Efficient Top-Emitting Organic Light Emitting Diode with Surface Modified Silver Anode

The enhancement of quantum efficiency using a suface modified Ag anode in top-emitting organic light emitting diodes (TEOLEDs) is reported. The operation voltage at the current density of 1 mA/cm 2 of TEOLEDs decreased from 9.3 V to 4.3 V as the surface of anode coated with CuOx layer. The work function of these structures were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra revealed that the work function of the Ag/CuOx structure is higher by 0.6 eV than that of Ag. Thus, the CuOx structure acts as a role in reducing the hole injection barrier by about 0.6 eV, resulting in a decrease of the turn-on voltage of top-emitting light emitting diodes.