The light-emitting diode lighting (LED) encapsulant is an indispensable part of the LED devices

and it protects the LED chip from the damage of the environmental temperature

humidity

radiation

mechanical forces and so on. So far

the silicone based LED encapsulants considered as an ideal kind of material for high-power LED encapsulation. They show excellent thermal stability

UV radiation stability

durable thermal cycling performance

as well as high transparency

good hydrophobicity. However

the refractive index difference between the silicone encapsulant and the chip material usually cause noticeable loss of the light output. How to enhance the silicone encapsulant' s refractive index in order to improve the light output efficiency of LED has become one of the hot points in this area. This review reports the research progress of the silicone based LED encapsulants with high refractive index in the near decade. There are mainly three ways to enhance the refractive index of the encapsulants according to the literature

that includes introducing hetero- atoms into the molecular chain

introducing phenyl groups attached to silicon and introducing inorganic nano-particles to the material. The progress in this field is also illustrated by analysis the changes of the amount of the publication and patent disclosed in the recent years.