Design of K2SrCa(PO4)2-x(BO3)x:Eu2+ phosphors with full-visible spectrum by crystal structure modification

In recent years, much attention has been paid to the development of rare-earth-activated borophosphate phosphors for white light-emitting diodes (LEDs). Herein, Eu 2+ single-doped K 2 SrCa(PO 4 ) 2-x (BO 3 ) x white phosphors with full-visible-spectrum continuous emission in the range of 400 nm–720 nm were developed by the modification of the local structure in the crystal. The structural variation resulted from the substitution of (PO 4 ) 3- ions by (BO 3 ) 3- in host lattice were investigated in detail by X-ray powder diffraction and Fourier transform infrared spectroscopy. Furthermore, the phase structure of sample was also confirmed by the Rietveld method, indicating its Rhombohedral structure with the R-3c space group and the occupation of K and Ca sites by Eu 2+ ions, then combined luminescence lifetime decay, revealing insights of site-selective occupation of Eu 2+ in the borophosphate white light phosphors. The emission spectra of K 2 SrCa(PO 4 ) 1.4 (BO 3 ) 0.6 :0.05Eu 2+ phosphor exhibited full-visible-spectrum continuous emission centered at 455 and 595 nm by adjusting the concentration of the (BO 3 ) 3- groups under near ultraviolet excitation at 365 nm. Especially, the WLEDs obtained from the broad-spectrum phosphors showed ultra-high color quality of color rendering index (CRI) values (R a = 95, R 9 = 66, and R 13 = 95) and excellent fidelity/gamut index values (R f = 94 and R g = 98), which was almost similar to sunlight streaming. The investigation results indicated that the device by using as-prepared K 2 SrCa(PO 4 ) 1.4 (BO 3 ) 0.6 :0.05Eu 2+ phosphor could be a potential candidate for full-spectrum lighting. • Devising KSrCaPB:Eu 2+ phosphors with full-visible-spectrum emission by the modification of local crystal structure. • Revealing insights of site-selective occupation of Eu 2+ in the borophosphate white light phosphors. • WLEDs device obtained from the broad-spectrum phosphors shows ultra-high color rendering index values (Ra=95).