Angular color uniformity improvement for phosphor-converted white light-emitting diodes by optimizing remote coating phosphor geometry

Abstract

Angular color uniformity (ACU) of a king of popular remote phosphor coating LED packaging with spherical phosphor shape with uniform thickness was invested by the Monte Carlo ray tracing method. The simulation results indicate the yellowish ring can't be avoided under uniform phosphor thickness in angular range of 0°-180°. The optimized phosphor geometry was proposed whose thickness gradually reduces from the center to the edge. The optimized phosphor geometry can improve ACU 45%, compared with the initial uniform thickness phosphor layer.

Dip-transfer phosphor coating on designed substrate structure for high angular color uniformity of white light emitting diodes with conventional chips

“…The specular and diffused reflection coefficients of top surfaces of substrates are assumed to be 78% and 9%, respectively. Optical properties of the phosphor layer are calculated by the Mie theory [10]. The phosphor concentration was chosen as 1.2 g/cm 3 .…”

“…However, in this coating method, yellow ring phenomenon usually occurs in the radiation pattern and results in bad ACU. Compared with the dispensing coating, the conformal phosphor coating shows strong attraction due to its high ACU performance in theory [8][9][10][11][12][13]. This method demands that a phosphor layer with uniform thickness replicates the LED chip shape.…”

An Emerging White LED Technology and associated Thermal Issues – A Review

“…The phosphor response profoundly relies upon the temperature of LED chip, and, while temperature increases, its emission efficiency decreases. This issue can be solved by remote configuration where a separation exists between the chip and phosphor layer [72,73]. But, despite of the distance, an increase in temperature in phosphor layer affects the life of remote phosphor LED [74].…”