Thermally stable La2LiSbO6:Mn4+,Mg2+far-red emitting phosphors with over 90% internal quantum efficiency for plant growth LEDs

Broadband La2LiSbO6: Cr3+ Phosphors with Double Luminescent Centers for NIR pc-LEDs

The La2LiSbO6: xCr3+ phosphors were synthesized by means of a high-temperature solid-phase method. Based on the differences in ionic radius, valence state, and formation energy, the substitution sites of Cr3+ ions are discussed in detail. The optimized doping concentration of Cr3+ is determined to be 0.01. Under 517 nm excitation, the La2LiSbO6: 0.01Cr3+ phosphor presents a wide emission band (from 700 to 1350 nm) with a peak centered at 952 nm. Additionally, its corresponding full width at half-maximum is 155 nm, and the internal quantum efficiency reaches 62.4%. Meanwhile, the emission intensity of the La2LiSbO6: 0.01Cr3+ phosphor at 373 K is about 63.7% of that at room temperature, exhibiting good thermal stability. Aiming to fabricate a near-infrared phosphor-converted light-emitting diode device, the La2LiSbO6: 0.01Cr3+ phosphor is mixed with epoxy adhesive and cured on a green light-emitting diode chip. Under the irradiation of the fabricated light-emitting diode device, fruits and writing in the dark environment can be captured by a near-infrared camera. Hence, the La2LiSbO6: 0.01Cr3+ phosphor is promising for night vision.

Lumino-structural properties of Dy3+ activated Na3Ba2LaNb10O30 phosphors with enhanced internal quantum yield for w-LEDs

With an intend to develop white light emitting phosphor, for w-LED application, a series of dysprosium (Dy³⁺) doped novel Na₃Ba₂LaNb₁₀O₃₀ phosphors were prepared using solid state reaction technique at 1300 °C. Their structural, morphological and vibrational spectroscopic analysis was performed. We illustrate the luminescence characteristics of the prepared phosphors for various Dy³⁺ ion doping concentration. The XRD analysis demonstrates that the prepared phosphors were in single phase, and of tetragonal tungsten bronze structure of the P4bm space group. The FE-SEM image reveals that the prepared phosphors contained irregular shaped both nano and micro particles. Under near-ultraviolet (n-UV) irradiation at 387 nm, the photoluminescence (PL) emission spectra shows three characteristic bands at 481 nm (blue), 575 nm (yellow) and 666 nm (red). Obtained optimized Dy³⁺ ion concentration for the prepared sample is 7.0 mol%, beyond which the concentration quenching begins. Bonding between Dy-O is covalent in nature as confirmed by bonding parameters and the Dexter theory revealed that the energy transfer among Dy³⁺ ions is dipole-diploe interaction. CIE chromaticity coordinates, CCT and color purity confirms the formation of warm white light emitting phosphors. Lifetime analysis demonstrates the longer decay time in the phosphors. The Internal Quantum Yield (IQE) and brightness (B) for the optimised phosphor is calculated as 45.35% and 11.41% respectively, which makes it a suitable phosphor for w-LED.

Fluorescence Lifetime-Based Luminescent Thermometry Material with Lifetime Varying over a Factor of 50

Recently, the growing demand for temperature detection is pushing forward the flourishing development of noncontact optical thermometry. Herein, a new red phosphor Sr₂InTa_1-xO₆:xMn⁴⁺ (SIT:xMn⁴⁺) was first constructed and systematically investigated. Based on the fairly rapid decline of the lifetime from 0.403 to 0.008 ms by increasing the temperature from 25 to 450 K, a noncontact optical thermometer can be made from phosphor SIT:0.003Mn⁴⁺ with S_r = 1.396% K^-1 at 375 K and S_a = 0.0012 K^-1 at 300 K. Because the luminescence is based on the outermost 3d orbits of Mn⁴⁺, the lifetime of SIT:xMn⁴⁺ is quite sensitive to the temperature, leading to a rapid decline of the lifetime with the increase in temperature. Moreover, multiple rounds of variable-temperature studies were performed to demonstrate the stability and reversibility of SIT:0.003Mn⁴⁺. This work suggests that Mn⁴⁺-phosphors are promising candidates for application as optical thermometric material.

Enhanced photoluminescence and energy transfer performance of Y3Al4GaO12:Mn4+,Dy3+ phosphors for plant growth LED lights

Plant growth LEDs have attracted broad attention in modern society, desperate for specific phosphors with a characteristic emission band. A novel Mn⁴⁺ and Dy³⁺ co-doped Y₃Al₄GaO₁₂ phosphor were successfully prepared through a conventional high-temperature solid-state reaction. A three band emission including red (625–700 nm), orange (550–607 nm) and blue (462–490 nm) is observed in these phosphors when excited under a near-UV lamp, which is ascribed to ²E → ⁴A₂ of Mn⁴⁺, ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 of Dy³⁺, respectively. The three emissions match the absorption spectra of chlorophyll A and chlorophyll B well. Meanwhile, the energy transfer from Dy³⁺ to Mn⁴⁺ was confirmed by the luminescence spectra and lifetime analysis. Finally, an LED device was fabricated that consisted of a 365 nm ultraviolet chip and the Y₃Al₄GaO₁₂:Mn⁴⁺,Dy³⁺ phosphor. The excellent properties indicate that the synthesized phosphor has a promising application in the optical agricultural industry.

Enhanced photoluminescence properties and confirmed energy transfer in a YAGO:Mn⁴⁺,Dy³⁺ phosphor.