Exellent Color Quality and Luminous Flux of WLEDs Using Triple-Layer Remote Phosphor Configuration

Abstract

This study proposed a triple-layer remote phosphor (TRP) structure to improve the color and luminous flux of white LEDs (WLEDs). TRP structure consists of 3 different phosphor layers: yellow YAG:Ce³⁺ layer below, red CaMgSi₂O₆:Eu²⁺,Mn²⁺ phosphor on top and green layer Ba₂Li₂Si₂O₇:Sn²⁺,Mn²⁺  phosphor in the middle. Using red CaMgSi₂O₆:Eu²⁺,Mn²⁺ to control the red light component leads to increased color rendering index (CRI). Utilize the green CaMgSi₂O₆:Eu²⁺,Mn²⁺ phosphor to control the green light component results in the increase in luminous efficacy (LE) of WLEDs. Furthermore, when the concentration of these two phosphors increased, yellow layer concentration YAG:Ce³⁺ decreased to maintain average correlated color temperatures (ACCTs) in the range from 6000 K-8500K. Besides CRI and LE, color quality scale (CQS) is also analyzed through concentration control of green phosphor and red phosphor. The research results show that the higher the concentration of CaMgSi₂O₆:Eu²⁺,Mn²⁺, the better for CRI. In contrast, CRI decreased significantly when increasing the concentration of Ba₂Li₂Si₂O₇:Sn²⁺,Mn²⁺. Meanwhile, CQS achieve notable enhancement in the concentration range of 10% -14% CaMgSi₂O₆:Eu²⁺,Mn²⁺, regardless of Ba₂Li₂Si₂O₇:Sn²⁺,Mn²⁺ concentration. LE, in particular, can also increase by more than 40% along with the improvement of CRI and CQS with the reduction of the backscattered light and addition of green light. Research results are a valuable reference for producers who wish to improve the color quality and enhance the luminous flux of WLEDs.

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