Highly bright broadband cyan-emitting CaLu2HfGaAl3O12:Ce3+ garnet phosphors for high-color-quality white light-emitting diodes
In this work, novel highly efficient cyan-emitting Ce 3+ -activated CaLu 2 HfGaAl 3 O 12 (abbreviated as CLHGAO) garnet-structured phosphors were synthesized using the high-temperature solid-state reaction route. Rietveld refinement results demonstrate the as-prepared samples belong to cubic space group Ia 3 ‾ d . These CLHGAO: x Ce 3+ ( x = 0.5–8%) phosphors possessed a broad absorption band in the 320–450 nm wavelength range with a maximum at 408 nm. Upon 408 nm excitation, the CLHGAO:0.5%Ce 3+ sample showed a broad cyan emission band within 425–750 nm wavelength range (emission peak: 493 nm; bandwidth: 95 nm), along with CIE color coordinates of (0.1939, 0.3533) and a high internal quantum efficiency of 81.9%. It is observed that, with increasing Ce 3+ doping concentration from 0.5% to 8%, the emission peak position of CLHGAO: x Ce 3+ moves from 493 nm to 527 nm, and the corresponding emission color changes from cyan to green. Besides, the thermal stability and color stability of CLHGAO:0.5%Ce 3+ phosphor at high temperature are also studied. A white LED device was fabricated by utilizing a 395 nm LED chip with as-prepared CLHGAO:0.5%Ce 3+ cyan-emitting phosphor and commercial (Ba,Sr) 2 SiO 4 :Eu 2+ green-emitting phosphor and commercial CaAlSiN 3 :Eu 2+ red-emitting phosphor, and it demonstrates a high-color-quality white light with high color rendering index of 91, low color correlated temperature of 3547 K and good luminous efficacy of 58.71 lmW −1 .
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