Filling the cyan gap toward full-visible-spectrum LED lighting with Ca2LaHf2Al3O12:Ce3+ broadband green phosphor

Abstract

In this paper, a new garnet-based Ce3+-activated Ca2LaHf2Al3O12 (CLHAO) green phosphor with broadband emissions covering the cyan and green regions was successfully designed. The crystal structure and photoluminescence characteristics of the as-prepared sample were investigated in detail. Under the excitation of 408 nm, the optimal CLHAO:0.05Ce3+ green phosphors exhibited a broad emission band in the range of 450–700 nm with a peak at 515 nm. Impressively, the full width at half-maximum (FWHM) of this sample was determined to be about 116 nm, which was much broader than that of commercial (Ba,Sr)2SiO4:Eu2+ green phosphors (FWHM = 67 nm). The internal quantum efficiency of CLHAO:0.05Ce3+ green phosphors was measured to be 46.5%. Finally, by using a 400 nm LED chip and the commercial CaAlSiN3:Eu2+ red phosphors, the as-prepared CLHAO:0.05Ce3+ green phosphors, as well as the BAM:Eu2+ blue phosphors, a package of white light-emitting diode (LED) device was fabricated. Interestingly, under 60 mA current, the white LED device displayed a smooth emission spectrum, without a spectrum cavity in cyan region. And thus the resulting warm white light possessed a high CRI value (Ra) of 92.0, which was greatly better than that of another white LED device fabricated by using commercial (Ba,Sr)2SiO4:Eu2+ green phosphors as color converter (Ra = 80.6). We anticipate that the work presented here may open up new insights for finding high-performance color-converting phosphors for high-CRI solid-state lighting devices.