Synthesis and luminescent properties of Eu3+, Eu3+/Bi3+ and Gd3+ codoped YAG:Ce3+ phosphors and their potential applications in warm white light-emitting diodes

Highly efficient Ce: Lu(Mg,Al)2(Si,Al)3O12 phosphor ceramics for high-power white LEDs/LDs

Lu₃Al₅O₁₂: Ce³⁺ (LuAG: Ce³⁺) phosphor ceramics (PCs) with high quantum efficiency and excellent thermal stability are incredibly promising color converters for high-power white light emitting diodes (LEDs)/ laser diodes (LDs) lighting. However, the greenish emission of LuAG:Ce³⁺ PCs does not allow to reach white light emission upon pumping by a blue LED/ LD without an additional red luminescent material. In this work, a series of (Ce_0.003Lu_0.997)₃(MgxAl_1-2xSix)₅O₁₂ (LCMASG) (x = 0-0.15) PCs were fabricated by solid state reaction method. Impressively, the as-prepared PCs exhibited a distinct red-shift (513→538nm) and a 17% increase of the color index (CRI) of high-power white LED(58.4→70.4). Particularly, Ce: Lu(Mg, Al)₂(Si, Al)₃O₁₂ PC with 15 at.% substitution concentration showed only 8% luminescent intensity loss at 150 °C and high internal quantum efficiency (IQE) of 82%, exhibiting desirable optical thermal stability. By combining with a 460 nm blue chip or a 455 nm laser source, white LED/LD devices based on the LCMASG PCs in a remote excitation mode were constructed. The optimized luminous efficiency of Ce: Lu(Mg, Al)₂(Si, Al)₃O₁₂ PC with 15 at.% Mg²⁺/Si⁴⁺ doping up to 176.4 lm/W was obtained as the power density of the blue laser increased to 6.52 W/mm². Also, a 4053K CCT of the warm white light emission was realized. Therefore, this work proves that the LCMASG PCs are promising to serve as color converters for high power LEDs/LDs lighting in the future.

Luminescence properties and energy transfer of La3Ga5SiO14:Eu3+, Tb3+ phosphors

The La₃Ga₅SiO₁₄ based phosphors were generated by substitutions of Tb³⁺/Eu³⁺ to La³⁺. The Tb³⁺ → Eu³⁺ energy transfer occurs in Tb³⁺/Eu³⁺ codoped phosphors. The La_2.70Eu_0.12Tb_0.18Ga₅Si₁₄ phosphor shows an internal quantum yield about 88.82%.

Luminescence of Tb3Al5O12 phosphors co-doped with Ce3+/Gd3+ for white light-emitting diodes

Tb_{2.96- x} Ce_0.04Gd_xAl₅O₁₂ phosphors were synthesized through solid-state reactions. The influence of Gd³⁺ on the luminescence was investigated. Under the excitation at 460 nm, Tb_2.96Ce_0.04Al₅O₁₂ shows the characteristic emission band of Ce³⁺ with a peak wavelength at about 554 nm. After co-doping Gd³⁺ into Tb_2.96Ce_0.04Al₅O₁₂, the peak wavelength of the Ce³⁺ emission band shifts to longer wavelengths, which is induced by the increasing crystal field splitting. However, the Ce³⁺ emission intensity also decreases because the substitution of Tb³⁺ with Gd³⁺ causes lattice deformation and generates numerous structural and chemical defects. By comparing the light parameters of white light-emitting diodes (WLEDs) containing Y_2.96Ce_0.04Al₅O₁₂, Tb_2.96Ce_0.04Al₅O₁₂ and Tb_2.81Ce_0.04Gd_0.15Al₅O₁₂ phosphors, we can find that the WLED containing the Tb_2.81Ce_0.04Gd_0.15Al₅O₁₂ phosphor generates warmer light than the WLEDs containing Y_2.96Ce_0.04Al₅O₁₂ and Tb_2.96Ce_0.04Al₅O₁₂ phosphors. Moreover, the WLEDs fabricated by integrating a blue LED chip and Ce³⁺/Gd³⁺-co-doped Tb₃Al₅O₁₂ phosphors show outstanding colour stability when driven under different currents.