Ce-Doped LaSiAlNO, a Rare Highly Efficient Blue-Emitting Phosphor at Short Wavelength toward High Color Rendering White LED Application.

Phase pure nondoped and Ce doped LaSiAlNO (Al containing La N-phase) samples have been obtained by solid-state reaction synthesis for the first time. 1% Ce-doped LaSiAlNO phosphor displays a broad excitation band ranging from UV to 410 nm, with a maximum at 355 nm. UV light excitation results in a narrow Ce 5d-4f emission band (fwhm = 68 nm) centered at 418 nm. The emission can be tuned from 417 nm at 0.5% Ce to 450 nm at 50% Ce. A high internal quantum efficiency up to 84% is achieved for a 1% Ce doped sample, which has CIE chromaticity coordinates of x = 0.157 and y = 0.069, close to the NTSC blue standard (x = 0.155; y = 0.070). Compared to LaSiON:Ce phosphor, the quantum efficiency and thermal stability have been enhanced for LaSiAlNO:Ce phosphor without shifting the emission peak wavelength. LaSiAlNO:Ce shows less thermal quenching than LaSiON:Ce and no shift or change in the shape of emission spectra with increasing the temperature from 4 to 573 K. These results show that LaSiAlNO:Ce is more efficient than any other (oxy-)nitride phosphor with an emission in the short wavelength blue region (400-450 nm). A white LED was fabricated using the LaSiAlNO:5%Ce as a blue phosphor. The high color rendering index (Ra = 93.2, R9 = 91.4, and R12 = 89.5) obtained shows that the phosphor is a very promising conversion phosphor for white LEDs.