Accessing OLED emitter properties by radiation pattern analyses

The optical features of the internal dipole radiation have major impact on the emission pattern and overall device efficiency of organic light-emitting diodes (OLEDs). We provide some general directives on how the OLED layered stack should be designed in order to enable precise measurements of the active optical properties of the emissive material (namely internal electroluminescence spectrum, profile of the emission zone and dipole moment orientation) by radiation pattern analyses. We discuss a model layered system and deduce universal emitter positions most suitable for the determination of the particular OLED internal features of interest. Furthermore, we evaluate the real benefit of conducting radiation pattern analyses utilizing a substrate index-matched glass-hemisphere.