Crystal configuration, spectroscopic and optical characteristics of Er3+ doped YAlO3 perovskites for advanced photonic appliances

Computational and optoelectronic investigations of red-emissive europium (III) β-diketonate with n-donor ligands for display applications

Europium complexes exhibiting red luminescence were prepared by employing β-diketone as main ligand and 1,10-phenanthroline as an additional ligand. Various methods, including 1H NMR, IR spectroscopy and analysis of optical band gap were employed to examine these complexes. The luminescent photophysical properties were investigated using PL spectroscopy and theoretical calculations were conducted to explore radiative transitions probabilities and Judd-Ofelt (J-O) parameters for transitions of type 5D0 → 7F2, 4. J-O parameters were determined using the JOES computer program and results were in good agreement with the outcomes obtained experimentally. The luminescence analysis results have verified the vibrant, single-color red emission of the prepared complexes. The band gap of ternary europium complexes, determined optically, electronically, and theoretically, falls within the range of 3-4 eV. This similarity indicates that these complexes are potentially suitable as semiconductor materials. The results from absorption, electrochemical and photophysical analyses indicate the potential use of synthesized complexes in lighting and display applications.

Realization of a green-emitting pyrosilicate-structured Er3+-activated Y2Si2O7 phosphor: a systematic study of opto-electronic characteristics and thermal stability for lighting applications

A series of green-emitting Y2-x Si2O7:xEr3+ phosphors (x = 1-7 mol%) have been successfully synthesized using a straightforward gel-combustion method facilitated by urea. X-ray diffraction analysis provided specific patterns for samples, confirming a consistent triclinic phase across erbium-doped structures compared to undoped structures. Studies using TEM and EDX were conducted to identify the surface-related characteristics and chemical composition of the synthesized nanophosphor, respectively. The band gap was determined to be 5.55 eV and 5.80 eV for the host material and optimal sample, respectively. The primary peak of excitation, observed at 379 nm, represents the highly sensitive electric dipole transition from the 4I15/2 state to the 4G11/2 level, suggesting that the prepared phosphors could effectively absorb NUV light for activation. The PL profiles of Y2-x Si2O7:xEr3+ (x = 1-7 mol%) phosphors demonstrate characteristic emissions at 409 nm (2H9/2 → 4I15/2), 522 nm (2H11/2 → 4I15/2), 553 nm (4S3/2 → 4I15/2) and 662 nm (4F9/2 → 4I15/2). In accordance with Dexter's theory, luminescence quenching observed at a concentration of 4 mol% Er3+ is attributed to dipole-quadrupole interactions. The optimal sample demonstrates excellent thermal stability, indicated by its luminescence at different temperatures and activation energy of 0.2641 eV. Additionally, the CIE, color purity and CCT values of the fabricated nanomaterials make it ideal for use in lighting applications.

Cool green-emissive Y2Si2O7:Tb3+ nanophosphor: auto-combustion synthesis and structural and photoluminescence characteristics with good thermal stability for lighting applications

A cheap, versatile, sustainable and energy-efficient gel-combustion method was applied to develop a series of green-emitting down-converted Y2Si2O7:Tb3+ (YPS:Tb3+) nanophosphors. Employing XRD-based Rietveld refinement approach, the phase purity and crystallographic evaluation of the produced phosphor were conducted, revealing a triclinic crystal with P1̄ space group. EDX and TEM analyses were performed on the synthesized samples to determine their elemental composition and morphological properties. Diffuse reflectance spectra yielded 5.61 eV and 5.79 eV optical energy band gaps for the host and the optimized (0.04 mole of Tb3+) sample, respectively. UV light has the ability to excite the nanocrystalline phosphor in an efficient manner, leading to significant luminosity qualities attributed to the radiative relaxation of 5D4 → 7FJ (J = 6, 5, 4, 3). The bi-exponential decay function was derived by the PL decay curves. With an activation energy of 0.2206 eV, the Y1.96Si2O7:0.04Tb3+ phosphor exhibits good thermal quenching capabilities. Improved photometric attributes including CIE coordinates, CCT and color purity confirmed the green glow, indicating a strong competitor for cool-green emission in lighting applications.

A green light emissive LaSr2AlO5:Er3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability

The present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green luminous Er3+ doped LaSr2AlO5 phosphor that was produced by employing an efficient and reliable gel-combustion process assisted with urea as a fuel. Using Rietveld refinement of diffraction data, the crystal structure and phase formation were examined. The surface morphology and elemental configuration of the phosphor were analyzed via TEM and EDX spectroscopy, respectively. The band gap of LaSr2AlO5 (5.97 eV) and optimized La0.96Sr2AlO5:4 mol% Er3+ (5.51 eV) classify the optimized sample as a direct band-gap material. The PL peaks located in the visible range corresponding to transitions 2H9/2 → 4I15/2 (406 nm), 2H11/2 → 4I15/2 (520 nm), 4S3/2 → 4I15/2 (550 nm), and 4F9/ 2 → 4I15/2 (665 nm) were revealed by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er3+ doping, concentration quenching was observed, which was controlled by the quadrupole-quadrupole interaction. Based on the findings of the double exponential fitting of lifetime curves acquired from the emission spectra at λex = 377 nm and λem = 550 nm, the average lifetime of the excited levels of considered nanomaterials was estimated. The temperature-dependent emission spectra of the La0.96Sr2AlO5:4 mol% Er3+ sample were collected in the range 298-498 K. The considered phosphor was found to have a high thermal stability as evidenced by the luminous intensity being sustained at 74.29% at 498 K compared to the intensity at ambient temperature (298 K) with an activation energy of 0.1453 eV. The calculated color purity and superb chromaticity coordinates indicates that the phosphors have a high degree of color purity, which further supports its applicability as a green component in solid-state lighting.

