Analysis of high-power packages for phosphor-based white-light-emitting diodes

An optimized packaging configuration for high-power white-light-emitting diode (LED) lamps that employs a diffuse reflector cup, a large separation between the primary emitter (the LED chip) and the wavelength converter (the phosphor) and a hemispherically shaped encapsulation is presented. Ray tracing simulations for this configuration show that the phosphor efficiency can be enhanced by up to 50% over conventional packages. Dichromatic LED lamps with phosphor layers on the top of a diffuse reflector cup were fabricated and studied experimentally. The experimental enhancement of phosphor efficiency is 15.4% for blue-pumped yellow phosphor and 27% for ultraviolet-pumped blue phosphor. Those improvements are attributed to reduced absorption of the phosphorescence by the LED chip and the reduction of deterministic optical modes trapped inside the encapsulant.