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A trivalent Dy3+ -activated K3 Ca2 (SO4 )3 F fluoride-based phosphor was synthesized using a solid-state reaction method and characterized for its thermoluminescence (TL) application. The crystal structure and surface morphology of the as-synthesized material was analyzed using X-ray diffraction and scanning electron microscopy. A series of the K3 Ca2 (SO4 )3 F:Dy3+ phosphor was irradiated using γ-rays from a 60 Co source and TL glow curves were recorded using a Nucleonix 1009I TL reader. The glow curve of the prepared phosphor showed a prominent single peak at 278°C. TL characteristics were maximum intensity at 1 mol% of Dy3+ ion with a single TL glow peak. The TL glow curve revealed linearity with increase in exposure dose range from 0.1 kGy to 3.0 kGy. Theoretical analysis of the TL glow curve of the γ-ray-irradiated sample was carried out using a computerized glow curve deconvolution method and trapping parameters such as activation energy and frequency factor were calculated using the initial rise method and Ilich's method. The synthesized Dy3+ -doped K3 Ca2 (SO4 )3 phosphor revealed excellent TL properties and was found to be a potential candidate for dosimetric applications.

Fluorapatite Ca9La(PO4)5(SiO4)F2: Eu with variable molar concentrations of Eu3+ (0.05–1.0 mol%) were synthesised by the solid-state reaction method and their photoluminescence (PL), thermoluminesce...

The fluoroapatite Ca9La(PO4)5(SiO4)FCl:1 mol% Eu3+ phosphor was synthesized by conventional solid state reaction. In the present work keeping concentration of F1Cl1 constant and (PO4)3− of the material was replace by (MoO4)3−. The phase purity and surface morphology was evaluated through X-ray diffraction and scanning electron microscope technique. The emission and excitation spectra were investigated using photoluminescence spectroscopy. The excitation and emission spectra indicate that prepared phosphor effectively excited by 278 nm, exhibits emission peak at 595 nm and 616 nm corresponds to yellow and red colour attributes to 5D0→7F1 and 5D0→7F2 transitions respectively. The above result reveals prepared phosphor is excellent red phosphor in white light emitting diode application.

Perovskites based LEDs (PeLEDs) have emerged as solid-state devices with sharp linewidths and economical as compared to the organic light-emitting diodes. Several factors contribute to limit the performances of the PeLED devices and hence this review systematically accounts for the main issues that PeLEDs face in their commercialization in light industries. Modification of the cation size via A-site substitution and substitutions at B- and X-sites have been dealt in detail and fine-tuning of electronic structure and optoelectronic properties due to the change in the crystal environment has also been emphasized. The dynamics of the photo-excited state, charge transport, electronic structure, non-radiative recombination, pin-hole formation, exciton confinement have been discussed in detail to improve the PeLED performance. The methods for post-synthesis transformation and low-cost solution-based fabrication have been discussed. We also address the novel studies on quasi-2D perovskites for high spectral stability and other passivating systems. The suggestions have been made for next-generation PeLEDs based on the search for novel emitter material, optimization of charge injection, and light extraction efficiencies. The efficiencies of PeLEDs can be boosted by employing various light-outcoupling techniques have also been demonstrated.

Inorganic phosphors based on RbBaScSi3O9 (RBS), a chemically and thermally stable host doped with Ce3+; Eu2+ and codoped with Ce3+/Eu2+ and Eu2+/Dy3+ ions have been developed by an ‘amorphous based metal complex method’ using a water soluble silicon compound. The phase purity of the phosphors has been verified by X-ray powder diffraction technique. RBS:Ce3+(4%) phosphor exhibits a broad excitation spectrum in UV spectral region and a broad emission band centred at ∼439 nm with a full-width at half-maximum of ∼85 nm under the UV excitation. RBS:Eu2+ phosphor showed intense cyan-green emission which has been found to increase by three times in Ce3+/Eu2+ co-doped phosphors owing to the energy transfer from Ce3+ to Eu2+ in RBS:Ce3+, Eu2+ phosphor. Moreover, by co-doping RBS with Eu2+ and Dy3+ ions, the cyan-green emission of Eu2+ has been found to enhance considerably; about 6.9 times higher as compared to the emission intensity of RBS:Eu2+ phosphor. This increase is attributed to the generation of large number of traps similar to the pre-existing traps as a result of the incorporation of Dy3+ ion in RBS host and the enhancement in PL has also been substantiated from the enhanced thermoluminescence intensity of RBS:Eu2+, Dy3+ phosphor with respect to RBS:Eu2+ phosphor. Although the afterglow duration of RBS:Eu2+ and RBS:Eu2+, Dy3+ phosphors are in the similar range, but the afterglow intensity of half maxima was found to be 1.63 times higher in RBS:Eu2+,Dy3+ as compared to RBS:Eu2+ which owes to the enhanced photoluminescence intensity of the former as compared to the latter. The short but intense afterglow of RBS:Eu2+,Dy3+ phosphor indicates its potential for making glow bullet for defense application. Furthermore, when compared with, the photoluminescence (PL) emission intensity of near UV- excitable RBS:Eu2+, Dy3+ phosphor has been found to be ∼2 times higher than the green emitting commercial phosphor from Intermix reflecting the potential of this phosphor for the fabrication of phosphor-converted LED.

La1-xPO4:xTb (x = 0.01 ≤ x ≤ 0.11) phosphors were synthesized using conventional co-precipitation method. The powder X-ray diffraction confirmed the pure phase formation of LaPO4 host material. Upon ultra-violet (UV) excitation and vacuum ultra-violet (VUV), the phosphor showed a dominant green emission band centered at 544 and 545 nm, respectively due to the 5D4→7F5 transition of Tb3+. The concentration quenching phenomena occurred when Tb3+ concentration was beyond 0.09 mol and this quenching mechanism could be explained by the dipole-dipole interaction. The optimal concentration was found to be 0.09 mol of Tb3+ ion. The CIE chromaticity coordinates of the optimized (La0.91PO4:0.09Tb) phosphor was determined to be (0.265, 0.567). All the analyzed results confirms that the La1-xPO4:xTb (x = 0.01 ≤ x ≤ 0.11) phosphors can find possible applications as promising green-emitting phosphor in near UV and VUV used in plasma display panels.

Dy3+ doped SrAl12O19 phosphors, capable of radiating white light, were successfully synthesized via combustion method. Phase identification, morphological observations and elemental examination were done by employing X-ray diffraction, Field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The peaks in the X-ray diffraction patterns are found to be indexed well with the hexagonal phase (JCPDS card number 80-1195). Under 350 nm of excitation wavelength, the PL emission bands were peaking at 478 nm and 573 nm, which can be ascribed to the intra-4f transition of Dy3+. The emission data were analyzed for determining the CIE chromaticity coordinates and the correlated color temperature (CCT). A cool white light with chromaticity coordinates x = 0.3098 and y = 0.3538 and correlated color temperature of 6542 K was achieved for 3 mol% at 350 nm excitation. These results indicate that SrAl12O19:Dy3+ have practical applications in UV-pumped white light emitting diodes.