The operating voltage is reduced and luminous efficiency is improved in the organic light-emitting diodes (OLEDs) with UV-ozone treatment of molybdenum trioxide (MoO3) anode buffer layer. The interface of indium tin oxide (ITO)/MoO3 was investigated by X-ray photoelectron spectroscopy. It was found that the binding energies of Mo 3d, 0 1s, In 3d and C is were shifted to higher after UV-ozone treated MoO3. The enhanced properties are impervious to the UV-ozone treatment of ITO. Therefore, the improved performance can be attributed that the binding energies of Mo 3d, 0 is. In 3d and C 1s are changed to higher and also that the sheet resistance of ITO/MoO3 films is decreased after UV-ozone treated MoO3. (C) 2012 Published by Elsevier Ltd.