  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 Ez
polarization decreases rapidly. The intensity at 2.0 um from the dipole is less
than a quarter of that at 0.5 um. 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.
