An efficient blue-excitable broadband YScAlO:Ce garnet phosphor for WLEDs.

Most commercial phosphor-converted white light-emitting diodes (pc-WLEDs) are manufactured with blue LED chips and yellow-emitting YAlO:Ce (YAG:Ce) garnet phosphor, but the lack of blue-green light in the spectrum results in a low color rendering index (CRI). In this paper, we synthesized YScAlO:Ce (YSAG:Ce) by replacing Al in YAG:Ce with Sc. The introduction of Sc with a larger ionic radius through a cation substitution strategy causes lattice expansion, elongation of the Y-O bond, and ultimately a decrease in Ce 5d level crystal field splitting. As a consequence, the emission spectrum undergoes a blue-shift of 10 nm. Furthermore, the YSAG:Ce phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Moreover, the analysis of Eu emission spectra demonstrates that the introduction of Sc resulted in a slight reduction of the dodecahedral lattice symmetry. YSAG:Ce effectively compensates for the lack of the blue-green region, and WLEDs with high color rendering index (90.1), low color temperature (4566 K) and high luminous efficiency (133.59 lm W) were prepared using the combination of YSAG:0.08Ce, CaAlSiN:Eu and 450 nm blue chips. These findings indicate that YSAG:Ce garnet phosphor has potential to be used in high quality WLEDs.