Journal of Luminescence最新文献

With the continuous increase in research and market demand for display, Micro-light-emitting diode (Micro-LED) has become one of the current research hotspots in the display industry due to its outstanding performance in color, resolution, life, and energy consumption. In this study, all-inorganic perovskite quantum dots (QDs) were synthesized using a hot injection method and uniformly coated on the surface of a polyethylene terephthalate (PET) substrate. Subsequently, laser processing technology was used to pattern the QDs film, achieving precise pattern design. Even after bending the film 100 times, the peak intensity of photoluminescence could still reach over 50 % compared with that of unbending. We used these specially treated flexible QDs films as the color conversion layers to realize color conversion display of Micro-LED. This research provides a research direction for the development of new display technology.

New single phase and adjustable emission phosphors have attracted a lot of attention because of the good luminous properties. In this work, Sm³⁺ doped CaTbAl₃O₇ phosphors are prepared in air by solid-state method. The crystal structure, concentration dependent spectra, lifetimes, and luminescence properties are investigated. Because of the 4f⁸ → 4f⁷5d¹ and 4f → 4f transitions of Tb³⁺ ion, host (CaTbAl₃O₇) shows an excitation spectrum in the range of 220–520 nm under monitored at 544 nm and emits yellow-green light under excitation 248, 284, and 368 nm due to the ⁵D₄ → ⁷F_J (J = 0, 1, 2, 3, 4, 5, and 6) transitions of Tb³⁺ ion. CaTbAl₃O₇:Sm³⁺ under monitored 598 nm contains the excitation spectral peaks of both CaTbAl₃O₇ and Sm³⁺ ion. With excitation at 368 nm, CaTbAl₃O₇:Sm³⁺ glows orange-red light, its PL spectrum has both host (CaTbAl₃O₇) and Sm³⁺ ion contributing, and the chromaticity coordinates are about (0.5499, 0.4351). Under excitation 402 nm, the red-orange emission of CaTbAl₃O₇:Sm³⁺ is only the contribution of Sm³⁺ ion and the chromaticity coordinates are about (0.5823, 0.4168). The energy transfer process from Tb³⁺ in host (CaTbAl₃O₇) to Sm³⁺ ions can be confirmed via the spectral properties. We explain the luminous mechanism of CaTbAl₃O₇:Sm³⁺ by the energy level diagrams of Tb³⁺ and Sm³⁺.

In this paper, a novel far-red emitting garnet-structured phosphor, Y₃Ga₃MgSiO₁₂:Mn⁴⁺, was synthesized using the traditional solid-state reaction method. The prepared Y₃Ga₃MgSiO₁₂:Mn⁴⁺ phosphor exhibits a broad excitation band in the range of 250–600 nm and emits bright far-red light in the wavelength range of 630–710 nm, with a peak at 670 nm when excited at 354 nm. The optimal doping concentration of Mn⁴⁺ is approximately x = 0.006. Beyond this concentration, luminescence quenching occurs due to energy transfer between Mn⁴⁺ ions caused by dipole-dipole interactions. The effect of cation substitution on the photoluminescence properties of Y₃Ga₃MgSi_(1-y)Ge_yO₁₂:0.01Mn⁴⁺ phosphors was studied, revealing that the substitution of Ge⁴⁺ ions can systematically influence the luminescence of Mn⁴⁺. The Y₃Ga₃MgSiO₁₂:0.01Mn⁴⁺ phosphor exhibits excellent color purity, and its emission spectrum matches well with the absorption spectra of photosensitive pigments P_R and P_FR. The temperature-dependent emission spectra of Y₃Ga₃MgSi_(1-y)Ge_yO₁₂:0.01Mn⁴⁺ phosphors were studied, and the activation energy was calculated. The substitution of Ge⁴⁺ ions can improve the thermal stability of the samples. These outstanding photoluminescence properties suggest that Y₃Ga₃MgSiO₁₂:Mn⁴⁺ phosphor has application potential in pc-WLEDs and indoor plant cultivation pc-RLEDs. The findings of this work provide ideas for the design of high performance Mn⁴⁺ activated phosphors.

Photon avalanche is a special phenomenon of upconversion that the luminescence emission intensity exhibits a significant nonlinear response to the excitation power. Traditional photon avalanche is typically observed in bulk materials, which is not enough to meet requirements of modern techniques as it expect smaller in size and stronger in signal response. In this study, photon avalanche effect is obtained from single LiYF₄: Yb³⁺/Pr³⁺ microparticle. The emission intensity demonstrates a 16-order nonlinear coefficient with excitation intensity change under 835 nm laser excitation. By utilizing the plasmonic effect of noble metal nanoparticles, we successfully modulate the photon avalanche of the particle. Obvious reduction in the threshold of photon avalanche is detected when plasmonic gold nanorods are assembled to the surface of LiYF₄: Yb³⁺/Pr³⁺ microparticle.

