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Abstract: Recently, rare-earth activated phosphors have gained new and exciting applications in various fields, like display and illumination, phototherapy, plant growth, etc. The phosphorconverted white light emitting diode is prime in the art of solid-state lighting owing to its numerous merits, including desired spectral distribution, excellent chemical and thermal stability, high operational lifetime, reliability, and color quality of w-LEDs for lighting. The enhancement of the color gamut of backlight w-LEDs still needs to be addressed, which requires the design of high-efficient downshifting converter phosphors featuring thermally stable luminescence. The class of materials under suitable activation exhibit applications in a particular field. The emission in the UV region (312-315nm) is widely used for phototherapy lamps. Phototherapy has proven to be an excellent therapeutic option for the treatment of various types of skin diseases. Moreover, the emission corresponds to 600-750nm for plant cultivation. The present review article describes various rare-earth activated phosphors and their impact on human and plant physiology.

The series of Mn2+ single doped fluoride-based K3Ca2(SO4)3F phosphor was prepared by the conventional high temperature solid-state reaction method. The formation of phase purity and morphology was ...

Near-UV (NUV)-excitable blue-light-emitting Eu2+ ions-doped Ca-chabazite Ca1.9Al3.8Si8.2O24 phosphor was synthesized by facile urea-assisted combustion synthesis method. Prepared materials were characterized by X-ray diffraction (XRD) study, scanning Electron Microscopy (SEM), and photoluminescence (PL) spectroscopy. The Eu2+-doped Ca1.9Al3.8Si8.2O24 calcium aluminosilicate phosphor exhibited intense and broad emission in the blue region. CIE chromaticity coordinates were plotted and obtained values were compared with standard NTSC coordinates. Electron vibration interaction (EVI) parameters such as Huang Rhy’s factor (S) and effective phonon energy (ħω) were calculated to determine the strength of electron–phonon coupling. The prepared mineral-based blue-emitting Near-UV-excitable phosphor may prove to be a potential candidate as a blue component for the white light emitting diode (wLED).

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...

We report here, the Ca9La(PO4)5(SiO4)F2:1 mol%Eu3+ phosphor via doping of chloride, molybdate, vanadate, sulfate, and tungstate ions that were synthesized by high-temperature solid-state reaction method. The phase formation was confirmed by X-ray diffraction (XRD) measurements. Morphological studies were performed using scanning electron microscopy. Photoluminescence and thermoluminescence properties of the synthesized phosphors were systematically studied. The PL excitation spectra of host material show peaks at 395 nm and 466 nm corresponding to 7F0 → 5L6 and 7F0 → 5D2 transitions of Eu3+, respectively. Further photoluminescence properties also studied after doping of molybdate, vanadate, sulfate, and tungstate ions in host material. When excited at 395 nm and 466 nm, PL emission spectra show emission band at around 595 nm and 616 nm, which attributes to 5D0 → 7F1 and 5D0 → 7F2 transitions, respectively. Further TL glow curves of all the synthesized phosphors were studied when exposed to γ-rays.

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.

Because of the importance of inorganic phosphates in the solid-state lighting industry, KZnPO4doped with some transition metal dopant ions like Cu+and Ag+ions were prepared by low-cost co-precipitation method at room temperature followed by annealing at a high temperature around 6500C. The prepared phosphors were characterized by X-ray diffraction. In the case of a Photoluminescence study for KZnPO4doped with Cu+, the emission was observed at 425 nm, which corresponds to the emission of Cu+ion. In the case of Ag+doped KZnPO4, weak emission was observed at 420 nm, which is assigned to the emission of Ag+ions. CIE chromaticity coordinate of KZnPO4doped with Cu+and Ag+ions phosphor was also evaluated via using OSRAM SYLVANIA color calculator and colour purity of concentration was nearly 95% of Cu+and Ag+ions. The obtained outcomes revealed that the prepared phosphor shows potential application in the field of solid-state lighting.

