Modeling OLED Luminance Decay Under Thermal, Constant and Cyclic Electrical Stress

Organic Light Emitting diodes (OLED) are lighting devices which are sensitive to a number of intrinsic and extrinsic stresses due to their organic nature. This paper proposes a study of the degradation of warm white, large area OLED panels under accelerated thermal and electrical stress as a tool to estimate their lifespan. The laboratory-induced stress reflects the usual on/off use of lighting in different conditions by applying not only constant, but also cyclic electrical current. The luminance decay path was modeled using linear and stretched exponential decay models, showing that luminance degradation has a linear path in more than 77% of cases. The relationship between the decay rate parameter of the selected model and the stress factors, as well as the quadratic term of current was then constructed using a multi-linear regression method. It was found that cycling reduces the degradation rate by allowing the intrinsic characteristics of OLEDs to recover. Finally, the Joule losses presented in the quadratic term of the current were proved to accelerate the degradation rate of OLEDs.