Prediction of OLED Luminance Using Impedance Measurements

Luminance is the main feature indicating organic light-emitting diode (OLED) degradation; however, this requires delicate photometric measurements that are difficult and costly to realize
in situ
. In this article, an original luminance decay prediction method not requiring optical measurements will be presented. Analysis of the impedance revealed a strong correlation between the luminance and the time constant of the equivalent circuit. As a result, the time constant is chosen as the main feature to track OLED degradation, the evolution of which is linearly modeled over time at different stress levels using the design of experiments methodology. Simultaneously, a linear relationship between luminance degradation and the evolution of time constants, in terms of the thermal stress applied, enables prediction of the luminance degradation over time. This method is an accurate novel solution for luminance tracking in particular for data taken inside the experimental plan limits.