Surface treatment of molybdenum oxide for performance improvement of organic light emitting diodes

The molybdenum oxide (MoO3) thin layers are used as the hole injection layer in the organic light emitting diodes (OLEDs). The surface treatment of MoO3 with ultraviolet ozone (UVO), nitrogen (N-2) and argon (Ar) gas plasma have been studied. The turn on voltage is lowered in UVO treated device whereas for plasma treated device the turn on voltage increases. The surface roughness as well as the interface resistance increases with all the treatments. The UVO treated MoO3 device performance and stability enhances; the luminous efficiency by 16% and power efficiency by 14% compared with the reference device. The performance improvement can be explained by the change in work function of MoO3 with UVO treatment. (C) 2010 Elsevier B.V. All rights reserved.