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 for 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 at 1400 °C calcination temperature and a reducing atmosphere. These CYSAS:Ce³⁺ phosphors crystallize into the garnet phase with the Iad space group, and their crystallographic data are obtained by using the Rietveld refinements. Photoluminescence characterization reveals that the CYSAS:Ce³⁺ phosphors exhibit broadband excitation spectra in the 250–500 nm spectral range with a peak at 452 nm, which matches well with commercial blue LED chips (440–480 nm). The concentration quenching effect is observed for CYSAS:Ce³⁺ phosphors, and the 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 an emission peak at 538 nm and a bandwidth of 121 nm. The corresponding CIE chromaticity coordinates are (0.3662, 0.5446). Notably, luminescence quantum efficiency (QE) measurements demonstrate that the CYSAS:4%Ce³⁺ sample has an excellent internal QE of 91.1% and an external QE of 51.7%. In addition, temperature-dependent emission properties indicate its good thermal stability (66%@150 °C) and good color stability (chromaticity shift ΔE = 3.15 × 10⁻³) for the CYSAS:4%Ce³⁺ phosphor. By combining the CYSAS:4%Ce³⁺ green phosphor with the 450 nm blue chip and the (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 a high color rendering index (92.6), low correlated color temperature (4726 K), and high luminous efficacy (109.89 lm W⁻¹). In summary, the above results show that the 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.