Currently, the power of modern LED chip for light is
above 1 W, even up to 5 W, and the area of chip is less than
1 mm2, corresponding to 100 W/cm2 of heat flux, which will result
in high chip junction temperature [1], and the high junction temperature will greatly lead to the dominant luminescence wavelength drift, the decline of the optical efficiency, as well as the
degradation lifetime of the phosphor