Cation‐Engineered Narrow‐Band Green Emitting Phosphor Toward High‐Performance Laser‐Driven Displays

ABSTRACT

Wide color gamut and high brightness are critical performance metrics for advanced displays like projectors. Combining narrow‐band green and red color converters with a blue laser‐driven light source is one of the most effective solutions to achieve these goals. In this work, an efficient UCr ₄ C ₄ ‐type narrow‐band green‐emitting phosphor Cs ₂ NaK(Li ₃ SiO ₄ ) ₄ :Eu ²⁺ was obtained by partially substituting Na ⁺ with Cs ⁺ in cyan‐emitting CsNa ₂ K(Li ₃ SiO ₄ ) ₄ :Eu ²⁺ . This cation‐substitution strategy preferentially directs Eu ²⁺ ions to occupy the Na sites over the K sites, resulting in a transition from dual peaks at 485 and 527 nm to a single peak at 527 nm. The site occupation evolution mechanism of Eu ²⁺ was investigated using Rietveld structural refinement, low‐temperature transient and steady‐state photoluminescence spectroscopy, and density functional theory (DFT) calculations. Under 450 nm excitation, Cs ₂ NaK(Li ₃ SiO ₄ ) ₄ :Eu ²⁺ phosphor demonstrates a high external quantum efficiency (EQE) of 38.1% and good thermal stability (emission intensity retains 84.5% @ 145°C). When fabricated into a color wheel and excited by a 450 nm blue laser with a power density of 27.1 W/mm ² , the phosphor achieves a luminous flux of 1677.6 lm and a luminous efficacy of 98.7 lm/W, demonstrating its potential for laser‐driven projection displays.