Luminescence enhancement and color regulation of Sr2LiAlO4-1.5xNx: Eu2+ phosphor for high color rendering index white LED applications

Abstract

The color rendering index (CRI) of white light-emitting diodes (LEDs) is very important for lighting quality. Currently, high-CRI white LEDs are typically fabricated by combining multiple-color phosphors. Therefore, the realization of multipeak-emission phosphors in a single phosphor is valuable. The Sr₂LiAlO₄: Eu²⁺ phosphor exhibits an obvious double-peak emission in the yellow-green spectral range and has excellent luminescence properties, suggesting its potential application in white LEDs. In this study, a series of Sr₂LiAlO_4-1.5xN_x: Eu²⁺ (x = 0–0.7) phosphors were successfully synthesized by introducing N³⁻ ions to replace O²⁻ ions. The luminescence intensity was significantly enhanced by increasing the N³⁻ concentration. Upon reaching a concentration of 0.7, the intensity of the yellow emission exceeded that of the green emission, indicating a shift in emission color from green to yellow. The emission peak of the Sr₂LiAlO_2.95N_0.7: Eu²⁺ phosphor is at 568 nm, which exhibited broader yellow light emission. Finally, Sr₂LiAlO_2.95N_0.7: Eu²⁺ was fabricated with a CaAlSiN₃: Eu²⁺ red phosphor on 450 nm blue LED chips. The fabricated white LEDs was observed to be white light with a high CRI of 92.1 and an adjustable color temperature (4938-6665k), showing its potential application in white LEDs.