Realization and optimization of bismuth-activated Ba3Ga2O5Cl2 yellow phosphor for high-quality white LEDs.

• Bright yellow-emitting Bi3+-activated phosphor was successfully synthesized. • Significant improvement in thermal stability via structural rigidity alteration. • Double the luminous intensity of phosphor by cation substitution. (Sr2+→Ba2+). • Dramatic increase in quantum yield from 34.7 % to 85 % via introducing Sr2+. The development of high-quality lighting requires phosphors with excellent performance, and dramatically optimizing the luminescent properties of phosphors is a major challenge. Herein, a novel bismuth-activated yellow phosphor (Ba 3 Ga 2 O 5 Cl 2 :Bi3+) was firstly prepared by a multi-step solid-state reaction, and the crystal structure, luminescence characteristics, decay time, and thermal stability of the phosphor were systematically studied. Subsequently, the cation substitution strategy (Sr → Ba) was adopted to improve the optical properties. A comparison of the thermal quench performance of the phosphors before and after Sr substitution reveals that this strategy can effectively improve the thermal stability from 17.3 %@423 K to 61.1 %@ 423 K. More importantly, the luminescence intensity of the optimized phosphor was increased by about two times, and the quantum yield was significantly improved from 34.7 % to 85.0 %. Such a large improvement could be rationalized by the modulation of the local structure of Bi3+ ions or the change of band gap when Sr and Ba coexist in the host lattice. In addition, a WLED was prepared by combining Ba 2.55 Sr 0.45 Ga 2 O 5 Cl 2 :Bi3+ with commercially available blue phosphor (BaMgAl 10 O 17 :Eu2+) and red phosphor (CaAlSiN 3 :Eu2+) on a 365 nm LED chip, which achieved full-spectrum illumination and demonstrated potential applications. [ABSTRACT FROM AUTHOR]