Nonlinear Mixed Model and Reliability Prediction for OLED Luminance Degradation

In this study, we develop a nonlinear mixed modeling for the luminance degradation of flexible OLED, enabling precise lifetime prediction even with a limited data obtained from 48h of aging tests. A 4-parameter exponential model is employed, and its parameter is estimated by NLME (nonlinear mixed effect model)and NLS (nonlinear least square)method respectively. Considering time-dependent random behaviors of an emissive layer deterioration, NLME is better fitted to empirical data set than NLS and stretched exponential decay (SED), examined by the goodness-of-fit test. In fact, NLME method provides a precise lifetime prediction within $< 1{\%}$ of the mean absolute error percentage for the estimation of long-term reliability at 1,000h, which is benefit for technical feasibility judgement particularly with fast turnaround feedback in the earlier stage development.