Gradient refractive index glass films for LED packaging

Because of the big refractive index difference between LED chip and encapsulant, a lot of photons generated in chip cannot escape out and finally convert to waste heat, which will rise the junction temperature and worsen the performances and reliability of LED devices. In this work, a glass film with gradient refractive index for LED packaging is proposed and its physical mechanism is studied. Glass powder is utilized to prepare light medium film and its RI can be adjusted by changing the mixture ratio of its component. Numerical and optical simulations are utilized to optimize the refractive index parameters and quantitative analysis. Structures with 2 to 3 optimal layers are demonstrated to be most effective and have the highest light extraction increase.