Degradation Mechanism Analysis for LED Phosphors under Hygrothermal Environment

This study selects yellow, red and orange phosphors used in high color rendering white packages, analyzes their luminescence and thermal properties, crystal structures and micro morphologies during both the high temperature and high moisture ageing test and the water immersion test, and finally figures out the degradation mechanisms of different phosphors. The results show that: 1) the hydrolysis reaction of phosphors under hygrothermal environment produces OH- and increases the environment's pH value, which can lower the crystallinity of phosphor hosts, increase the lattice vibration and light-induced heat, and enhance the thermal quenching effect of phosphors. Meanwhile, the surface roughening of phosphor particles can increase the blue light scattering and lower its absorption and conversion efficiency; 2) the degradation trends of both luminescence and thermal properties of phosphors under the water immersion test are similar to those under high temperature and high moisture ageing test. So it is an effective method to assess the reliability of LED phosphors under hygrothermal environment. © 2020, Science Press. All right reserved.