  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%.
