Insight into the crystal structure and photoluminescence properties of an extremely broadband yellow-emitting phosphor Sr8MgCe(PO4)(7):Eu2+

The combination of binary complementary color phosphors with near-ultraviolet (NUV) light-emitting diode (LED) chips was put forward to lower the energy loss caused by the reabsorption of the combination of tricolor phosphors with NUV LED chips. Thus investigating broadband yellow-emitting phosphors with enriched red components in the spectral range has gained much attention. Here, an extremely broadband yellow-emitting phosphor Sr8MgCe(PO4)(7):Eu2+ with sufficient red component in the spectral region was synthesized. Due to the introduction of Ce into the host, Sr8MgCe(PO4)(7) shows an emission band with a peak at 375 nm when excited at 310 nm. Meanwhile, Eu2+ doped Sr8MgCe(PO4)(7) exhibits an extremely broad yellow emission band with a full width at half-maximum of 175 nm and a peak located at about 598 nm, due to the 5d-4f transitions of Eu2+ ions substituting five Sr2+ sites. The excitation peak of the host at 310 nm was detected in the excitation spectrum of Sr8MgCe(PO4)(7):Eu2+ monitored at 598 nm, indicating the energy transfer from the host to Eu2+, which was also proved by the decay curves. On the other hand, the excitation band at about 400 nm due to the 4f-5d transitions of Eu2+ was also detected in the excitation spectrum of Sr8MgCe(PO4)(7):Eu2+, and this matches well with the NUV LED chips. Moreover, the energy transfer between Eu2+ ions at different crystallographic sites was demonstrated by time-resolved photoluminescence (TRPL) spectra. A white LED with a CRI (R-a) of 82.88 and a CCT of 4238 K was prepared through a 400 nm NUV LED chip, Sr8MgCe(PO4)(7):Eu2+ and BaMgAl10O17:Eu2+ (BAM:Eu2+). These results pave the way for designing better Eu2+-doped phosphors for NUV WLEDs with binary complementary color phosphors.

Automated summary

The study synthesized Sr8MgCe(PO4)7:Eu2+ phosphor with a wide yellow emission band and demonstrated its emission characteristics in the spectral range. The phosphor matched well with the excitation spectrum of NUV LED chips and showed energy transfer between Eu2+ ions at different crystallographic sites through time-resolved photoluminescence spectra.