Nonfullerene Acceptors Based on Naphthalene Substituted Thieno[3,2- B ]thiophene Core for Efficient Organic Solar Cells

Two nonfullerene acceptors (NFAs) TT-2FIC and DTP-2FIC were developed by using naphthalene substituted thieno[3,2-b]thiophene as the core, alkylthiophene, alkylthieno[3,2-b]thiophene or 4-alkyl-4H-dithieno[3,2-b:2′,3′-d]pyrrole as the π-bridges. This core could endow NFAs with coplanar backbone and twisted conjugated sidechains. In this way, over-aggregation of NFAs was suppressed, and TT-2FIC and DTP-2FIC exhibited good solubility and optimal π-π stacking. Eventually, PBDB-T:TT-2FIC and PBDB-T:DTP-2FIC cells achieved decent PCE of 4.25