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

TL;DR

This paper investigates how metallic absorption and layer corrugation affect the optical extraction efficiency in OLEDs, revealing that corrugation can both enhance and hinder light output depending on cathode absorption properties.

Contribution

It provides a detailed analysis of metallic absorption effects and demonstrates that non-absorptive cathodes combined with corrugation significantly improve OLED efficiency.

Findings

Corrugation increases light extraction when cathodes are non-absorptive.

Metallic absorption reduces optical output, especially with corrugated layers.

Corrugated OLEDs with non-absorptive cathodes nearly double optical efficiency.

Abstract

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.