Red phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). However, the development of a red phosphor with simultaneous high efficiency, excellent thermal stability and high colour purity is still a challenge. In this work, unique non-concentration quenching in solid-solution Cs3Gd1 − xGe3O9:xEu3+ (CGGO:xEu3+) (x = 0.1–1.0) phosphors is successfully developed to achieve a highly efficient red-emitting Cs3EuGe3O9 (CEGO) phosphor. Under the optimal 464 nm blue light excitation, CEGO shows a strong red emission at 611 nm with a high colour purity of 95.07% and a high internal quantum efficiency of 94%. Impressively, this red-emitting CEGO phosphor exhibits a better thermal stability at higher temperatures (175–250 °C, >90%) than typical red K2SiF6:Mn4+ and Y2O3:Eu3+ phosphors, and has a remarkable volumetric negative thermal expansion (coefficient of thermal expansion, α = −5.06 × 10−5/°C, 25–250 °C). By employing this red CEGO phosphor, a fabricated pc-WLED emits warm white light with colour coordinates (0.364, 0.383), a high colour rendering index (CRI = 89.7), and a low colour coordinate temperature (CCT = 4508 K). These results indicate that this highly efficient red-emitting phosphor has great potential as a red component for pc-WLEDs, opening a new perspective for developing new phosphor materials. A luminescent material that undergoes an unusual heat-shrinking process shows promise for enhancing the efficiency of white light-emitting diodes (LEDs). Current technologies for generating white LEDs often combine near-ultraviolet light with background radiation from red, green, and blue phosphors. J.L. from China’s Changchun Institute of Applied Chemistry and colleagues have now developed a red phosphor that remains active at temperatures which shut down other red-light emitters. The team’s compound, a cesium-based metal oxide doped with rare earth ions, has a crystal structure that contracts upon heating and avoids symmetry-distorting effects associated with thermal quenching. This unique structure also supports higher dopant concentrations than typical phosphors for improved colour rendering in prototype white LEDs. A highly efficient red-emitting Cs3EuGe3O9 phosphor for high-performance pc-WLEDs is discovered with non-concentration quenching, favourable thermal stability, high colour purity and negative thermal expansion.

/pdf/thermally-stable-and-highly-efficient-red-emitting-eu3-doped-3epdl74b4d.pdf

Thermally stable and highly efficient red-emitting Eu3+-doped Cs3GdGe3O9 phosphors for WLEDs: non-concentration quenching and negative thermal expansion.

A red phosphor LaSc3(BO3)4:Eu3+ with zero-thermal-quenching and high quantum efficiency for LEDs

Excellent photoluminescence and cathodoluminescence properties in Eu3+-activated Sr2LaNbO6 materials for multifunctional applications

Replacing traditional luminous silicone or resins with phosphor in ceramics (PiCs) as color converters has been proposed as an efficient way to improve thermal stability of high-power white light-emitting diodes (WLEDs). However, excessive light scattering in existing PiCs results in enormous phosphor-converted light losses, which makes the luminosity of current PiCs color converters less efficient and means that they can only be used in devices working in reflective mode. By introducing nano wave plate structuring and Rayleigh scattering, luminous hydroxyapatite (HA)-YAG: Ce ceramics are prepared from mesoporous HA nanorods and YAG: Ce phosphors at 850 °C, enabling for the first time WLEDs equipped with PiC color converters in transmission mode. With low-temperature sintering and a highly transparent matrix, the quantum yield of HA-YAG: Ce retains ≈90% of the raw phosphor, and WLEDs with the color converters exhibit a record luminous efficiency of 170 lm W-1 and a correlated color temperature below 4500 K. A facile and practical strategy of using nano structural modulation to eliminate birefringence-induced light scattering for fabricating high-performance ceramic converters suitable for multiple mode luminaires is demonstrated.

Nano Wave Plates Structuring and Index Matching in Transparent Hydroxyapatite-YAG: Ce Composite Ceramics for High Luminous Efficiency White Light-Emitting Diodes.

Enhanced local symmetry achieved zero-thermal-quenching luminescence characteristic in the Ca2InSbO6:Sm3+ phosphors for w-LEDs

A novel red phosphor Ba2La4Y4(SiO4)6O2:Eu3+ with high quantum yield and thermal stability for warm white LEDs

Recent progress in ceramic matrix composites reinforced with graphene nanoplatelets

Facile synthesis of mesoporous WO3@graphene aerogel nanocomposites for low-temperature acetone sensing

Mesoporous silica SBA-15 encapsulated with Au nanoparticles was consolidated by spark plasma sintering. It turned out to be an original and facile preparation route for incorporating Au nanoparticles in silica glass. The incorporation of Au nanoparticles in a silica glass matrix made the obtained glass coloured dark wine-red due to the surface plasmon resonance effect of Au nanoparticles, although the concentration of Au nanoparticles was extremely low (about 0.05 wt%). Besides, the Z-scan method using a femtosecond laser pulse was employed to measure the nonlinear optical property of this mesoporous composite-derived glass, which exhibited self-focusing feature at 720 nm with saturable absorption. The third-order nonlinear refraction index n2 and absorption coefficient β were 1.74 × 10−18 m2 W−1 and −5.72 × 10−12 m W−1, respectively. We believe that this approach could be extended to disperse other metal or semiconductor nanoparticles in a glass matrix.

Xin Zhang

Papers

A red phosphor LaSc3(BO3)4:Eu3+ with zero-thermal-quenching and high quantum efficiency for LEDs

A novel red phosphor Ba2La4Y4(SiO4)6O2:Eu3+ with high quantum yield and thermal stability for warm white LEDs

Recent progress in ceramic matrix composites reinforced with graphene nanoplatelets

Facile synthesis of mesoporous WO3@graphene aerogel nanocomposites for low-temperature acetone sensing

Third-order nonlinear optical vitreous material derived from mesoporous silica incorporated with Au nanoparticles