Site‐Selective Occupancy of Eu²⁺Toward Blue‐Light‐Excited Red Emission in a Rb₃YSi₂O₇:Eu Phosphor

Establishing an effective design principle in solid‐state materials for a blue‐light‐excited Eu 2+ ‐doped red‐emitting oxide‐based phosphors remains one of the significant challenges for white light‐emitting diodes (WLEDs). Selective occupation of Eu 2+ in inorganic polyhedra with small coordination numbers results in broad‐band red emission as a result of enhanced crystal‐field splitting of 5d levels. Rb 3 YSi 2 O 7 :Eu exhibits a broad emission band at λ max =622 nm under 450 nm excitation, and structural analysis and DFT calculations support the concept that Eu 2+ ions preferably occupy RbO 6 and YO 6 polyhedra and show the characteristic red emission band of Eu 2+ . The excellent thermal quenching resistance, high color‐rendering index R a (93), and low CCT (4013 K) of the WLEDs clearly demonstrate that site engineering of rare‐earth phosphors is an effective strategy to target tailored optical performance.