Tunable emission and energy-transfer mechanism of single-phase Na3Y(PO4)2:Ce3+, Mn2+phosphors for white LEDs

Abstract

A series of color-tunable single-phase Na3Y(PO4)2:Ce3+, Mn2+ (NYPO:Ce,Mn) phosphors were synthesized by means of solid-state reaction method for white light-emitting diodes. First, the concentration of Ce (x = 0.07) in the NYPO phosphors was optimized according to the photoluminescence (PL) properties, and then the optimized NYPO:0.07Ce phosphor was selected to study the single-phase phosphor with various concentrations of the Mn (y = 0.01, 0.03, 0.05, 0.07) co-dopant. The physicochemical characterization of both the doped and co-doped samples was performed via X-ray powder diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. Further, for the investigation of the PL properties, emission spectra of both doped and codoped samples were recorded upon 375 nm excitation, and spectra of NYPO:Ce exhibited two distinct peaks around 424 nm (blue emission) and 527 nm (green emission) due to the 5d1 to 4f transitions of Ce3+ ions, while the co-doped NYPO:Ce, Mn phosphors exhibited three peaks, two of them are at 414 and 515 nm (blue and green emission, respectively) due to the 5d1–2f7/2,5/2 transitions of Ce3+ ions and third peak is closer to the red range (620 nm) due to the 4T1(4G)- 6A1(6S) transitions of Mn2+ in the visible spectrum. NYPO:0.07Ce, 0.05Mn emits the combination of the three emission peaks (blue, green, and red) resulted in bright white light with CIE chromaticity coordinates of (0.322, 0.317), CCT (6036 K), and CRI (93), at a suitable excitation wavelength of 375 nm. The emission due to the addition of rare-earth Ce3+ ions and metal activator Mn2+ ions to the NYPO proves that it may be potential phosphor for obtaining white-light emission and tunable luminescence.