Great attention has been paid to developing low bandgap non-fullerene acceptors (NFAs) for matching wide bandgap donor polymers to increase the photocurrent and therefore the power conversion efficiencies (PCEs) of NFA organic solar cells, while pyrene-core based acceptor–donor–acceptor (A–D–A) NFAs have been mainly reported via the 2,9-position connection due to their bisthieno[3′,2′-b']thienyl[a,h]pyrene fused via a five-membered ring bridge at the ortho-position of pyrene as the representative one named FPIC5, which has prohibited further narrowing their energy gap. Herein, an acceptor FPIC6 was exploited by creating the 1,8-position connection through fusing as bisthieno[3′,2′-b′]thienyl[f-g,m-n]pyrene linked at the bay-position via a six-membered bridge, with enhanced push–pull characteristics within such A–D–A structure. As a structural isomer of FPIC5, FPIC6 exhibited a much lower bandgap of 1.42 eV (1.63 eV for FPIC5). Therefore, the photocurrent and PCE of PTB7-Th:FPIC6 cells were improved to 21.50 mA cm⁻² and 11.55%, respectively, due to the balanced mobilities, better photoluminescence quenching efficiency and optimized morphology, which are both ∼40% better than those of PTB7-Th:FPIC5 cells. Our results clearly proved that a pyrene fused core with 1,8-position connection with electron-withdrawing end groups instead of 2,9-position connection is an efficient molecular design strategy to narrow the optical bandgap and improve the photovoltaic performance of NFA based OSCs.

中文翻译：

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连接性在基于聚py的非富勒烯受体向高效有机太阳能电池的显着带隙变窄中的作用

开发低能隙非富勒烯受体（NFA）以匹配宽带隙供体聚合物以增加NFA有机太阳能电池的光电流并因此增加其功率转换效率（PCE）的过程已经引起了广泛关注，而以pyr核为基础的受体-给体-受体（AD–A）NFA主要通过2,9-位连接得到报道，这是由于它们的双联[3'，2'- b ']噻吩并[ a，h ] re是通过五元环桥稠合的以of的邻位为代表的命名为FPIC5的FPIC5禁止进一步缩小其能隙。在此，接受者为FPIC6通过熔合作为bisthieno [3'，2'-通过创建1,8-位置连接被利用b ']噻吩基[ FG，MN ]芘在托架位连接经由一个六元桥，具有增强的推挽这种A–D–A结构中的特征。如的结构异构体FPIC5，FPIC6表现出1.42伏特（eV的1.63为低得多的带隙FPIC5）。因此，PTB7-Th：FPIC6电池的光电流和PCE提高到21.50mA cm ^-2。由于平衡的迁移率，更好的光致发光猝灭效率和优化的形态，它们分别比PTB7-Th：FPIC5细胞高约40％和11.55％。我们的结果清楚地证明，具有1,8位连接的吸电子端基而不是2,9位连接的pyr稠核是一种有效的分子设计策略，可缩小光学带隙并改善基于NFA的OSC的光伏性能。