CIE Color Coordinates Research Articles

Concentration dependent Dy3+- doped lithium fluoro borotellurophosphate glasses’ structural and optical investigations for white light emission under UV excitation for solid-state lighting applications

Concentration dependent Dy3+ - doped lithium fluoro borotellurophosphate glasses were prepared by conventional melt quenching technique by varying the dopant concentration (0.1, 0.25, 0.5, 1.0 & 1.5 wt %). The structural and compositional analyses have been carried out through XRD, FTIR, SEM and EDAX respectively. The optical studies were made to analysis the optical behavior of the Dy3+ ions in the synthesized glasses through absorption and emission spectra. The nephelauxetic ratio and bonding parameter were calculated from the absorption spectra. The oscillator strength fexp and fcal along with σrms were evaluated and reported. The JO intensity parameters (Ω2, Ω4 and Ω6) have been calculated and trends reported. The photoluminescence spectra were recorded under 384 nm excitation. The radiative properties like emission band position (λp), effective bandwidth (Δλeff), radiative transition probability (A), stimulated emission cross-section (σpE), calculated and experimental branching ratios (βR) for the Dy3+-doped lithium fluoro borotellurophosphate glasses were calculated using JO intensity parameters and emission data. The CIE color coordinates (x,y) and Y/B ratio values were calculated from the photoluminescence spectra. The color correlated temperature (CCT) were determined from the (x,y) values and possibility for white light emissions from the synthesized glasses were analyzed under UV excitation. The decay analysis shows the non-exponential behavior of the present glasses.

The Effect of Ni2+ Ions Substitution on Structural, Morphological, and Optical Properties in CoCr2O4 Matrix as Pigments in Ceramic Glazes.

The structural, morphological, and optical properties of Ni2+ ions substitution in CoCr2O4 matrix as ceramic pigments were investigated. The thermal decomposition of the dried gel was performed aiming to understand the mass changes during annealing. The X-ray diffraction (XRD) studies reveal a spinel-type Face-Centered Cubic structure and a secondary Cr2O3 phase when x ≤ 0.75 and a Body-Centered Tetragonal structure when x = 1. Fourier Transform Infrared Spectroscopy (FT-IR) indicated two strong absorption bands corresponding to the metal-oxygen stretching from tetrahedral and octahedral sites, characteristic of spinel structure. Ultraviolet-Visible (UV-Vis) spectra exhibited the electronic transitions of the Cr2+ Cr3+ and Ni2+ ions. From the UV-Vis data, the CIE color coordinates, (x, y) of the pigments were evaluated. The morphology was examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) showing the agglomeration behavior of the particles. The stability, coloring properties and potential ceramic applications of studied pigments were tested by their incorporation in matte and glossy tile glazes followed by the application of obtained glazes on ceramic tiles. This study highlights the change in pigment color (from turquoise to a yellowish green) with Ni2+ ions substitution in the CoCr2O4 spinel matrix.

Blue luminescent properties of Ce3+/Gd3+ co-doped NaBaBO3 phosphors

Ce3+ and Gd3+ co-doped NaBaBO3 blue luminescent materials were synthesized by the solid-state reaction. X-ray diffraction, X-ray photoelectron spectrometer, and fluorescence spectrometer were used to analyze the crystal structure, the surface morphology, and the luminous properties. Ce3+/Gd3+ co-doped NaBaBO3 phosphors can absorb near-ultraviolet light and emit bright blue light centered at 430 nm, which originates from the 5d-4f transition of Ce3+ ion. When the doping concentration of Ce3+ and Gd3+ was 1 % and 3 % respectively, Ce3+/Gd3+doped NaBaBO3 had the strongest luminous intensity with a short decay time of about 23 ns. The addition of Gd3+ increases the luminescence intensity of Ce3+ doped NaBaBO3. The CIE color coordinates are (0.1564, 0.0909). Ce3+/Gd3+ co-doped NaBaBO3 powders are promising materials for WLEDs and scintillators.

Derivatives of Imidazole and Carbazole as Bifunctional Materials for Organic Light-Emitting Diodes.

New derivatives of carbazole and diphenyl imidazole for potential multiple applications were synthesized and investigated. Their properties were studied by thermal, optical, photophysical, electrochemical, and photoelectrical measurements. The compounds exhibited relatively narrow blue light-emission bands, which is favorable for deep-blue electroluminescent devices. The synthesized derivatives of imidazole and carbazole were tested as fluorescent emitters for OLEDs. The device showed deep-blue emissions with CIE color coordinates of (0.16, 0.08) and maximum quantum efficiency of 1.1%. The compounds demonstrated high triplet energy values above 3.0 eV and hole drift mobility exceeding 10-4 cm2/V·s at high electric fields. One of the compounds having two diphenyl imidazole moieties and tert-butyl-substituted carbazolyl groups showed bipolar charge transport with electron drift mobility reaching 10-4 cm2/V·s at electric field of 8 × 105 V/cm. The synthesized compounds were investigated as hosts for green, red and sky-blue phosphorescent OLEDs. The green-, red- and sky-blue-emitting devices demonstrated maximum quantum efficiencies of 8.3%, 6.4% and 7.6%, respectively.

