Luminance Uniformity of Large-Area OLEDs With an Auxiliary Metal Electrode

One of the key issues of a large-area organic light-emitting diode (OLED) for flat panel lighting applications is to enhance the uniformity of light emission. In this work, we have investigated the effect of an auxiliary metal (chrome) electrode in association with a device configuration on the luminance uniformity of a large-area (15 times 15 cm²) white OLED. We demonstrate that the ratio between the effective horizontal resistance of anode (indium-tin-oxide (ITO) with the grid patterned metal electrode) and the vertical resistance of the OLED device is the critical factor to determine the luminance uniformity. Moreover, the luminance uniformity is shown to be a function of the current density and degraded with increasing current density. Namely, the OLED panel with the 200-mu m-wide metal lines exhibits the luminance uniformity as high as 90% at 200 mA and 85% at 500 mA.