Precision Fluorine Functionalization in Alkyl Side\nChains of Polymer Donors for Highly Efficient Organic Solar Cells

Fluorination\nof polymer donors has demonstrated considerable potential\nfor boosting the performance of organic solar cells (OSCs). However,\nachieving optimal performance requires careful management of fluorine\nlevels, as excessive fluorination may adversely affect device efficiency.\nIn this study, we introduce a controlled number of fluorine atoms\ninto the alkyl side chains of polymer donors to optimize their temperature-dependent\naggregation and intermolecular interactions. Four polymers (PTF0,\nPTF1, PTF2, and PTF3) with reduced synthetic complexity and varying\nlevels of fluorine incorporation were synthesized, allowing precise\ncontrol over their optoelectronic properties. Notably, PTF1, featuring\na single fluorine atom, effectively tunes the energy levels and promotes\nbeneficial intermolecular interactions with the corresponding nonfullerene\nacceptor. Moreover, PTF1 demonstrates enhanced aggregation and crystallinity,\nleading to efficient charge generation and transport, resulting in\nbinary and ternary OSCs with PCEs of 13.0% and 18.6%, respectively.\nThis study suggests the potential of precise fluorine functionalization\nin polymer donors as a potent strategy for crafting highly efficient\nOSCs and provides valuable insights for designing next-generation\nOSC materials, paving the way for future advancements.