We firstly proposed the concept of "fused-ring electron acceptor FREA)",and designed and synthesized a series of FREAs.These FREAs present some advantages: l) They have high electron mobilities similar to those of fullerenes;2) They exhibit strong and broad absorption,especially in the 700-800 nm range,and can match with wide-bandgap donor polymers to achieve complementary absorption;3) They have tunable energy levels and thus match with various high-performance electron donors;4) Their solubility,crystallinity and film morphology can be tailored;5) Their synthesis is easy to scale up.Organic solar cells (OSCs) based on these FREAs exhibited power conversion efficiencies of >11%,which is a new record for fullerene-free OSCs.