Angular Dependence of the Emission from a Conjugated Polymer Light‐Emitting Diode: Implications for efficiency calculations

The ability to compare electroluminescence efficiencies is important now that light‐emitting diodes (LEDs) have been constructed using many different polymers and different device structures. Various ways of defining and measuring the efficiency of polymer LEDs are discussed, revealing the need to understand the nature and orgin of the angular dependence of the emission. A model for the angular distribution of the emitted light is proposed and measurements of the ligh output of a polymer LED described whose results are consitent with the model.