsc of 15.72 mA cm−2, a Voc of 0.74 V and a FF of 0.71. These excellent performances make the donor dihydroindolo[2,3-b] carbazole and DPP unit promising candidates for further application in DSCs.
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