Perovskite A-site symmetry tuning to achieve high quantum efficiency phosphor for WLED applications

In addition to being a typical red light emitting center, Eu3+ can also be used to study the evolution of lattice symmetry due to its unique electric dipole leap (5D0-7F2) sensitivity to the lattice environment. Here, we synthesized a series of Ba1-xSrxLa0.9LiWO6: 0.10Eu3+ (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 Sr2+ does not affect the lattice type avoiding the effect of phase transition on the luminescence intensity. The lattice symmetry reaches a minimum at Sr2+ concentration of 0.8, which corresponds exactly to the peak of the luminescence intensity. It demonstrated the feasibility of adjusting the occupancy symmetry of Eu3+ 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 O2− in the luminescence center neighbors. At the optimal doping concentration, Ba0.2Sr0.8La0.6LiWO6: 0.40Eu3+ 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.