A new coating configuration with two phosphor layers laminated for white PC-LEDs

A ray tracing program which simulates white light emission of the pc-LEDs has been developed in this Lab. A comprehensive survey on the parameters (thickness, shape and concentration of phosphor coating) that effect color conversion and light scattering within phosphor layer of white pc-LEDs was performed. The impact of geometry of phosphor conversion layer on the angular correlated color temperature distribution was discussed intensively in this paper. Our simulation reveals that diffused blue light from LED chip was largely forward-scattering into the range of 0-20 degrees while the yellow converted light was emitted isotropically, which causes the bluish center and yellowish fringe for the conventional coating structure such as convex, concave and conformal configuration. A new coating configuration with two phosphor layers laminated is proposed in this paper to achieve a better consistency of blue to yellow ratio at different angles. With statistical analysis of the simulation results, the new laminated phosphor distribution reduces the CCT deviation by 44% in comparison with conventional convex and conformal coating. Moreover, the optimized designs of coating geometry not only implement smaller CCT deviation but also are suitable for mass production.