(Figure Presented) CoMoCat single-walled carbon nanotubes (SWNTs) treated with diazonium salts can be used to fabricate solution-processable field-effect transistors (FETs) with a full semiconductor device yield. By increasing the network thickness, the effective mobility of the devices can be raised to ∼10 cm2 V-1s-1 while keeping the on-off ratio higher than 5000. The removal of impurities is essential to achieve high-on-off-ratio devices. This approach is promising for preparation of SWNT inks for printing high-performance devices in flexible electronics.