Crystal structure, Bi3+ yellow luminescence, and high quantum efficiency of Ba3SbAl3Ge2O14:Bi3+ phosphor for white light-emitting diodes

Abstract

Bi³⁺-activated luminescent materials have attracted increasing attention owing to their strong excitation in the near-ultraviolet (NUV) range instead of the visible range. Such a unique feature allows them to avoid reabsorption among phosphors, resulting in their growing popularity in research and applications. However, the majority of Bi³⁺-doped phosphors suffer from low quantum efficiency, imposing limitations on their practical applications. We hereby present a newly developed phosphor, Ba₃SbAl₃Ge₂O₁₄:Bi³⁺ (BSAG:Bi³⁺), which emits a vibrant yellow light when excited by NUV light. Importantly, this phosphor exhibits a high internal quantum efficiency (IQE) of 95.3%, marking a significant advancement in the field. Through charge compensation, BSAG:Bi³⁺, K⁺ phosphor achieves a remarkable IQE of 97.2%. The photoluminescence (PL) spectroscopy analysis reveals that this phosphor contains only one Bi³⁺ luminescent center, which is consistent with the trigonal structure of BSAG. This is supported by the fact that only one Ba site in the structure can accept Bi³⁺ ions. The critical distance was estimated to be 9.71 Å. The energy transfer mechanism between Bi³⁺ ions was determined as a dipole–dipole interaction. To explore the application of BSAG:Bi³⁺ phosphor, pc-WLED devices were fabricated by depositing a blend of this phosphor and one or two commercial phosphors on a 365 nm chip. The final warm pc-WLED device exhibits ideal photoelectric performance with a low CCT of 4229 K and a high Ra of 91.5.