Building superior lighting properties for WLEDs utilizing two-layered remote phosphor configurations

Abstract

The remote phosphor structure produces higher luminous flux but delivers poorer color quality than the conformal or in-cup phosphor structure. To eliminate this weakness, researchers have attempted to improve the chromatic properties of remote phosphor package. This study tends to enhance lighting features for WLEDs including color quality and luminous flux in general or color rendering index (CRI) and color quality scale (CQS) in particular by applying dual-layer remote phosphor structure. In the simulation section, we utilize two identical LEDs that only differ in correlated color temperature values which are 6600 K and 7700 K. The study offers an idea of placing a yellow-green phosphor layer SrBaSiO4:Eu2+ or a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then modifying the concentrations of SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ to the suitable values to improve the color quality and lumen output of WLEDs. The results show that red phosphor layer SrwFxByOz:Eu2+,Sm2+ has a significant influence on CRI and CQS improvement. Particularly, the increase of SrwFxByOz:Eu2+,Sm2+ concentration leads to increased CRI and CQS because the red light component increases in WLEDs. On the other hand, the green phosphor layer SrBaSiO4:Eu2+ only brings benefit to the luminous flux. However, the WLEDs’ luminous flux and color quality drop sharply, when SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ concentrations rise extremely, which is verified based on the Mie-scattering theory and the Lambert-Beer law. In short, the article provides general knowledge and primary information for the production of higher-quality WLEDs.

Selection of Multi-layer Remote Phosphor Structure for Heightened Chromaticity as well as Lumen Performance within WLED Devices

“…Additionally, these methods directly placed the phosphor layer onto the LED chip surface, stimulating calefaction at the joint and reducing the phosphor's efficiency and the lifetime of the LED device. Hence, researchers devised the idea of creating a gap or adding another film between the main phosphor-silicone encapsulation and the LED chip to improve light extraction and minimize heat generation (Anh et al, 2020;Zhang et al, 2016). This structure was called the remote phosphor structure, and it fastly became a popular topic in various studies of enhancements for WLEDs' optical properties.…”

Studying CdS:In green phosphor's impacts on white-light emitting diode with higher luminous flux

“…Thus, when it comes to the advancing development of white LEDs, especially the mixed-type models, the color rendering index (CRI) or R a [1] and the lumen efficiency (LE) [2] are highly concentrated. The earlier studies [3][4][5] examined WLED devices' enhancement by achieving the highest radiation lumen efficiency (LER) or limited lumen efficiency (LLE) under several limited conditions, including pre-determined correlated color temperature (CCT) and R a . Besides, when utilizing the LLE, it is necessary to take into account the Stokes shift's wasted energy [6].…”

Comparison between SEPs of CaCO3 and TiO2 in phosphor layer for better color uniformity and stable luminous flux of WLEDs with 7,000 K

“…Yet, deficiencies in the color quality and the light extraction efficiency have been the obstacles preventing the phosphor-based LEDs from attaining a wider application in the SSL market [5]. In general, the phosphor-converted LED, using a YAG:Ce phosphor layer to coat the blue LED chip, generates white light by mixing the blue light from the chip that transmits through the phosphor layer with the converted yellow light produced by phosphors [6].…”