Influence of Substituent Groups on Chemical Reactivity Kinetics of Non-Fullerene Acceptors

Substitution (such as fluorine substitution, F-) of terminal groups or atoms in non-fullerene acceptors (NFAs) is an effective strategy to tune the optoelectronic properties of non-fullerene electron acceptors and enhance their photovoltaic performance. But, how the substitution influences chemically reactivity or stability has not been reported. Here, we report that the terminal fluorine-substitution would increase the chemical reactivity. This is supported by three different evidences: Frist, device with fluorine-substituted NFA shows more severe “S” shape in the current density-voltage (J-V) characteristics under illumination when polyethylenimine is used as the interfacial layer and larger efficiency difference comparing with the reference device with ZnO as interfacial layer. Second, the fluorine-substituted NFA shows higher reaction rate with monoethanolamine model compound, monitored by nuclear magnetic resonance (NMR) spectroscopy. Third, mass spectrometry on the products of the NFAs added with mo...