High-performance green-emitting Ca2YScAl2Si2O12:Ce3+ garnet phosphors and their applications in high-quality blue-chip-pumped white LEDs

Abstract

Green phosphors have attracted much attention in recent years due to their great potential in achieving high-quality white light-emitting diode (LED) lighting. Herein, we report the discovery and characterization of a novel green-emitting Ca2YScAl2Si2O12:Ce3+ (abbreviated as CYSAS:Ce3+) garnet-type inorganic phosphor showing outstanding photoluminescence features. A family of CYSAS:Ce3+ samples are intentionally incorporated with different Ce3+ doping concentrations ranging from 1 mol% to 8 mol%, and they were successfully prepared by using the conventional high-temperature solid-state reaction method with 1400 oC calcination temperature and reducing atmosphere. These CYSAS:Ce3+ phosphors crystallize into garnet phase with Ia3 @#x0305;d space group, and their crystallographic data are obtained by using the Rietveld refinements. Photoluminescence characterizations reveal that the CYSAS:Ce3+ phosphors exhibit broadband excitation spectra in the 250-500 nm spectral range peaking at 452 nm, which matches well with commercial blue LED chips (440-480 nm). Concentration quenching effect is observed for CYSAS:Ce3+ phosphors, and related mechanism has been discussed. In particular, under 452 nm excitation, the optimal CYSAS:4%Ce3+ sample produces a broad, asymmetric, green emission band in the 470-750 nm wavelength range with emission peak at 538 nm and bandwidth of 121 nm. The corresponding CIE chromaticity coordinates are located at (0.3662, 0.5446). Notably, luminescence quantum efficiency (QE) measurement demonstrate that the CYSAS:4%Ce3+ sample has excellent internal QE of 91.1% and external QE of 51.7%. In addition, temperature-dependent emission properties indicate its good thermal stability (66%@150 oC) and good color stability (chromaticity shift ΔE = 3.15 × 10-3) for CYSAS:4%Ce3+ phosphor. By combining CYSAS:4%Ce3+ green phosphor with 450 nm blue chip and (Ca,Sr)AlSiN3:Eu2+ commercial red phosphor, a white LED device with excellent light efficiency and high light color quality was fabricated. When the driving current is 20 mA, the LED device exhibits high CRI (92.6), low CCT (4726 K), and high LE (109.89 lm W-1). In summary, the above results show that CYSAS:Ce3+ phosphor has great application potential in achieving high-quality white LEDs, and it also provides a new exploration idea for the development of new green-emitting phosphors.