The impact of fluorination on both donor polymer and non-fullerene acceptor: The more fluorine, the merrier
organic solar cells, non-fullerene acceptors, fluorination, bulk heterojunction
Fluorination of the donor polymer or non-fullerene acceptor (NFA) in an organic photovoltaic device is an effective method to improve device efficiency. Although there have been many studies on donor polymer fluorination, blends containing both a fluorinated donor and fluorinated NFA have rarely been reported. In this study, we use two donor polymers (4’-FT-HTAZ and 4’-FT-FTAZ) and two NFAs (ITIC-Th and ITIC-Th1) with different amounts of fluorine (from 2F to 6F) to investigate how the degree of fluorination in a blend impacts device performance. We find that fluorinating the NFA leads to a higher short-circuit current density (Jsc) and fill factor (FF), however, the open-circuit voltage (Voc) is decreased due to a depressed lowest unoccupied molecular orbital (LUMO) level. Adding additional fluorine to the donor polymer does not have a large effect on the Jsc or FF, but it does lead to an improved Voc. By fluorinating the NFA and having more fluorine on the donor polymer, we obtain both a high Jsc and Voc simultaneously, leading to a power conversion efficiency over 10% in the case of 4’-FT-FTAZ:ITIC-Th1, which has the most amount of fluorine (6F).
Tsinghua University Press
Nicole Bauer,Qianqian Zhang,Jeromy James Rech,Shuixing Dai,Zhengxing Peng,Harald Ade,Jiayu Wang,Xiaowei Zhan,Wei You, The impact of fluorination on both donor polymer and non-fullerene acceptor: The more fluorine, the merrier. NanoRes.2019, 12(9): 2400–2405