An efficient perovskite-type Rb2CaPO4F:Eu2+ phosphor with high brightness towards closing the cyan gap

Along with the development of versatile trichromatic phosphors, the phosphors bridging the cyan gap between blue and green light have been an ongoing focus in simulating the full-visible-spectrum luminescence to satisfy the daily illuminating demands. Herein, an intriguing cyan-emitting phosphor Rb 2 CaPO 4 F:Eu 2+ belonging to the perovskite-type structural prototype was first time synthesized via the solid-state reaction. Structural analysis indicated that the typical Rb 2 Ca 0.90 PO 4 F:0.10Eu 2+ phosphor crystallizes in the orthorhombic structure with the space group of Pnma (62), and its cell parameters are equal to a = 12.913(5) Å, b = 5.989(4) Å, c = 7.440(1) Å, and V = 575.44(8) Å 3 . The fluorine-centered [FRb 4 Ca 2 ] octahedra interconnect with each other by sharing faces to build the one-dimensional perovskite-structure corrugated chains, which further connect with the [PO 4 ] tetrahedra to establish the structural framework of Rb 2 CaPO 4 F host. The electronic structure of Rb 2 CaPO 4 F matrix was studied by the first-principle calculation on the basis of the density functional theory, revealing an appropriate direct band of 4.76 eV. Pumped with the near-ultraviolet light, Rb 2 CaPO 4 F:Eu 2+ phosphor displayed a bright cyan emission covering from 400 to 600 nm with a broad FWHM of 142 nm. According to the Dexter theory, the concentration quenching mechanism of Eu 2+ -activated Rb 2 CaPO 4 F phosphor was classified as the dipole-dipole interaction. The Rb 2 CaPO 4 F:Eu 2+ phosphor not only exhibits a good thermal stability (I 443 K /I 298 K = 70%), but possesses a satisfactory internal quantum efficiency of 68% which is superior to most of the previously reported cyan-emitting phosphors. Consequently, it turns out that our perovskite-type Rb 2 CaPO 4 F:Eu 2+ phosphor can be considered as a promising candidate to fill the cyan gap toward the full-visible-spectrum light. The present work also demonstrates a great possibility for exploring the novel phosphors inspired by the mineral-type structural prototypes.