Synthesis of Sr2Si5N8:Ce3+ phosphors for white LEDs via an efficient chemical vapor deposition [corrected]

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.

Multiemission of Ce3+ from a Single Crystallographic Site Induced by Disordering of Ions

White-light emission with a single activator is an attractive function of phosphors. In this work, we investigated the photoluminescence properties of Ca5.7Y1.3Si7O16.7N3.3, which is a compound denoted as Ca4+xY3-xSi7O15+xN5-x discovered by our group, with Ce-activation using optical measurements and density functional theory (DFT) calculation. Samples showed a tunable emission from purple to white under ultraviolet (UV) light. In this compound, Ca and Y as well as anions are distributed disorderly, and Ca/Y ions occupy two crystallographically distinct sites; those sites are possible sites for Ce substitution. DFT calculation and structural refinement revealed that the tunable emission was generated by Ce at the crystallographically equivalent site but with distinct local structures caused by the disordering of cations and anions. As far as we know, this is the first report about a white-light-emitting phosphor with only Ce activation.

Luminescent properties of Eu3+-activated Gd2ZnTiO6 double perovskite red-emitting phosphors for white light-emitting diodes and field emission displays

We synthesized a series of double perovskite Eu3+-activated Gd2ZnTiO6 red-emitting phosphors by a solid-state reaction route and analyzed their morphology, crystallinity, luminescent properties, and thermal stability. Under 270 nm of excitation, the prominent emission peak of the phosphors was found to be located in the red region with the central wavelength of 613 nm corresponding to the intra-4f transition of Eu3+ ions from the 5D0 to 7F2 level. The optimum concentration of the activator was determined to be 7 mol%. The studied phosphors also exhibited good thermal stability with the activation energy of 0.233 eV. The white color emitted from the ultraviolet (UV) light-emitting diode device which was coated by commercial blue-/green-emitting phosphors and Gd1.86ZnTiO6:0.14Eu3+ phosphors exhibited a high color rendering index of 82.9. Furthermore, the cathodoluminescence performance of the resultant phosphors was also investigated in detail. These characteristics of Gd2-2x ZnTiO6:2xEu3+ phosphors make them potential candidates for UV-based white light-emitting diodes and field emission displays.

Eu3+-activated La2MoO6-La2WO6 red-emitting phosphors with ultrabroad excitation band for white light-emitting diodes

A series of novel Eu³⁺-activated La₂MoO₆-La₂WO₆ red-emitting phosphors have been successfully prepared by a citrate-assisted sol-gel process. Both photoluminescence excitation and emission spectra suggest that the resultant products have the strong ultrabroad absorption band ranging from 220 to 450 nm. Under the excitation of 379 nm, the characteristic emissions of Eu³⁺ ions corresponding to the ⁵D₀ → ⁷F_J transitions are observed in the doped samples. The optimal doping concentration for Eu³⁺ ions is found to be 12 mol% and the quenching mechanism is attributed to the dipole-dipole interaction. A theoretical calculation based on the Judd-Ofelt theory is carried out to explore the local structure environment around the Eu³⁺ ions. The studied samples exhibit a typical thermal quenching effect with a T_0.5 value of 338 K and the activation energy is determined to be 0.427 eV. A near-ultraviolet (NUV)-based white light-emitting diode (LED) is packaged by integrating a mixture of resultant phosphors, commercial blue-emitting and green-emitting phosphors into an NUV LED chip. The fabricated LED device emits glaring white light with high color rendering index (84.6) and proper correlated color temperature (6492 K). These results demonstrate that the Eu³⁺-activated La₂MoO₆-La₂WO₆ compounds are a promising candidate for indoor lighting as red-emitting phosphors.