High-performance n-type organic field-effect transistors were developed with ionic-liquid gates and N,N′′-bis(n-alkyl)-(1,7 and 1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide)s single-crystals. Transport measurements show that these devices reproducibly operate in ambient atmosphere with negligible gate threshold voltage and mobility values as high as 5.0 cm2/V s. These mobility values are essentially identical to those measured in the same devices without the ionic liquid, using vacuum or air as the gate dielectric. Our results indicate that the ionic-liquid and n-type organic semiconductor interfaces are suitable to realize high-quality n-type organic transistors operating at small gate voltage, without sacrificing electron mobility.