Ultrafast organic diodes with low turn-on voltage based on a junction between C-60 and WO3 are proposed. The high electron mobility of C-60 layers and the optimal work function of hexamethyldisilazane (HMDS)-treated WO3 layers together provide ideal diode characteristics including high rectification ratio and low turn-on voltage. Ultrahigh frequency (UHF) compatible rectifiers with a low voltage drop are demonstrated with the C-60/Wo(3) diodes.