Single‐Phase White‐Light Emission in Eu 2+ ‐Activated UCr 4 C 4 ‐Type Phosphors via Crystallographic Site Engineering

Single‐phase white‐emitting luminescent materials are ideal for high‐quality lighting applications. However, achieving white emission across the full spectral range in single‐dopant activated luminescent materials remains challenging. Herein, Eu 2+ ‐activated RbK 7 (Li 3 SiO 4 ) 8 :Eu 2+ (Rb 1 K 7 :Eu 2+ ) phosphor was developed based on crystallographic site engineering, which shows a narrow‐band blue emission at 460 nm, ascribed to the 5d→4f transition of Eu 2+ at Rb sites, and a broad‐band red emission at 630 nm, originating from the defect‐induced charge transfer. Compared with Rb 1 K 7 :Eu 2+ , Rb 1.5 K 6.5 (Li 3 SiO 4 ) 8 :Eu 2+ (Rb 1.5 K 6.5 :Eu 2+ ) exhibits a more continuous emission with increasing Rb + content, featuring an additional green emission at 540 nm, attributed to Eu 2+ at K1/K2 sites. The Rb 1.5 K 6.5 :Eu 2+ shows white emission with a high photoluminescence quantum yield (PLQY) under 390 nm near‐ultraviolet excitation. Given that the three emission peaks exhibit distinct response characteristics under different temperatures and excitation wavelengths, an optical thermometer and optical anti‐counterfeiting were designed. Finally, a single‐phase phosphor‐converted white light‐emitting diode (pc‐WLED) fabricated by employing the Rb 1.5 K 6.5 :Eu 2+ demonstrates well‐distributed white light with a high color‐rendering index (CRI) of 92.5 and a low correlated color temperature (CCT) of 5477 K. These results provide a new design strategy for single‐phase white‐emitting materials utilizing crystallographic site engineering.