Optimizing side chains on different nitrogen aromatic rings achieving 17% efficiency for organic photovoltaics

Abstract

Balancing charge generation and low energy loss (Eloss), especially in the wide spectral absorption region is critical to obtain high-performance organic photovoltaics (OPVs). Therefore, Y11-M and Y11-EB are designed and synthesized through modifying alkyl chains on different nitrogen aromatic rings of the reported non-fullerene acceptor Y11. Although all the molecules have almost similar low band-gap (around 1.30 eV), Y11-M and Y11-EB exhibit wider absorption in 410–870 nm region. Eventually, the conventional devices based on Y11-M and Y11-EB possess more efficient charge generation with low Eloss (around 0.44 eV). In addition, outstanding efficiencies of 16.64% and 17.15% with the fill factor of 76.15% and 74.73% are obtained in PM6:Y11-M and PM6:Y11-EB-based devices, both higher than Y11:PM6. The results highlight the importance of rational alkyl chains optimization, and a good structure-property relationship is established as well.