Degradation behavior of GaN-based LEDs encapsulated with different phosphors

The degradation behaviors of GaN-based LEDs encapsulated with different phosphors were studied. The results of the aging experiments show that the yellow phosphor is the most stable phosphor, although the green and red phosphors can help to improve the color quality, they strongly influence the reliability. Comparing the accelerating factors, such as the aging temperature and relatively humidity, although the aging temperature 25 °C is less than 55 °C, but because of a higher relative humidity, the luminous flux and color temperature of white LEDs were still strongly influenced, especially for the phosphors. The optical power and luminous flux of blue LEDs, LEDs with yellow phosphor and LEDs with the yellow/red mixed phosphors aged at 25 °C (RH 21%) and 55 °C (RH 10%) increased during the first 400 hours and then decreased after that, but LEDs with green/red mixed phosphors decreased continually with the aging time.