Effect of dopant (Li+, Mg2+ and Bi3+) on the photoluminescence emission intensity of Eu3+ doped CaAl2O4 phosphor: Application to white LEDs

In this work, we have investigated the photoluminescence (PL) emission properties of Eu3+ doped CaAl2O4 in the presence of singly, doubly and triply ionized dopant ions i.e., Li+, Mg2+ and Bi3+ ions. The phosphor samples were synthesized by the high-temperature solid-state reaction process at 1473 K. The crystalline phase, crystallinity and surface morphology of Li+, Mg2+ and Bi3+ ions doped 0.01Eu3+:CaAl2O4 phosphor were examined and confirmed by X-Ray diffraction (XRD) and scanning electron microscope (SEM) measurements. The different vibrational groups and their corresponding vibrational frequencies were measured by Fourier transform infrared (FTIR) technique. The 0.01Eu3+:CaAl2O4 phosphor emits intense red emission at 616 nm on excitations with 393 nm (Eu3+ line) and by the charge transfer band (Eu3+-O2-) at 262 nm. The overall PL emission intensity of 0.01Eu3+:CaAl2O4 phosphor on excitation with 393 nm is found to increase almost 2.8 times in the presence of Li+ than other dopants. The emission intensity are increased in case of Li+ and Mg2+ doping due to crystallinity, charge compensation and the asymmetry created around the Eu3+ ions in the phosphors matrix. However, in case of Bi3+ ion, the emission intensity decreases on 393 nm excitation. In the presence of Bi3+ ion the intense red emission is observed due to energy transfer from Bi3+ (3P1→1S0) to Eu3+ ion on λexc = 294 nm. The lifetime study were carried in each case which are in accordance with the PL emission behaviour of Li+, Mg2+ and Bi3+ ions doped 0.01Eu3+:CaAl2O4 phosphor. The CIE color coordinates, correlated color temperature (CCT) and color purity have been calculated, which shows highly pure red color in the warm light region. The 0.01Eu3+:0.10Li+:CaAl2O4 phosphor may be used in displays devices, photonic devices, solid state lighting as red light emitting source.

Frontier Molecular Orbitals Regulation Enables Efficient and Ultraviolet to Deep‐Blue Narrowband Emission

AbstractModulating the emission wavelength in the range of ultraviolet to deep‐blue with high color purity remains elusive. Herein, a versatile strategy is proposed from the perspective of rationally regulating nonbonding/π‐bonding character of frontier molecular orbitals to finely modulate emission colors while retaining superior color purity. By modifying the fused modes of indolo[3,2,1‐jk]carbazole (ICz) units, the proof‐of‐the‐concept emitters emphasize adjustable hybridization of nonbonding and π‐bonding characteristics, achieving a wide‐range color tuning range from ultraviolet (380 nm) to deep‐blue (428 nm) and small full‐width at half‐maximum (FWHM) of 8–33 nm (63–222 meV). Organic light‐emitting diodes based on the new emitter exhibit electroluminescence emission at 430 nm, a small FWHM of 44 nm (253 meV), maximum external quantum efficiency of 10.9%, and CIE color coordinates of (0.16, 0.05). The CIE coordinates are close to the National Television System Committee (NTSC) standard blue of (0.15, 0.06).

A novel efficient red-emitting K7SrY2B15O30: Eu3+ phosphor with non-concentration quenching and robust thermal stability for white LEDs

Inhibiting energy migration between Eu3+ ions in a fixed host to get higher doping concentration is a permanent topic. Herein, a novel non-concentration quenching red-emitting K7SrY2-2xB15O30: xEu3+ (0.1 ≤ x ≤ 1.0) phosphor was synthesized via high-temperature sintering method. XRD measurement, Rietveld refinement results, and radius percentage deviation calculation demonstrated the phase purity and the occupation preference of Eu3+ ions. With continuously increasing doping Eu3+ ions, the absence of concentration quenching could be explained by long distance between two Eu3+ (7.012 Å) and the K7SrEu2B15O30 could exhibit striking photoluminescence performance with the highest emission wavelength centered at 617 nm. Meanwhile, under the radiation of 393 nm, the high internal quantum efficiency ( ∼ 78.71 %), excellent color purity ( ∼ 88.32 %) and robust thermal stability whose emission intensity at 140 °C could still reach ∼ 97.31 % could guarantee its potential application. When coating BaMgAl10O17: Eu2+, (Ba, Sr)2SiO4: Eu2+, and K7SrEu2B15O30 on a near-ultraviolet chip, the bright white light with a low correlated color temperature of 4211 K and CIE color coordinates of (0.3675, 0.3556) could be obtained. Taking the analytic results above, the non-concentration quenching K7SrY2B15O30: Eu3+ compound has great potential to act as a candidate for red-emitting phosphors in solid-state lighting field.

