Cyan-Green Phosphor (Lu₂M)(Al₄Si)O₁₂:Ce³⁺ for High-Quality LED Lamp: Tunable Photoluminescence Properties and Enhanced Thermal Stability

Abstract

High-quality white light-emitting diodes (w-LEDs) are mainly determined by conversion phosphors and the enhancement of cyan component that dominates the high color rendering index. New phosphors (Lu 2 M)(Al 4 Si)O 12 :Ce 3+ (M = Mg, Ca, Sr and Ba), showing a cyan-green emission, have been achieved via the co-substitution of Lu 3+ -Al 3+ by M 2+ -Si 4+ pair in Lu 3 Al 5 O 12 :Ce 3+ to compensate for the lack of cyan region and avoid using multiple phosphors. The excitation bands of (Lu 2 M)-(Al 4 Si)O 12 :Ce 3+ (M = Mg, Ca, Sr and Ba) show a red-shift from 434 to 445 nm which is attributed to the larger centroid shift and crystal field splitting. The enhanced structural rigidity associated with the accommodation of larger M 2+ leads to a decreasing Stokes shift and the corresponding blue-shift (533 → 511 nm) in emission spectra, along with an improvement in thermal stability (keeping ∼93% at 150 °C). The cyan-green phosphor Lu 2 BaAl 4 SiO 12 :Ce 3+ enables to fabricate a superhigh color rendering w-LED (R a = 96.6), verifying its superiority and application prospect in high-quality solid-state lightings.

Highly efficient yellow‐orange emission and superior thermal stability of Ba2YAl3Si2O12:Ce3+ for high‐power solid lighting

“…The peculiar garnet structure is found to offer a remarkable flexibility in accommodating various cations to change the crystal filed strength and the covalency of Ce 3+ -O 2− , which could bring various emission spectra covering green to orange region. [13][14][15][16][17][18][19] In previous studies, 20,21 co-substitution design strategy is very important to improve the luminescence performance of materials. Cosubstitution is the two or more ions simultaneous replacement in the original structure to form a new isomorphic material.…”

“…17 Meanwhile, they also obtained a series of cyan-green phosphors Lu 2 M(Al 4 Si)O 12 :Ce 3+ (M = alkaline earth), in which the incorporation of M 2+ -Si 4+ pair into LuAG:Ce 3+ gives rise to a blue-shift. 15 Ji et al discovered some new candidates named Y 2 MAl 4 SiO 12 :Ce (M = Mg, Ca, Sr, Ba) for yellow phosphor, which exhibit blue-shift from 552 to 534 nm with the atomic number of M increasing. 1 As a consequence, warm w-LEDs with lower correlated color temperature (CCT) and better color rendering index (CRI) is expected to be gained by modifying the typical garnet composition.…”

A novel green‐emitting luminescent materials with broad‐band emission for high‐quality warm white LED indoor lighting

“…In order to further investigate the energy transfer among the Ce 3+ , the series of decay curves of the samples with different Ce 3+ concentration were measured at room temperature as shown in Figure 6. And all the decay curves can be fitted well by the single exponential equation: 22,40 where the value of A is constant, while the t and τ are time and lifetime, respectively. As expected, one notices that the lifetime continuously decreases following the increase in Ce 3+ concentration from 0.03 to 0.25.…”

“…Unfortunately, there is little Ce 3+ ‐doped garnet structure phosphor can emit efficient cyan‐green light which can cover from blue to green‐yellow regions under n‐UV excitation. Although some cyan‐emitting phosphors have been prepared such as BaSi 2 O 2 N 2 : Eu 2+ , 21 (Lu 2 M)(Al 4 Si)O 12 : Ce 3+ (M = Mg, Ca, Sr and Ba), 22 Ca 2 LuHf 2 (AlO 4 ) 3 : Ce 3+ , 23 K 2 HfS i3 O 9 : Eu 2+ , 24 Ca 3 Hf 2 SiAl 2 O 12 , 25 Ca 2 YHf 2 Al 3 O 12 , 26 and so on, their shortcomings are also nonnegligible, such as harsh synthesis conditions, poor quantum efficiency, and not broad emission spectrum, which are restricted for their extensive application in high‐quality warm white LED. Thus it is meaningful to explore efficient green phosphor with broad cyan‐green emission under n‐UV excitation for high‐quality warm white LED.…”

Sr‐induced color‐tunable and thermal stability enhancing in the phosphor (Ba1‐xSrx)9Lu2Si6O24:Eu2+ for solid‐state lighting

“…However, YAG:Ce 3+ has some obvious disadvantages, for instance, lacking of a red component causes to cool white light and poor thermal stability at high temperature. Now the main commercial WLED technology is based on a blue chip, Y 3 Al 5 O 12 :Ce 3+ yellow phosphors and (Ca, Sr)AlSiN 3 :Eu 2+ red phosphors . In recent years, the WLED combined with ultraviolet (UV) LED chip and three‐primary color (red, green, and blue) phosphors draw much attention because they can achieve an ideal white light that have a high CRI and appropriate CCT.…”