Triple-layer remote phosphor structure: A potential packaging configuration to enhance both color quality and lumen efficiency of 6,000–8,500 K WLEDs

Le, Phan Xuan; Ho, Sang Dang; Quoc Anh, Nguyen Doan; Lee, Hsiao-Yi

doi:10.2478/msp-2021-0037

Abstract

To achieve further enhancement in the lighting quality of white light-emitting diodes (WLEDs), this study proposed a packaging structure with three different phosphor layers, called triple-layer remote phosphor structure. This structure can provide an overall control over the light color distribution of WLEDs. The yellow-green-emitting CaAl₂O₄:Mn²⁺ phosphor and red-emitting CaMoO₄:Eu³⁺ phosphor are used along with the original yellow-emitting YAG:Ce³⁺ phosphor to fabricate the triple-layer structure. The concentration of yellow-emitting YAG:Ce³⁺ phosphor is required to be decreased as the concentrations of other phosphors increase to keep the predetermined correlated color temperatures. The color rendering index (CRI) and the color quality scale (CQS) are measured to reach a thorough color quality assessment for WLEDs. The color management can be achieved by adjusting the concentration of red-emitting CaMoO₄:Eu³⁺ phosphor to enhance the red emission. In addition, adjustment of the concentration of yellow-green-emitting CaAl₂O₄:Mn²⁺ phosphor can result in higher luminous efficiency owing to its control over the green light components. Higher CRI is observed when CaMoO₄:Eu³⁺ concentration increases, while an increase in CaAl₂O₄:Mn²⁺ phosphor leads to much lower CRI. The CQS – on the other hand – is remarkably high when the CaMoO₄:Eu³⁺ concentration range is about 10wt%–14wt%, regardless of the proportion of the CaAl₂O₄:Mn²⁺ phosphor. Furthermore, 40% enhancement in luminous efficiency is also achieved since light scattering is minimized by the boosted green-light emission spectra. Manufacturers can take these findings as reference to fabricate high-quality WLED lights that fulfill all their requirements.

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Triple-layer remote phosphor structure: A potential packaging configuration to enhance both color quality and lumen efficiency of 6,000–8,500 K WLEDs

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