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

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 Sr_wF_xB_yO_z:Eu²⁺,Sm²⁺ on the yellow phosphor layer YAG:Ce³⁺ and then modifying the concentrations of Sr_wF_xB_yO_z: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 Sr_wF_xB_yO_z:Eu²⁺,Sm²⁺ has a significant influence on CRI and CQS improvement. Particularly, the increase of Sr_wF_xB_yO_z: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 Sr_wF_xB_yO_z: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.