Effect of thermal stress and short-wavelength visible radiation on phosphor-embedded LED encapsulant degradation

This study evaluated the effects of short-wavelength radiation and thermal stress leading to thermal degradation of an LED encapsulant, which contributes to reduced light output. The effect of light transmission was measured in encapsulant samples with different YAG:Ce phosphor concentrations mixed in epoxy, which were subjected to short-wavelength optical radiation and thermal stress. Encapsulant samples with increasing phosphor concentrations showed lower degradation rates of the encapsulant under thermal stress, while under short-wavelength optical radiation the samples with phosphor showed higher degradation rates. (C) 2015 Elsevier B.V. All rights reserved.