Asymmetric nonfullerene acceptors with isomeric trifluorobenzene-substitution for high-performance organic solar cells

Asymmetric nonfullerene acceptors (NFAs) are an attractive candidate for high-performance organic solar cells (OSCs), whereas effective asymmetric strategies are highly needed to further advance their device performance. Herein, by alternating the substituted position of trifluorobenzene (Ar3F) in the terminal end group, two asymmetric NFA isomers, namely BTP-gamma-Ar3F and BTP-beta-Ar3F, are designed, and their photophysical and photovoltaic properties are fully compared. With the gamma-substituted fashion, it is shown that BTP-gamma-Ar3F features a better planarity, contributing to stronger crystallization and favorable phase separation with the PM6 donor polymer. As a result, a higher power conversion efficiency of 17.42% along with a high open circuit voltage of 0.90 V is realized in the PM6:BTP-gamma-Ar3F-based OSCs. The established structure-property relationship provides a rational design principle for asymmetric NFAs toward high photovoltaic performance.

Automated summary

By alternating the substituted position of trifluorobenzene (Ar3F) in the terminal end group, two asymmetric nonfullerene acceptor (NFA) isomers, namely BTP-gamma-Ar3F and BTP-beta-Ar3F, were designed and their photophysical and photovoltaic properties were compared. It was found that BTP-gamma-Ar3F exhibited better planarity, leading to stronger crystallization and favorable phase separation with the PM6 donor polymer, resulting in higher power conversion efficiency (17.42%) and open circuit voltage (0.90 V) in PM6:BTP-gamma-Ar3F-based organic solar cells. This established structure-property relationship provides a rational design principle for asymmetric NFAs towards high photovoltaic performance.