General optical metrology for the dipole orientation in organic light-emitting diodes

Considerable progress has been made in organic light-emitting diodes (OLEDs) to achieve high external quantum efficiency (EQE), among which the dipole orientation of OLED emitters has a remarkable effect. In most cases, EQE of the OLED emitter is theoretically predicted with only one orientation factor to match with corresponding experiments. Here, we develop a distribution theory with three independent parameters to fully describe the relationship between dipole orientations and power densities. Furthermore, we propose an optimal experiment configuration for measuring such distribution parameters. Measuring the unpolarized spectrum extremely can dig more information of dipole orientation distributions with a rather simple way. Our theory provides a universal plot of the OLED dipole orientation, paving the way for designing more complicated OLED structures.