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In organic solar cells (OSCs), it is an effective way to improve the power conversion efficiency (PCE) by adding a guest component with appropriate absorption and energy levels in the host system. Herein, a new nonfullerene acceptor (NFA) named TBF-2Cl was developed by the strategy of expanding the π conjugated core of 2,2’-(((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b’]dithiophene-2,7-diyl)bis(methaneylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDT-4Cl) with two benzene rings. With increase of benzene units, TBF-2Cl exhibits higher lowest unoccupied molecular orbital (LUMO) level of −3.75 eV than that of one benzene unit based NFA IDT-4Cl and fluorene core based NFA F-2Cl, which facilitates enhancing the open-circuit voltage (Voc) of ternary devices. Moreover, TBF-2Cl film shows a medium optical bandgap with the absorption range from 500–800 nm, being well complementary with the wide bandgap polymer donor D18 and narrow bandgap NFA CH-6F. Accordingly, a remarkable PCE of 18.92% with a high short-circuit current density (Jsc) of 27.40 mA·cm−2, a fill factor (FF) of 0.749, especially an outstanding Voc of 0.922 V was achieved for the optimal ternary device based on D18:TBF-2Cl:CH-6F, surpassing the binary counterpart (17.08%). The findings provide insight into the development of new guest acceptors for obtaining more efficient OSCs.
This work was financially supported by the National Natural Science Foundation of China (No. 52173010) and Jining University (Nos. 2022HHKJ11 and 2019BSZX01).