We demonstrate an inverted top-emitting organic light-emitting diode using a transparent silver oxide (AgOx) anode formed by oxygen plasma treatment. The turn-on voltage decreased from 22 to 12 V, and the luminance increased from 175 to 630 cd/m(2) at 150 mA/cm(2) as the Ag anode was treated by O-2 plasma. The measurement of synchrotron radiation photoelectron spectroscopy and ultraviolet photoelectron spectroscopy revealed that the Ag changed AgOx and the work function was increased by 0.45 eV during O2 plasma treatment. The AgOx lowered the injection barrier for holes, enhancing the electroluminescent properties. (c) 2007 The Electrochemical Society.