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 (J_sc) and fill factor (FF), however, the open-circuit voltage (V_oc) 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 J_sc or FF, but it does lead to an improved V_oc. By fluorinating the NFA and having more fluorine on the donor polymer, we obtain both a high J_sc and V_oc 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).

中文翻译：

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氟化对供体聚合物和非富勒烯受体的影响：氟越多，则越好

有机光伏器件中供体聚合物或非富勒烯受体（NFA）的氟化是提高器件效率的有效方法。尽管已经有许多关于供体聚合物氟化的研究，但很少报道同时包含氟化供体和氟化NFA的共混物。在这项研究中，我们使用两种供体聚合物（4'-FT-HTAZ和4'-FT-FTAZ）和两种NFA（ITIC-Th和ITIC-Th1）和不同量的氟（从2F到6F）来研究如何混合物中的氟化程度会影响器件性能。我们发现氟化NFA会导致更高的短路电流密度（J _sc）和填充系数（FF），但是开路电压（V _oc）降低是由于最低的最低未占据分子轨道（LUMO）水平。向施主聚合物中添加额外的氟不会对J _sc或FF产生较大影响，但确实会导致V _oc的提高。通过氟化NFA并使施主聚合物上的氟更多，我们同时获得了较高的J _sc和V _oc，在4'-FT-FTAZ：ITIC-Th1的情况下，功率转换效率超过10％，氟含量最高（6F）。