In this paper, a new structure of spatial-coded coating phosphor is proposed and effectively benefits the efficiency enhancement in the white light-emitting diodes (LEDs). The spatial-coded phosphor plate contains two subregions. One subregion is of the yellow phosphor for providing the greatest extracted yellow light, and the other subregion is the open windows for preventing the blue light from the absorption by the yellow phosphor and the Stoke loss in the wavelength conversion. In the design process, the thickness and the concentration of the phosphor and photon recycling in a high-reflectivity cavity are all simulated and optimized. Finally, the predicting spectra of the resultant white LEDs with the spatial-coded phosphors by the simulation model are all in very good agreement with the corresponding spectra from the practical measurements. Moreover, as the correlated color temperature (CCT) is around 6500 K, the maximal packaging efficiency of the white LEDs with the spatial-coded phosphors is as high as 68.0% in the measurement, and the corresponding simulation is 71.8%. It is much higher even than the optimal packaging efficiency of the conventional conformal or remote-dome phosphor packaging structure.

We performed the simulation of white LEDs packaging with different chessboard structures of white light converting phosphor layer covered on GaN die chip. Three different types of chessboard structures are called type 1, type 2 and type 3, respectively. The result of investigation according to the phosphor thickness show the increasing of thickness of phosphor layer are, the decreasing of output blue light power are. Meanwhile, the changes of yellow light are neglect. Type 3 shows highest packaging efficiency of 74.3 % compares with packaging efficiency of type 2 and type 1 (72.5 % and 71.3 %, respectively). Type 3 also shows the most effect of forward light. Attention that the type 3 chessboard structure gets packaging efficiency of 74.3 % at color temperature of daylight as well as high saving of phosphor amount. The color temperatures of three types of chessboard structure are higher than 5000 K, so they are suitable for lighting purpose. The angular correlate color temperature deviation (ACCTD) of type 1, type 2 and type 3 are 6500K, 11500K and 17000K, respectively

Pyramidal nature PSS (n-PSS) substrates were produced by a simple wet etching process without standard lithography and dry-etching processes. We found that the output power of the LED on the pyramidal n-PSS substrates is larger than the output power of the LED chip on the flat c-plane sapphire substrate by 46.4% to 51.5%. LED chip on the n-PSS(III) substrate with 73% pattern coverage has the highest output power among LED chips on all n-PSS substrates. The light emission patterns of LED bare chips on different n-PSS and r-PSS substrates were studied. The shape of the light emission pattern was qualitatively defined by the broadness angle, which is the angle at the maximum intensity of the light emission pattern away from the normal direction. The broadness angle is inversely proportional to the facet angle of pyramids created on the n-PSS substrates. In addition, we found that the light extraction efficiency at the GaN/silicone interface has a dependence on the light emission pattern of the bare chips on different n-PSS substrates. The broader light emission pattern (larger broadness angle) would result in higher light extraction efficiency at the GaN/silicone interface. (C) 2015 Optical Society of America

In this paper, we start from the study on the packaging efficiency of the phosphor-converted white LED via a new way to measure and calculate the blue light from the blue die to the encapsulation lens. Then we try to estimate the limit of luminous efficacy of a pcW-LED with Type VII structure. In the calculation, with the EQE of 81% of the blue die and Stokes loss, we obtain the optimal limit of luminous efficacy. The largest one reaches 300 lm/W, and occurs for green-white light with CCT from 4000K to 5000K. More practical limit is calculated in considering phosphor quantum loss and geometry loss, and the practical limit of luminous for CRI around 60 is around 210 lm/W, and for CRI larger than 80 is around 175 lm/W. Luminous efficacy will be sacrificed to obtain higher CRI. In order to know the real optical flux on the illuminated target, we introduce the optical utilization factor (OUF). Three application cases are discussed. The OUFs for light bulb, automotive head lamp, and street light are 90%, 60% and 45%, respectively. In considering human factors, it is interesting to find that a light source with lower luminous efficacy can perform higher illumination luminous efficacy (ILE). Therefore it is important to use ILE rather than LE when a light source is practically applied to lighting.