Asymmetric Dimerized Acceptor for Organic Solar Cells

Giant molecular acceptors (GMAs), such as dimer acceptors, are esteemed as materials for organic solar cells (OSCs); however, the limited miscibility with polymer donors poses a big challenge for achieving well-formed film morphology. Herein, for the first time, we employ an asymmetry design concept to create a new dimer 2BTP2F2Cl with asymmetric terminal groups as an efficient acceptor for OSCs. The asymmetric structure can well-manipulate the assembly behaviors within homomolecular 2BTP2F2Cl and heteromolecular interactions between donor and acceptor, producing a favorable morphology and charge dynamics. Remarkably, the device with 2BTP2F2Cl achieves an outstanding efficiency of 19.63%, which is a top-level value for the GMAs-based devices. Furthermore, due to the enhanced interaction further hindering the molecular diffusion, the 2BTP2F2Cl-based device displays improved stability compared to the symmetric dimer-based devices. Our work highlights the significance of the asymmetric GMAs for high-performance OSCs.