New Dy3+-activated KCa2Nb3O10 yellow-emitting phosphors for w-LEDs application: Preparation and optical properties

A novel single-phase KCa 2 Nb 3 O 10 :Dy 3+ yellow-emitting phosphor can be efficiently excited under 388 nm irradiation. • KCa 2 Nb 3 O 10 :Dy 3+ phosphors have been firstly synthesized using the molten-salt method. • The KCa 2 Nb 3 O 10 :Dy 3+ product shows excellent thermal stability with high temperature quenching temperature. • The KCa 2 Nb 3 O 10 :Dy 3+ product shows rich UV excitation band and yellow light emission. • The CIE color coordinates of prepared KCa 2 Nb 3 O 10 :Dy 3+ phosphors change slightly. A series of Dy 3+ doped KCa 2 Nb 3 O 10 niobate phosphors that generated yellow emission was prepared using the molten-salt method. The crystal structure, X-ray diffraction (XRD), optimal concentration, photoluminescence excitation/emission (PLE/PL), and luminescent stability of the prepared phosphors were exhaustively studied. The KCa 2 Nb 3 O 10 lattice has a perovskite-like structure, which possesses the Cmcm (No.63) space group. The KCa 2 Nb 3 O 10 :Dy 3+ phosphors can be efficiently excited by n -ultraviolet ( n -UV) excitation of 388 nm. Besides, KCa 2 Nb 3 O 10 :Dy 3+ phosphors can emit three dominant peaks centered at 486, 577, and 662 nm, which are ascribed to the 6 H J /2 ( J = 15/2, 13/2, and 11/2) transitions, respectively. The optimum doping concentrations of Dy 3+ ions in the KCa 2 Nb 3 O 10 host are determined to be 0.02 mol. The thermal-quenching temperature ( T 0.5 ) for the KCa 2 Nb 3 O 10 :0.20Dy 3+ sample is estimated to be above 500 K, and the calculated activation energy ( E a ) is 0.29 eV. Furthermore, the Commission International de I'Eclairage (CIE) color coordinates of prepared KCa 2 Nb 3 O 10 :Dy 3+ phosphors change slightly. KCa 2 Nb 3 O 10 :Dy 3+ phosphors possess good color purity, color stability, and low correlated color temperature (CCT). All results indicate that the KCa 2 Nb 3 O 10 :Dy 3+ phosphors are suitable for white light-emitting diodes (w-LEDs) applications.

Effect of U on the photoluminescence of Pr and structural properties of U/Pr doped and co-doped Li2O–ZnO–SrO borophosphate glass

U/Pr doped and co-doped Li2O–ZnO–SrO borophosphate glasses were prepared using the melt quenching method. XRD, SEM-EDX, and FTIR investigations were carried out to ascertain the structural properties, morphological features and homogeneity of elemental distribution in the synthesised glass phosphors. Differential thermal analysis was used to examine the thermo-physical properties. It was observed that uranium doping improved the thermal stability and rigidity of the synthesised glass host. Intense photoluminescence (PL) emissions were observed both from uranium and praseodymium in the U/Pr doped glass. Uranium showed a broad emission spectrum with peak a maximum at 526 nm and resembles the typical emission pattern of hexavalent uranyl species (UO22+) in the amorphous environment. UO22+ emission increased linearly until the onset of concentration quenching at 1.0 mol%. Similarly, praseodymium doped glasses exhibited intense red emission from overlapped 3P0→ 3H6 and 1D2 →3H4 transitions, and centred at around 609 nm. At 0.2 mol%, the Pr emission intensity was highest, concentration quenching was prevalent beyond it. The emission decay of both uranium and praseodymium followed the bi-exponential decay model and the lifetime values decreased with increasing the dopant concentration in singly doped as well as co-doped samples. The Inokuti-Hirayama model was employed for the fitting of decay profiles to explicate the nature of non-radiative interaction of excited states. The donor-acceptor coupling parameters (Cda) were determined for U–U, Pr–Pr, and U–Pr interaction. Appreciable U–Pr energy transfer via dipole-dipole interaction was observed with Cda = 4.79 × 10−40 cm6s−1. Emission of both Pr and U get suppressed in the co-doped glass samples possibly due to the concomitant U–Pr redox interactions. The CIE color coordinates and color purity suggested that U/Pr doped Li2O–ZnO–SrO borophosphate glass can be used for solid-state lighting applications.

