Enhanced forward emission of YAG:Ce³⁺ phosphor with polystyrene nanosphere coating

A common configuration for solid-state lighting is a blue LED combined with a phosphor platelet that emits in the yellow and green. Inherently, the light from the phosphor is emitted isotropically, but in most applications it is desirable to tailor the angular emission so that more light is emitted forward. In this work we demonstrate an effective forward emission enhancement for a YAG:Ce(3+) phosphor platelet by coating the surface with several layers of 600 nm diameter polystyrene nanospheres. After the application of the optimal concentration of three layers of nanospheres, the normal direction emission of YAG:Ce(3+) increased about 27% by focusing the emission from high angles into the forward direction through the mechanism of Mie scattering. This angular emission tailoring technique did not reduce the total emitted power. This is a convenient way to tailor the emission angles for applications like projector display and automotive forward lighting.