The exploration of efficient narrowband emission phosphors is crucial for white light-emitting diodes (WLEDs) in high-performance backlighting applications. Up to now, the discovery of narrow-band Bi³⁺-doped phosphors for emerging applications remains challenging because Bi³⁺ typically exhibits broadband emission properties. A novel narrow-band blue phosphor (Ca₄SnGe₃O₁₂:Bi³⁺) was successfully synthesized, benefiting from the highly symmetric crystal environment and tightly connected rigid structure of the garnet structure. The phosphor demonstrates broad excitation in the near-ultraviolet (n-UV) region and emits narrowband blue light at 442 nm (FWHM = 36 nm) with a color purity of 94.7 %. In this paper, the assignment of different luminescence centers and the use of Zr/Hf to partially replace Sn to enhance luminescence performance are studied. The reasons for the consequent changes in luminescence behavior are explained in detail. The use of narrowband commercial red K₂SiF₆:Mn⁴⁺, green β-Sialon:Eu²⁺, and synthetic blue luminescent materials as RGB emitters covered 81 % of the National Television System Committee (NTSC) color space, demonstrating great potential for liquid-crystal-display (LCD) backlight use.

Trivalent terbium ion doped lanthanum tungstate (La_2-xTb_x(WO₄)₃; x = 0.6,1.0,1.4) and terbium tungstate (Tb₂(WO₄)₃) phosphors were successfully synthesized via optimized microwave-assisted co-precipitation technique. The phase purity and crystallinity of the prepared samples were confirmed using the powder XRD technique. The photoluminescence studies revealed a quenching-free emission up to 70 % of Tb³⁺ doping concentration, even though the emission intensity slightly decreases under host excitation since it becomes less relevant at higher doping concentrations. The experimental and calculated oscillator strengths were evaluated using absorption data and further used to quantify the Judd - Ofelt (JO) intensity parameters, which appeared in a trend of Ω₂>Ω₄>Ω₆ for all samples. As a theoretical approach to assure the excellency of the tungstate host, the radiative parameters were calculated from the emission data using the JO analysis technique. The dominance in the values of stimulated emission cross section and gain bandwidth corresponding to ⁵D₄→⁷F₅ transition of Tb³⁺ ion of lanthanum tungstate proclaims it as an excellent green phosphor. Hence, the less susceptibility of the tungstate host towards concentration quenching is confirmed in the present work.

Pristine and europium doped calcium magnesium silicate (CMS and CMS: Eu³⁺) phosphor having akermanite (Ca₂MgSi₂O₇), monticellite (CaMgSiO₄) and merwinite (Ca₃MgSi₂O₈) phases are synthesized via solid state reaction method. The modification of photoluminescence properties such as emission intensity, decay time and quantum yield (QY) due to the variation of the crystal structure, local site symmetry and coordination geometry of akermanite, monticellite and merwinite phases are studied. The merwinite phase is optimized at an annealing temperature of 900 °C, whereas monticellite phase is at 1100 °C. The agglomerated morphology changes to particle formation as the annealing temperature changes from 900 °C to 1100 °C. The lattice parameters and site preference of Eu³⁺ ions are determined using Density Functional Theory (DFT) calculations. The analysis of lattice expansion, formation enthalpy (${\Delta H}_f$) and mixing energy (${\Delta H}_m$) reveal the preference of Eu³⁺ occupation in the Ca²⁺ cationic site over Mg²⁺ for all three phases. The blueshift and redshift of Mg-O and Ca-O stretching in the Fourier Transform Infra-Red (FTIR) analysis agree with the DFT calculation. UV–visible spectra analyses reveal a modification in optical bandgap with Eu³⁺ addition. The highest intensity ⁵D₀→⁷F₂ induced electric dipole (ED), hypersensitive transition indicates the preference of Eu³⁺ ions in a non-inversion center for all the phases. This agrees with the higher ${\Omega }_2$ values from Judd-Ofelt (J-O) parameter calculations and local site symmetry analysis of DFT-optimized structures. The monticellite phase exhibits maximum crystal field splitting due to its octahedral geometry, whereas the akermanite phase, with its distinct dodecahedral geometry, displays maximum emission intensity, an extended decay time, and the highest quantum yield (QY). The modification of photoluminescence properties of the three phases is analyzed in detail based on the coordination geometry and the distortion in local sites due to Eu³⁺ doping in the Ca and Mg sites. CIE color chromaticity analysis confirms the orange-red emission with 91.94 %, 90.88 % and 90.24 % color purity for akermanite, monticellite and merwinite phases respectively. Hence, the present study throws light on the potency of the akermanite phase of CMS: Eu³⁺ phosphor with 70 % QY as the optimal matrix for Eu³⁺ ions over monticellite and merwinite host matrices.