The trivalent Eu3+ activated KMg4(PO4)3 phosphor has been successfully prepared via solid state diffusion technique. The phase formation and structural morphological studies carried out by XRD pattern and SEM analysis. The photoluminescence excitation spectra centred at 395 nm attributed to 7F0→5L6 energy transition levels. PL emission spectra centred at 593 nm and 613 nm corresponds to 5D0→7FJ( J=1,2) transitions of Eu3+ in the host respectively. The experimental results showed that Eu3+ singly doped KMg4(PO4)3 phosphor under UV excitation gives intense red emissions. The critical Eu3+ quenching concentration (QC) was determined to be 1.0 mol% along with excellent CIE coordinates of (0.6326, 0.3670). All the above results exhibits, the prepared phosphor is promising material as UV excitable red emitting phosphor for w-LED.

The phosphor converted w-LEDs gaincrucial attention in solid state lighting (SSL) for generation of illumination owing to their numerous meritorious advantages such as superior life time, excellent efficiency, compactness, reliability and power saving consumption as well as environmental friendly. The quality of w-LEDs in lighting and display is influence by host phosphorand the choice of activator. So greatlyattemptwere dedicated to developed inventiveuni-nucleiluminescent phosphor materials compose of chromatic stability, optimum CRI and low correlated color temperature. This review elaborate theintroduction ofEu3+rare earth activated red emitting phosphor assigned to 5D0→7FJ (J= 1,2,3,4) energy levelsand its fundamental merit for w-LEDs. This article represent the analyseofcombination of different types of Eu3+ activated luminescent materials by traditional and novel methods and its impact on photoluminescence for SSL.

The present study reported synthesis of Dy3+activated CaAl2Si4O12 phosphor via combustion techniques. The formation of crystal structure and surface morphology was analysed by X-ray diffraction pattern and scanning electron microscopy. The photoluminescence spectrum reveals, the prepared phosphor material exhibits an excellent emission at 422 nm, with two peaks around 479 nm (blue region) and 575 nm (yellow region) monitor at excitation wavelength of near UV 369 nm. In addition, CIE color chromaticity confirms the emission locate at the blue light region, revealed suitability of prepared phosphor in UV excitable blue emission for white light emitting diode. The Thermoluminescence characterization of prepared phosphor irradiated with a 60 Co γ- ray source at dose rate of 7.2 kGy/hr was further carried out using a Nucleonix TL 1009I TL reader. The tapping parameter such as activation energy (E) and frequency factor (s) was calculated using Ilich's method.

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.

In the present paper, we have successfully synthesized Eu2+ activated K3Ca2(SO4)3F phosphor by two-step solid-state reaction method at high temperature (800 °C). Pure crystalline formation, morphological behavior, and their vibration bonds of synthesized Eu2+ activated K3Ca2(SO4)3F phosphor were verified by the X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier transform Infrared Spectrum (FT-IR). The photoluminescence (PL) spectrum and CIE coordinate with color purity also characterized. In PL emission spectra clearly represented that broad excitation band from 250 nm to 400 nm ranged. The center of this PL excitation spectra observe at 326 nm, but some parts of these spectra lies to 350 nm–400 nm. This excitation wavelength is very useful for the generation of white light because it may be used as near UV light. PL emission represents broad emission spectra from 400 nm to 550 nm centred at 440 nm. Most part of these PL emission spectra lies in the blue region of the spectrum. PL spectra arise from the transitions between the 5d and 4f orbital’s transition of Eu2+ ions. EVI parameters such as Stokes Shift (ΔEs), the Huang-Rhys factor (S),effective phonon energy (ħω) and the Zero-phonon line (ZPL) are calculated. In our present work, we are calculated that the value of Huang–Rhys factor constant (S) is 3.74 that means coupling is intermediately strong. CIE chromaticity coordinate of K3Ca2(SO4)3F:xmol%Eu2+[x = 0.5, 2.0, 3.0, 5.0, 7.0, 10mol%] phosphor were also calculated by using OSRAM SYLVANIA color calculator 1931. By using these CIE chromaticity coordinate was calculated the value of color purity for each concentration of Eu2+ ions. After seeing all results of synthesized phosphor material we are concluded that it may be a better option used as commercial phosphor for obtaining white light. So it may be a promising candidate for NUV WLEDs.

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.