Comparison of Two D−A Type Polymers with Each Being Fluorinated on D and A Unit for High Performance Solar Cells

For the purpose of investigating the effect of fluorination position on D−A type conjugated polymer on photophysical and photovoltaic properties, two types of fluorinated polymere are synthesized, HF with fluorination on electron‐donating unit and FH with fluorination on electron‐accepting unit. Compared to non‐fluorinated polymer, fluorinated polymers exhibit deeper HOMO energy levels without change of bandgap and stronger vibronic shoulder in UV−visible absorption, indicating that fluorination enhances intermolecular interaction. HF with fluorinated D unit exhibits well‐developed fibril network, low bimolecular recombination and high hole mobility, which lead a high PCE of 7.10% in conventional single‐junction solar cells, which is higher than the PCE (6.41%) of FH with fluorinated A unit. Therefore, this result demonstrates that fluorination on electron‐donating unit in D−A polymers could be a promising strategy for achieving high performance polymer solar cells. Two types of fluorinated D−A polymers with each being fluorinated on D and A unit are designed and synthesized. The D−A polymer with fluorinated D unit exhibits well‐developed fibril network, low bimolecular recombination and high hole mobility, leading to a high PCE of 7.10%, which is higher than the PCE (6.41%) of the polymer with fluorinated A unit.