The fill factor (FF) of organic photovoltaic (OPV) devices has proven difficult to optimize by synthetic modification of the active layer materials. In this contribution, a series of small-molecule donors (SMDs) incorporating chalcogen atoms of increasing atomic number (Z), namely oxygen, sulfur, and selenium, into the side chains are synthesized and the relationship between the chalcogen Z and the FF of OPV devices is characterized. Larger Z chalcogen atoms are found to consistently enhance FF in bulk-heterojunction OPVs containing PC₆₁BM as the acceptor material. A significant ∼8% FF increase is obtained on moving from O to S to Se across three series of SMDs. The FF enhancement is found to result from the combination of more ordered morphology and decreased charge recombination in blend films for the high-Z-chalcogen SMDs. Because this FF enhancement is found within three series of SMDs, the overall strategy is promising for new SMD materials design.

中文翻译：

---

通过小分子光伏中硫族元素侧链操纵增强的填充因子

事实证明，有机光伏（OPV）器件的填充因子（FF）难以通过活性层材料的合成改性来优化。在此贡献中，合成了一系列小分子供体（SMD），其侧链上结合了原子序数（Z）增加的硫属元素原子，即氧，硫和硒，并且硫属元素Z与FF的FF之间的关系OPV设备的特点。发现较大的Z硫族元素原子可在包含PC _61的体相异质结OPV中持续增强FFBM作为受体材料。在三个系列的SMD中，从O到S到Se时，FF显着增加8％。发现FF增强是由于高Z-硫属元素SMD的混合膜中更有序的形态和降低的电荷复合的组合导致的。由于在三个系列的SMD中都发现了这种FF增强，因此整体策略对于新的SMD材料设计很有希望。