Fused Nonacyclic Electron Acceptors for Efficient Polymer Solar Cells
2017
Dai, Shuixing | Zhao, Fuwen | Zhang, Qianqian | Lau, Tsz-Ki | Li, Tengfei | Liu, Kuan | Ling, Qidan | Wang, Chunru | Lu, Xinhui | You, Wei | Zhan, Xiaowei
We design and synthesize four fused-ring electron acceptors based on 6,6,12,12-tetrakis(4-hexylphenyl)-indacenobis(dithieno[3,2-b;2′,3′-d]thiophene) as the electron-rich unit and 1,1-dicyanomethylene-3-indanones with 0–2 fluorine substituents as the electron-deficient units. These four molecules exhibit broad (550–850 nm) and strong absorption with high extinction coefficients of (2.1–2.5) × 10⁵ M–¹ cm–¹. Fluorine substitution downshifts the LUMO energy level, red-shifts the absorption spectrum, and enhances electron mobility. The polymer solar cells based on the fluorinated electron acceptors exhibit power conversion efficiencies as high as 11.5%, much higher than that of their nonfluorinated counterpart (7.7%). We investigate the effects of the fluorine atom number and position on electronic properties, charge transport, film morphology, and photovoltaic properties.
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