Exclusive confinement of Bi3+-activators in the triangular prism enabling efficient and thermally stable green emission in the tridymite-type phosphor CaBaGa4O8:Bi3+Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3dt01928d

Abstract

Recently, Bi³⁺-activated phosphors have been extensively studied for potential applications in phosphor-converted white light-emitting diodes (pc-WLEDs). However, Bi³⁺ activators usually exhibit low quantum efficiency and poor thermal stability due to the outermost 6s6p-orbitals of Bi³⁺ being strongly coupled with the host lattice, inhibiting potential applications. Herein, we rationally design a novel phosphor CaBaGa₄O₈:Bi³⁺, which adopts a tridymite-type structure and crystallizes in the space group of Imm2. CaBaGa₄O₈:Bi³⁺ presents a bright green light emission peaking at 530 nm with a FWHM narrower than 90 nm. Comprehensive structural and spectroscopic analyses unravelled that Bi³⁺ emitters were site-selectively incorporated into the triangular prism (Ca²⁺-site) in CaBaGa₄O₈:Bi³⁺ since there exist two distinct crystallographic sites that can accommodate the Bi³⁺ ions. An excellent luminescence thermal stability of 73% of the ambient temperature photoluminescence intensity can be maintained at 423 K for CaBaGa₄O₈:0.007Bi³⁺. Impressively, the quantum efficiency (QE) of CaBaGa₄O₈:0.007Bi³⁺ was remarkably improved to 47.2% for CaBaGa₄O₈:0.007Bi³⁺,0.03Zn²⁺via incorporating the Zn²⁺ compensators without sacrificing the luminescence thermal stability. The high thermal stability and QE of CaBaGa₄O₈:0.007Bi³⁺,0.03Zn²⁺ are superior to most of the Bi³⁺-activated green-emitting oxide phosphors. The perspective applications in pc-WLEDs for CaBaGa₄O₈:0.007Bi³⁺,0.03Zn²⁺ were also studied by fabricating LED devices.