Isomeric Nonfullerene Acceptors: Planar Conformation Leading to a Higher Efficiency

Noncovalent conformational lock (NCL) is a beneficial noncovalent intramolecular interaction that assists in maintaining the molecular planar conformation. Such a planar conformation is favorable for a shorter molecular distance and higher molecular crystallinity, further yielding a more efficient charge transfer and higher power conversion efficiency (PCE). In this contribution, a pair of isomeric small-molecular nonfullerene acceptors (THP-4F and HPT-4F) were designed and synthesized based on the central core modification. HPT-4F with a negligible dihedral angle of 0.23 degrees showed a highly planar conformation, recombination, and enhanced Jsc and fill factor, leading to a PCE of 8.68%, nearly 8 times higher than 1.31% of its isomer THP-4F. This work gives a clear view of NCLs and molecular planarity for molecular design and efficient organic photovoltaic materials by comparing two structural isomers' totally different properties.

Automated summary

The importance of noncovalent conformational locks in molecular design and organic photovoltaic materials is studied. By comparing the properties of two structural isomers, it is found that molecules with highly planar conformations have higher power conversion efficiency.