Accurately Controlling the Occupation of Eu²⁺ in Cs(K, Na)₃(Li₃SiO₄)₄ to Achieve Narrow-Band Green Emission for Wide Color Gamut Displays

The development of narrow-band phosphors for wide color gamut displays in multimodal phosphors through selective site occupancy engineering is an important challenge. In this work, by replacing Na ions with K ions in the cyan-green double-band emitting phosphor CsK0.9Na2(Li3SiO4)4: 10%Eu2+, the occupation of Eu2+ in Cs(K, Na)3(Li3SiO4)4 was accurately controlled from occupying three sites of Cs, K1, and Na to occupying only one site of K2/Na. The obtained phosphor CsK1.9Na(Li3SiO4)4: 10%Eu2+ exhibits a single narrow-band green emission at 531 nm (the full width at half-maximum of 46 nm) with excellent thermal stability of luminescence from 80 to 523 K (96.3% @423 K of the intensity of integrated emission at room temperature and 94.9% @300 K of the intensity of integrated emission at 80 K). The white light-emitting diode (wLED) that was fabricated by combining a blue LED chip with this narrow-band green phosphor and red phosphor K2SiF6: Mn4+ presents a satisfactory wide color gamut of 128.1% of the National Television Standards Committee, which demonstrates the important application value of the phosphor in the wide color gamut displays field. This work provides an effective design strategy for exploring narrow-band phosphors through selective site occupancy engineering, which will facilitate the exploration of relevant narrow-band emitters in the future.