Abstract
We present a comprehensive model to analyze, quantitatively, and predict the process of degradation of organic light-emitting diodes (OLEDs) considering all possible degradation mechanisms, i.e., polaron, exciton, exciton-polaron interactions, exciton-exciton interactions, and a newly proposed impurity effect. The loss of efficiency during degradation is presented as a function of quencher density, the density and generation mechanisms of which were extracted using a voltage rise model. The comprehensive model was applied to stable blue phosphorescent OLEDs (PhOLEDs), and the results showed that the model described the voltage rise and external quantum efficiency (EQE) loss very well, and that the quenchers in emitting layer (EML) were mainly generated by dopant polarons. Quencher formation was confirmed from a mass spectrometry. The polaron density per dopant molecule in EML was reduced by controlling the emitter doping ratio, resulting in the highest reported LT50 of 431 hours at an initial brightness of 500 cd/m2 with CIEy<0.25 and high external quantum efficiency (EQE) >18%.
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