Three-dimensional (3D) non-fullerene small molecule acceptors with imide-linked perylene diimides (iPDI) on a 9,9′-spirobi[9H-fluorene] core were designed, synthesized and characterized for use in organic solar cells. The best power conversion efficiency of 5.31% is obtained using SF-iPDI2 in a solution-processed bulk heterojunction solar cell. These results demonstrate that PDI derivatives with 3D molecular structures could serve as high-performance electron acceptors in non-fullerene solar cells.