Effect of introducing H2O vapor on properties of RF sputter-grown ITO anode layer for OLEDs

We report the effects of introducing H2O vapor on the structural, surface, and electrical properties of radio-frequency (rf) sputtered indium tin oxide (ITO) anode layer for organic light-emitting diodes (OLEDs). By introducing H2O vapor during rf sputtering, we obtained an ITO anode film with lower resistivity, higher transmittance, and a smoother surface relative to the conventional rf-sputter-grown ITO anode even though it was grown at a substrate temperature of 200 degrees C. Secondary ion mass spectroscopy analysis clearly shows that OH content in the rf-sputter-grown ITO anode film was significantly increased by adding H2O vapor. In addition, the current density-voltage-luminance result of an OLED fabricated on an H2O-vapor-incorporated ITO anode showed a lower turn-on voltage and higher luminescence than those of OLEDs fabricated on the reference ITO anode. This suggests that the introduction of H2O vapor during rf sputtering is an effective technique employed to improve the ITO anode layer for both top- and bottom-emitting OLEDs. (c) 2008 The Electrochemical Society.