photoluminescence properties of Yb~(2+) in CaAlSiN3 as a novel red-emitting phosphor for white LEDs

摘要

This paper reports on the diffuse reflection spectra, photoluminescence spectra and chromaticity of ytterbium in CaAlSiN3 at room temperature. It can be excited efficiently over a broad spectral range between 280 and 580 nm and exhibits a single intense red emission at 629 nm with a full width at half maximum of 75 nm due to the electronic transitions from the excited state of 4f~(13)5d to the ground state 4f~(14) of Yb~(2+).Thelow energy of Yb~(2+) emission in CaAlSiN3 can be attributed to the large nephelauxetic effect and crystal field splitting due to the coordination of Yb~(2+) by nitrogen. This novel developed CaAlSiN3:Yb~(2+), which is the first Yb~(2+)-activated nitride red-emitting phosphor, has potential applications in spectral conversion materials for warm-white LEDs. The width of the emission band, Stokes shift and thermal quenching mechanism of Yb~(2+) in CaAlSiN3 and (oxy)nitride-based phosphors are discussed and compared with those of Eu~(2+).