Towards a generic OLED lifetime model

The limitations of t1/2 lifetime testing for OLED displays are discussed in the context of permanent and recoverable luminance decay. Different pixel drive schemes, operating temperature, and schemes of gray-level generation are all found to be important in determining the operational lifetime where both permanent and recoverable contributions to the luminance decay exist. In addi- tion, the importance of assessing lifetime with respect to a particular usage model is introduced and a method of lifetime characterization is devised to account for all of the factors discussed. The method measures luminance degradation over a series of operating cycles where the stress factors on the display are randomly generated for each cycle. The luminance degradation is then analyzed with linear regression, and the regression fit coefficients give an understanding of the degradation in dif- ferent usage models so that an assessment of the display’s suitability for a particular application can be made.