Solid State Lighting Color Shift

Luminous flux maintenance and color stability are two important factors to evaluate the lighting quality. Where a significant amount of research efforts are performed on the former and even some standards have been generated for lumen decay acceleration, research activities and achievements on the latter are lagging behind. DOE Energy Star Program requires that the change of chromaticity over the minimum lumen maintenance test period (6000 hours) should be within 0.007 on the CIE 1976 (u', v') diagram. The color shift mechanisms for LED lighting are complex due to its comprehensive structure, generally composed of LED die, phosphor, silicone, reflector, diffusers, and so on, all of which may contribute to the color shift during operation. On top of this, each individual component has its own degradation mechanism. Studies on the LED based luminaire level color shift reliability are little publicly available except some based on the statistical (data-driven) method...