Tailoring the Electron‐Deficient Central Core on Fused‐Ring Nonfullerene Acceptors: Deciphering the Relationships Between Structure, Property, and Photovoltaic Performance

In the field of organic solar cells, organic semiconductors with Y6-based chemical structure and their corresponding quinoxaline-based assemblies are settled down as promising materials in the field of OSCs. However, the chemical structure of Y6 derivatives does not allow an expansion in the electron-withdrawing central core, in contrast to their quinoxaline-based analogues. For this reason, herein, two different quinoxaline-based A-D-A '-D-A derivatives with 2D pi-extended cores endowed with electroactive rylenimide moieties, named as Y6-1Napht and Y6-1Pery, are designed and synthesized. These enlarged fused-ring electron acceptors (FREAs) allow to study the influence of the length of the ryleneimide moiety on its structural, optical, electrochemical, and thermal properties as well as the tailoring of the frontier molecular orbitals. These results are also supported by quantum chemical calculations and photoluminescence measurements that provide additional information about their thermal stability and the microstructure of the films. Finally, as a proof of concept and to study the influence of these chemical modifications on the central core, solar cells based on these pi-conjugated nonfullerene acceptors are fabricated.