Recently, Professor Xiaowei Zhan’s group from College of Engineering at Peking University made new progress in nonfullerene acceptors for organic solar cells (OSCs). They developed a new fluorinated fused-ring electron acceptor (FREA) with 3D stacking and exciton and charge transport (Adv. Mater., DOI: 10.1002/adma.202000645).
In 2015, the Zhan group pioneered the concept of FREA and invented the landmark molecule ITIC (Adv. Mater., 2015, 27, 1170–1174, cited 1590 times). In 2017, they firstly introduced fluorinated 2-(3-oxo-2,3-dihydroinden-1-ylidene) -malononitrile, 1FIC and 2FIC, in FREAs (J. Am. Chem. Soc., 2017, 139, 1336–1343, cited 547 times; Adv. Mater., 2017, 29, 1700144, cited 549 times). Now, all the best nonfullerene acceptors are based on 1FIC/2FIC.
Most recently, they proposed a new design strategy to construct FREAs via fluorination of both end-groups and side-chains. Close 3D stacking network is formed due to 3D non-covalent interactions caused by F atoms on both end-groups and side-chains, which is beneficial to efficient 3D exciton and charge transport. The OSCs based on FINIC with fluorinated end-groups and side-chains show an efficiency of 14.0%, much higher than that of the nonfluorinated INIC-based cells (5.1%).
The research work was supported by the National Nature Science Foundation of China and Basic Research Promotion Project of Peking University.
The molecular structures and device performance (Credit: Xiaowei Zhan)