Isomerization Strategy of Nonfullerene Small-Molecule Acceptors for Organic Solar Cells

Nonfullerene acceptors (NFAs) are a current focus of research on bulk-heterojunction organic solar cells (OSCs), as they can exhibit strong absorption, suitably matched energy levels, and good stability. Isomerization affords a new material design strategy for nonfullerene small-molecule acceptors (SMAs). In this article, the development of isomeric nonfullerene SMAs, including isomeric perylene diimide (PDI)-based nonfullerene SMAs and isomeric acceptor-donor-acceptor (A-D-A)-type nonfullerene SMAs, is reviewed. The general design principles for isomeric SMAs and the key structure-property relationships are comprehensively surveyed and discussed. The remaining challenges and promising future directions of isomeric nonfullerene acceptors are presented.