Abstract
Three small-molecule non-fullerene electron acceptors containing different numbers of fluorine atoms in their end groups were designed and synthesized. All three acceptors were found to exhibit relatively narrow band gaps with absorption profiles extending into the near-infrared region. The fluorinated analog exhibited enhanced light-harvesting capabilities, which led to improved short-circuit current densities. Moreover, fluorination improved the blend film morphology and led to desirable phase separation that facilitated exciton dissociation and charge transport. As a result of these advantages, organic solar cells based on the non-fullerene acceptors exhibited clearly improved short-circuit current densities and power conversion efficiencies compared with the device based on the non-fluorinated acceptor. These results suggest that fluorination can be an effective approach for the molecular design of non-fullerene acceptors with near-infrared absorption for organic solar cells.
Highlights
Bulk heterojunction organic solar cells (OSCs) are a promising technology for solar energy collection and have attracted much interest owing to their unique advantages for the fabrication of lightweight and flexible devices (Li et al, 2016b, 2017a, 2018a,b; Zhao et al, 2016; Zhang et al, 2017b, 2018; Cheng et al, 2018; Hou et al, 2018; Zhang, 2018)
To achieve high photovoltaic performance of OSCs based on novel non-fullerene acceptors (NFAs), much effort has been devoted to the use of advanced device structures and sophisticated film-processing
The results revealed that the fluorinated acceptors outperformed their non-fluorinated counterpart BT-IC
Summary
Bulk heterojunction organic solar cells (OSCs) are a promising technology for solar energy collection and have attracted much interest owing to their unique advantages for the fabrication of lightweight and flexible devices (Li et al, 2016b, 2017a, 2018a,b; Zhao et al, 2016; Zhang et al, 2017b, 2018; Cheng et al, 2018; Hou et al, 2018; Zhang, 2018). The combination of these advantages leads to improved film morphology with appropriate phase domains and larger interfacial areas, which facilitates exciton dissociation and charge transport and enhances the overall photovoltaic performance of OSCs. In this work, we designed and synthesized a series of nonfullerene electron acceptors (BT-IC, BT-F, and BT-2F) with different numbers of fluorine atoms on their end groups.
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