The normalized luminance L/Lo of an OLED is observed to decrease with respect to time as shown in Table 1. Determine the lifetime of this OLED and discuss briefly the causes of the luminance degradation in these devices. Table 1 L/Lo 1 (hr) 1 0.983 0.952 0.920 0.610 0.434 0.286 0.189 0 20 60 100 600 1000 1500 2000