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 Eu²⁺ -doped red-emitting oxide-based phosphors remains one of the significant challenges for white light-emitting diodes (WLEDs). Selective occupation of Eu²⁺ in inorganic polyhedra with small coordination numbers results in broad-band red emission as a result of enhanced crystal-field splitting of 5d levels. Rb₃ YSi₂ O₇ :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 Eu²⁺ ions preferably occupy RbO₆ and YO₆ polyhedra and show the characteristic red emission band of Eu²⁺ . 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.