Perovskite A-site symmetry tuning to achieve high quantum efficiency phosphor for WLED applications. Issue 3 (1st February 2023) - Zhao, Xinlong
Abstract: In addition to being a typical red light emitting center, Eu 3+ can also be used to study the evolution of lattice symmetry due to its unique electric dipole leap ( 5 D0 - 7 F2 ) sensitivity to the lattice environment. Here, we synthesized a series of Ba1-x Srx La0.9 LiWO6 : 0.10Eu 3+ (x = 0.0–1.0) phosphors and used the leap properties to establish a link between the evolution of the lattice environment and the luminescence properties. The introduction of Sr 2+ does not affect the lattice type avoiding the effect of phase transition on the luminescence intensity. The lattice symmetry reaches a minimum at Sr 2+ concentration of 0.8, which corresponds exactly to the peak of the luminescence intensity. It demonstrated the feasibility of adjusting the occupancy symmetry of Eu 3+ to achieve luminescence enhancement. The covalent effect on the luminescence properties in this system is weak compared to the environmental changes by analyzing the attraction of the cations to O 2− in the luminescence center neighbors. At the optimal doping concentration, Ba0.2 Sr0.8 La0.6 LiWO6 : 0.40Eu 3+ phosphor has excellent internal quantum efficiency 95.3%, good color purity 94.79%, and extremely standard color coordinates (0.667, 0.332). In addition, it still has 80.6% emission intensity at 200°C compared to room temperature, which means it has good thermal stability. The good comprehensive performance has laid an important foundation for its application in WLED.