Novel lighting properties of white LEDs with two-layered remote phosphor package using red-emitting α-SrO·3B2O3:Sm2+ phosphor

• Main Authors: Minh Tran Hoang Quang, Nhan Nguyen Huu Khanh, Anh Nguyen Doan Quoc, Lee Hsiao-Yi
• Format: Article
• Language: English
• Published: Sciendo 2017-10-01
• Series: Materials Science-Poland
• Subjects: remote phosphor structure; two-layered package; luminous flux; color rendering index; light emitting diodes (leds)
• Online Access: https://doi.org/10.1515/msp-2017-0071

This paper investigates a method for improving the lighting performance of white light-emitting diodes (WLEDs), packaged using two separating remote phosphor layers, yellow-emitting YAG:Ce phosphor layer and red-emitting α-SrO·3B2O3:Sm2+ phosphor layer. The thicknesses of these two layers are 800 μm and 200 μm, respectively. Both of them have been examined at average correlated color temperatures (CCT) of 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor has been varied from 2 % to 30 % in the upper layer, while in the lower layer the yellow phosphor concentration was kept at 15 %. It was found interesting that the lighting properties, such as color rendering index (CRI) and luminous flux, are enhanced significantly, while the color uniformity is maintained at a level relatively close to the level in one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer have been revised by combining Kubelka-Munk and Mie-Lorenz theories. Through the analysis, it is demonstrated that the packaging configuration of two-layered remote phosphor that contains red-emitting α-SrO·3B2O3:Sm2+ phosphor particles provides a practical solution to general WLEDs lighting.