Synergistic Modifications of Side Chains and End Groups in Small Molecular Acceptors for High Efficient Non‐Fullerene Organic Solar Cells

Two new acceptor‐donor‐acceptor (A‐D‐A) type non‐fullerene acceptors, O‐NTIC and O‐NTNC, using hexacyclic naphthalene (cyclopentadithiophene) (NT) as the electron‐donating unit, and dicycanovinylindan‐1‐one (INCN) or phenyl‐fused dicycanovinylindan‐1‐one (NINCN) as the electron‐deficient unit, respectively, are synthesized. From the perspective of synthesis easiness and cost, para‐alkoxy‐phenyl is used as side chains of the NT core. It is worth noting that the introduction of para‐alkoxy‐phenyl unit could tune the molecular energy levels and lift the open‐circuit voltage (Voc). Compared with O‐NTIC, the introduction of extended end‐groups NINCN leads to a more ordered packing structure, much red‐shifted absorption and enhanced electron mobility of O‐NTNC. With polymer PBDB‐T as the donor, the organic solar cell (OSC) devices obtain a decent power conversion efficiency (PCE) of 9.1% for O‐NTIC and much improved PCE of 11.0% for O‐NTNC, respectively. Moreover, with a polythiophene derivative named PDCBT as the donor material, the PDCBT:O‐NTNC based device exhibits a PCE of 10.0%, among the highest PCEs for PDCBT devices. These results indicate that O‐NTNC has great potential on the application for high performance and low‐cost OSCs, and the extended end group NINCN as well as para‐alkoxy‐phenyl side chain substituted core could be promising units for the design of materials with high performance. A new high efficiency small molecular acceptor O‐NTNC is designed and synthesized, by introducing para‐alkoxy‐phenyl side chain and new developed end group named phenyl‐fused dicycanovinylindan‐1‐one (NINCN). The binary solar cell devices based on O‐NTNC exhibits 11.0% with PBDB‐T and 10.0% with a polythiophene derivative named PDCBT as donor, respectively.