Giant luminescence enhancement in Li2MSiO4:Eu2+ (M = Sr, Ba) via two-step synthesis and charge compensation

Eu 2+ -activated phosphors are prominent candidates for next-generation solid-state lighting, but their performance is often limited by incomplete Eu 3+ reduction and poor thermal stability. Herein, we present a universal strategy combining a two-step synthesis with charge compensation to simultaneously stabilize Eu 2+ centers and suppress parasitic Eu 3+ . Initially, M 2 SiO 4 :Eu 2+ ( Pnma ) precursors were synthesized to promote effective Eu 2+ incorporation. Subsequent P 5+ co-doping induces charge-compensated substitution (Si 4+ →P 5+ ). This structural evolution yields the target phosphor phases: the yellow-emitting Li 2 SrSi 0.96 P 0.04 O 4 :Eu 2+ ( P 3 1 21) and the green-emitting Li 2 BaSi 0.96 P 0.04 O 4 :Eu 2+ ( P 6 3 cm ) with excitation/emission maxima at 394/580 and 365/520 nm, respectively. Importantly, the heterovalent substitution facilitates the Eu 3+ →Eu 2+ reduction and optimizes the defect distribution. Consequently, the photoluminescence quantum yield (PLQY) is significantly enhanced from 26% to 78% for Li 2 SrSi 0.96 P 0.04 O 4 :Eu 2+ and from 32% to 83% for Li 2 BaSi 0.96 P 0.04 O 4 :Eu 2+ , along with improved thermal stability (93.3%@450 K). Fabricated near-UV pumped white light-emitting diodes (LEDs) incorporating these phosphors demonstrate superior color rendering ( Ra = 91.1) and stable electroluminescence across varying currents. The robust Eu 2+ stabilization and charge compensation paradigm paves the way for rational design of high-performance phosphors for advanced lighting.