Effects of metallic absorption and the corrugated layer on the optical extraction efficiency of organic light-emitting diodes.

The absorption of a metallic cathode in OLEDs is analyzed by using FDTD calculation. As the light propagates parallel to the layer, the intensity of E(z) polarization decreases rapidly. The intensity at 2.0 microm from the dipole is less than a quarter of that at 0.5 microm. The strong absorption by a cathode can be a critical factor when considering the increase of optical extraction by means of bending the optical layers. The calculation indicates that the corrugation of layers helps the guided light escape the guiding layer, but also increases the absorption into a metallic cathode. The final optical output power of the corrugated OLED can be smaller than that of the flat OLED. On the contrary, the corrugated structure with a non-absorptive cathode increases the optical extraction by nearly two times.