Laminated structure of phosphor-in-glass films on sapphire with high color rendering index and heat-conducting properties for high-power white LEDs/LDs

As an all-inorganic solid state lighting material, phosphor-in-glass (PiG) receives much attention in high-power white lighting. However, poor heat-dissipation performance and low color rendering index (Ra) caused by low doping concentration of phosphor limit its application in white laser diodes (wLDs). Herein, phosphor-in-glass films on sapphire (PiFS) with heat-conducting properties and high Ra were newly synthesized via screen printing technology, which is highly desired for high-power wLEDs/wLDs. The interfacial corrosion product of CaWO 4 between nitride phosphor (CaAlSiN 3 :Eu 2+ ) and borosilicate glass (BS-glass) was found and investigated in detail firstly to determine the sintering temperature . Laminated structure of PiFS with red layer inside and green layer outside was intentionally designed to effectively avoid “reabsorption” effect between the red and green emitting phosphors. Compared with the opposite laminated structure, the PiFS exhibited the higher luminance efficiency (LE) and better optical properties (Ra = 85, CCT = 5362, CIE = (0.3348, 0.3156)) in wLDs. Notably, the adjustable optical characteristics can be achieved by changing the concentration of phosphor, the number of printing layers and the driving current for the application of PiFS in wLED and wLDs. High quality white light in wLED with CIE coordinates (0.3679, 0.3648) was also acquired and showed the excellent color rendering property (Ra = 90.8) and low color correlated temperature (CCT = 4280 K). Further, the working temperature of PiFS stabilized at 47 °C when applied in wLDs (1 W), which greatly prevented the phenomenon of “thermal quenching” for the phosphors caused by high temperature under high power LDs. Thus, high Ra PiFS prepared by this strategy has better heat dissipation and optical properties than PiG, indicating a prospective application in high-power white LEDs/LDs.