Analytical extraction of the recombination zone location in organic light-emitting diodes from emission pattern extrema

We present an analytical method for extracting the recombination zone location from emission patterns produced by organic LEDs (OLEDs). The method is based on derivation of the closed-form expressions for OLED-radiated power developed in previous work and formulation of the analytical relations between the emitter position and the pattern extrema. The results are confirmed to be in good agreement with reported optical measurements. The resultant formulae offer insight regarding the dominant physical processes in the device and can be utilized to assess or verify the location of the recombination zone, a very important parameter in the optimization process of OLED efficiency, from standard optical measurements, otherwise a very difficult task to achieve.