High-Brightness Red-Emitting Phosphor La₃(Si,Al)₆(O,N)₁₁:Ce³⁺ for Next-Generation Solid-State Light Sources

A novel high-brightness red-emitting phosphor, La₃(Si,Al)₆(O,N)₁₁:Ce³⁺ (LSA), which can potentially be used as a laser-excited light source, is demonstrated. Laser-excited phosphor system has great potential for use as a white-light source, as it is orders of magnitude brighter than white LEDs. Although conventional yellow-green phosphors show excellent luminescent properties even under high-power laser excitation, red-emitting phosphors, which are essential to achieve a high color-rendering index and low color-temperature, show quantum efficiency quenching. This limits the output power in multiphosphor excitation systems. Ce³⁺ should successfully tolerate high-power excitation due to the shortest emission lifetime seen in rare-earth ions, caused by the 5d¹-4f¹ spin-allowed transition; however, a red-emitting Ce³⁺-doped phosphor of practical use has not been realized. LSA is described by the crystal-field modification of a yellow-emitting phosphor, La₃Si₆N₁₁:Ce³⁺, with substitution of Al in Si sites. LSA shows 640 nm red emission together with tolerance for high-power excitation and thermal quenching, suggesting its significant potential for industrial applications that require ultrahigh brightness.