Enhancing the cyan light emission of Ba9Lu2Si6O24:Ce phosphors by crystal-site engineering for full spectrum lighting

Filling the cyan gap is the key element in achieving full-spectrum illumination using violet chip to excite red, green and blue phosphors. However, designing cyan phosphors suitable for violet light excitation with excellent performance remains challenging. Herein, a novel cyan phosphor Ba₉Lu_2-x-nSi₆O₂₄:xCe (n-BLS:Ce) with multiple crystal sites of Ba²⁺ and Lu³⁺ for Ce³⁺ ions was designed and prepared via crystal-site engineering. The Ce³⁺ ions at Ba²⁺ sites emit ultraviolet light at 385 nm under 325 nm ultraviolet light excitation, and the Ce³⁺ ions at Lu³⁺ sites emit cyan light at 485 nm under 395 nm violet light excitation. The favorable occupation of Ce³⁺ ions at Lu³⁺ sites could be realized by introducing Lu vacancies. Significantly, the cyan light emission intensity of Ba₉Lu_1.4Si₆O₂₄:0.3Ce (n_0.3-BLS:Ce) with Lu vacancies is effectively improved by 47 % compared to Ba₉Lu_1.7Si₆O₂₄:0.3Ce (n₀-BLS:Ce) without Lu vacancies. And the emission intensity at 150 °C retains 96 % of that at room temperature. The color rendering index increases from 87.9 to 94.5 after supplementing Ba₉Lu_2-x-nSi₆O₂₄:xCe cyan phosphor in w-LEDs devices combining commercial red, green, and blue phosphors with a violet chip, indicating its potential practical application in full-spectrum lighting. This work also provides new ideas for the design and development of new and efficient high-quality light-emitting materials.