Structural, morphological, and optical characteristics of Gd2 Si2 O7 :Dy3+ nanophosphors for WLEDs

Yellowish-white light-emitting Gd2-x Si2 O7 :xDy3+ (x = 1-5 mol%) nanophosphors were prepared using a solution combustion synthesis method. Fluorescence spectrophotometry and X-ray diffraction measurements were performed to scrutinize the optical performances and phase recognition of the designated nanophosphors. The outcomes specified that the prepared phosphors were crystallized into a triclinic phase with a P-1 space group. As the concentration of Dy3+ ions was increased, the unit-cell volume decrease proportionally due to the replacement of large-sized Gd3+ by small-sized Dy3+ ions. Under ultraviolet excitation at 349 nm, emission spectra consisted of two pronounced emission lines at ~482 nm (blue line), ~578 nm (yellow line), and a relatively weaker emission at ~670 nm (red line) due to 4 F9/2 →6 H15/2 , 4 F9/2 →6 H13/2 , and 4 F9/2 →6 H11/2 intraconfigurational transitions of Dy3+ ions, respectively. The evidence about the site symmetry around Dy3+ ions was examined by considering the ratio of yellow-to-blue emission intensity. The observed critical distance (Rc ) value was ~20.56 Å (≫5 Å), which signified that energy transfer primarily occurred due to multipolar interaction. The obtained coordinates were close to the white region of the Commission Internationale de l'Éclairage chromaticity diagram, which marked a significant milestone in the development of white light-emitting diodes.

Combustion derived single phase Y4Al2O9:Tb3+ nanophosphor: crystal chemistry and optical analysis for solid state lighting applications

Cool green light emanating monoclinic Y_4-x Al₂O₉:xTb³⁺ (x = 1-5 mol%) nanophosphors have been fabricated through gel-combustion method. X-ray diffraction and transmission electron-microscopy data have been utilized to assess their structural and microstructural characteristics, including cell parameters and crystallite size. Uneven aggregation of nanoparticles in the nano-scale with distinctive porosity can be seen in the TEM micrograph. Kubelka-Munk model imitative diffuse reflectance spectra and an optical band gap of 5.67 eV for the Y_3.97Al₂O₉:0.03Tb³⁺ nanophosphor revealed high optical quality in the samples, which were thought to be non-conducting. The emission (PL) and excitation (PLE) spectra as well as lifetime measurements have been used to determine the luminescence characteristics of the synthesized nanophosphors. The emission spectra show two color i.e. blue color due to ⁵D₃ → ⁷F _J (J = 4 and 5) transitions and green color due to ⁵D₄ → ⁷F _J (J = 3, 4, 5 and 6) transitions. The most dominant transition (⁵D₄ → ⁷F₅) at 548 nm was responsible for the greenish color in focused nanocrystalline samples. Calculated colorimetric characteristics such as CIE, and CCT along with color purity of the synthesized nanocrystalline materials make them the best candidate for the solid-state lighting (SSL).

Gadolinium-based Sm3+ activated GdSr2AlO5 nanophosphor: synthesis, crystallographic and opto-electronic analysis for warm wLEDs

A material's luminosity characteristics, which in turn dictate its applicability, are critically influenced by its structure. Therefore, it is essential for design and fabrication of optical nanocrystalline materials to comprehend the relationship between structural and luminescence properties. The gel-combustion approach was used to produce a sequence of orange-red light emanating GdSr₂AlO₅:Sm³⁺ (GSA:Sm³⁺) nanophosphors which are used for warm white-light-emitting diodes (w-LEDs). Comprehensive investigation of the structural and optical characteristics of GdSr₂AlO₅:Sm³⁺ nanophosphors has been done in a detailed manner. The synthesized powdered nanophosphors are crystallized in a tetragonal phase with I4/mcm (140) space group, affirmed through Rietveld refining method. The nano size with an aggregated, spherical form of the particles in the powdered nanocrystalline material was revealed by TEM analysis. These orange-red emitting phosphors Gd_1-x Sr₂AlO₅:xSm³⁺ (x = 1-7 mol%) were shown to possess photoluminosity (PL) properties that demonstrated the presence of most intense emission peaks at 603 nm that were caused by ⁴G_5/2 → ⁶H_7/2 transitions of the Sm³⁺ ion under 273 nm excitation. Considering its long decay lifespan and PL emission, it can be concluded that the GdSr₂AlO₅:Sm³⁺ phosphor is a potential single element for the fabrication of warm white light-emitting devices.