Efficient non-fused electron acceptor with C-shaped molecular geometry for photovoltaic application

Abstract

The geometrical configuration of non-fullerene acceptors (NFAs) is crucial for the photovoltaic performance of organic solar cells (OSCs). In this work, a novel non-fused electron acceptor, AC2, featuring a C-shaped geometry with a thiophene-thieno[3,2-b]thiophene central core, was designed and synthesized. Single crystal analysis and DFT calculations verified its three-dimensional (3D) interpenetrating network structure with a hexagonal ring pattern, which is similar to the widely reported Y6 derivatives. AC2 exhibits an optical bandgap of 1.37 eV and energy levels well-matched with wide-bandgap polymer donors. When blended with PBQx-TF to fabricate OSCs, the AC2-based device achieved a power conversion efficiency (PCE) of 14.21%, significantly higher than that of the control S-type non-fused ring acceptor A4T-16 (12.62%). This enhancement is attributed to the optimized molecular stacking pattern of the C-type geometry and reduced energy loss. This study highlights the impact of C-shaped geometry on the performance of OSCs, providing a new perspective for developing efficient and structurally simple electron acceptor materials.