Fused-ring electron acceptors with a macrocyclic side chain†

Three fused-ring electron acceptors, MC8-4H, MC8-4F and MC8-4Cl, featuring a new type of macrocyclic side chain were synthesized and applied in organic solar cells. The chemical structure of MC8-4H was unambiguously determined using single crystal X-ray diffraction analysis. The single crystal structure of MC8-4H indicates that the compact macrocyclic alkyl chain stretches over the central fused-ring core unit and causes a slight bending of the backbone. Among these three acceptors, MC8-4F shows the highest electron mobility of 6.64 × 10⁻⁴ cm² V⁻¹ s⁻¹ and the best performance in solar cells. Cells based on MC8-4F and the donor L4 exhibited power conversion efficiencies up to 14.68%.