We designed and synthesized a series of fused-ring electron acceptors (FREAs) based on naphthalene-fused octacyclic cores end-capped by 3-(1,1-dicyanomethylene)-5,6-difluoro-1- indanone (NOICs) using a bottom-up approach. The NOIC series shares the same end groups and side chains, as well as similar fused-ring cores. The butterfly effects, arising from different methoxy positions in the starting materials, impact the design of the final FREAs, as well as their molecular packing, optical and electronic properties, charge transport, film morphology, and performance of organic solar cells. The binary-blend devices based on this NOIC series show power conversion efficiencies varying from 7.15% to 14.1%, due to the different intrinsic properties of the NOIC series, morphologies of blend films, and voltage losses of devices.