It is shown that the viscosity of SWCNT inks is essential to produce highly homogeneous SWCNT films on the PET substrate with bar coating method. The Zn/Al complex-aided SWCNT ink has a viscosity threshold of 1.30 mPa s for the preparation of homogeneous films. The local flows of the film are suppressed above this viscosity, allowing homogeneous film formation. The Zn/Al complex dispersant can be easily removed from SWCNTs coated on PET by 1 M HNO3, giving a pure SWCNT film with the sheet resistance of 150 ohm/sq and transmittance of 90% at 550 nm immediately after HNO3 treatment. (C) 2016 Elsevier B.V. All rights reserved.