g-Chien Chen

High uniformity in angular correlated-color-temperature distribution of white LEDs from 2800K to 6500K.

In this paper, to our best knowledge, it is the first time to present a precise simulation and detailed design of angular correlated color temperature (CCT) distribution of white LEDs covering a range of CCT from 2800K to 6500K. An optimized design of packaging structure with a silicone lens covering a phosphor dome performed an extreme small angular CCT deviation of 105K in the simulation and 182K in a corresponding real sample for a white LED with the CCT near 6500K.

Precise optical modeling for silicate-based white LEDs

In this paper, as to our best knowledge, we propose and demonstrate the first precise phosphor modeling scheme to simulate the chromatic performance of white LEDs with silicate phosphors. The phosphor model is useful to accurately simulate the power ratio of the blue and yellow lights emitted by the white LEDs and is important in white LED package.

Essential Factor for Determining Optical Output of Phosphor-Converted LEDs

An essential factor of the particle number is exploited for the phosphor excitation in phosphor-converted white LEDs. The particle number can clearly reveal the dependence of the light output flux and the correlated color temperature upon the conventional parameters, thickness, and concentration of the phosphors in a simpler way. In addition, we also find that there might exist an optimal particle number for the maximal luminous light output. An empirical function is then proposed for successfully modeling the relation between the output light and the particle number.

Planar light source by using side-emitting of GaN die with top and bottom reflector

Based on Monte Carlo ray tracing we present a study of GaN die with a reflective layer coated on a p-GaN surface inside the light guide as a planar light source. We simulated the lights extracted from the GaN die implanting pyramid microstructure on the top surface of sapphire or on the top surface of p-GaN. Micro pyramid array with different slanted angle from 50 to 850 is shown to effectively improve the light extraction efficiency. In addition, the pattern sapphire substrate with slanted angle of ten degrees is found to be an effective way to increase the lateral directionality than the surface texture.

Optical performance as a function of phosphor particle number in white LED

In this paper, we demonstrate a method to calculate the phosphor particle numbers and study the relationship among phosphor particle numbers, light output and correlated color temperature (CCT) of LEDs under remote package type and dispensing package type. We also discuss the influence of the thickness and concentration of phosphors on the performance of LEDs. We compare the various thicknesses and concentrations to check the resultant CCT and the output flux, where we can see that the lumen output is almost equal as the phosphor particle numbers is similar with the CCT at 6500±200 and 5000±100 K under the remote package type.

Packaging efficiency analysis of phosphor-converted white LEDs

In this paper, we present our study in packaging efficiency for phosphor-converted white LED (pcW-LED). Then the limit of luminous efficacy of a pcW-LED in different types of packaging is estimated. In the calculation, the EQE of the blue die is assumed 81% and the Stokes loss is counted, we obtain the limit of luminous efficacy, which reaches 300 lm/W, when the color appearance is green-white and the corresponding CCT is between 4000K to 5000K. More consideration for practical limit take consideration of phosphor quantum loss and geometry loss, and the limit of luminous for CRI around 60 is around 240 lm/W, and for CRI larger than 80 is around 175 lm/W.