Influence of co-doping alkali metal ions Li+/Na+/K+ on the luminescence enhancement properties of the blue emission from Pb2+/Bi3+ activated di-barium calcium di-zinc hexa-silicate based phosphors for solid state light applications

The non rare earth element Pb2+/Bi3+ activated and alkali metal Li+/Na+/K+ ions codoped with the silicate based Ba2CaZn2Si6O17 (hereafter mentioned as BCZSO) blue-emitting phosphors were prepared through a simple solid state reaction route and characterized. The phase identification of the as prepared samples was done by taking the powder X-ray diffraction (PXRD). The Rietveld refinement of the as prepared phosphor was analyzed. The morphological analysis was performed using the scanning electron microscope (SEM). The photoluminescence (PL) and PL excitation (PLE) properties of the phosphors were investigated. Exciting the BC1-xZSO:xPb2+ phosphor with 295 nm light yielded a wide blue emission centered at 438 nm. Also, when the BC1-xZSO:xBi3+ phosphor was excited with 317 nm, a bright blue emission at 465 nm was observed. The Stokes shift values of these phosphors were calculated to be 11,067, and 10,040 cm−1 in the same order. The optimum concentrations for the Pb2+, and the Bi3+ ions in the BCZSO host were found to be 3 and 7 mol % respectively. The critical distance (Rc) values were calculated to be 29.32 Å and 23.05 Å for the Pb2+ and the Bi3+ activated BCZSO phosphors respectively. When the alkali metal ions were co-doped in the blue emitting phosphors, a PL enhancement was observed. The decay lifetime was calculated for the BCZSO: M (M:Pb2+/Bi3+) phosphors, and found to decline with increasing concentration of the activators. The CIE color coordinates, and the quantum efficiency of these silicate phosphors were calculated. These values for the BC1-xZSO:xPb2+ phosphor were closer to the commercial blue BaMgAl10O17:Eu2+ (BAM) phosphor. In addition, the temperature dependent photoluminescence (TDPL) spectra were recorded to examine the thermal stability of this phosphor. These results suggest that the BCZSO:M (M:Pb2+/Bi3+) and the BC1-x-yZSO:xPb2+/Bi3+, yLi+/Na+/K+, blue emitting phosphors can serve as promising candidates for white light emitting diodes (WLEDs).

Synthesis and in-depth investigation of the photophysical and electrochemical properties of novel pyrazole cored D-A-D molecules

The synthesis of a novel pyrazole-cored push-pull system (Donor-Acceptor-Donor/D-A-D) in which thiophene serves as the donor and N-substituted pyrazole ring serves as the acceptor moieties is reported. The photophysical and electrochemical properties of the synthesised compounds were investigated using UV–Visible spectroscopy, photoluminescence spectroscopy, and cyclic voltammetry (CV). The photophysical results indicate that all four compounds have unique absorption and emission behaviour in the solid-state compared with the solution (in CHCl3). The optical band gap was calculated from the absorption curve and ranged from 2.75 eV to 3.81 eV. According to the CIE colour coordinates, each compound can emit different colour ranges. The estimated electrochemical results (HOMO and LUMO energy values) by CV and the possibility of adaptable tuning of these results demonstrate that the target compounds can be used as a fresh emissive candidate for organic optoelectronics applications. The significance of push-pull architecture and the solid-state emission properties of the targeted compounds were also highlighted in this work.

Anti-solvent polarity engineering for structure, morphology and composition control of cesium copper (I) halide with efficient, stable and adjustable photoluminescence

In this work, cesium copper (I) halide micro-crystals (MCs) were demonstrated to experience structure, morphology and composition evolutions by tuning the polarity of the anti-solvent. It was fond that, when anti-solvents with the polarity higher than 4.3+ were used, rod-like phase-pure CsCu2I3 MCs, rather than Cs3Cu2I5 MCs, preferred to be formed. However, when the anti-solvents with polarity came to lower than 4.3-, particle-state Cs3Cu2I5 MCs would be produced. With the structural evolution from CsCu2I3 to Cs3Cu2I5, the photoluminescence emission changed from yellow to blue, with high photoluminescence quantum yields (PLQYs) of 15.3% and 89.5%, respectively. Amazingly, by a fine tuning of the polarity in the range from 4.3+ to 4.3-, the mixing ratio of CsCu2I3 and Cs3Cu2I5 MCs can be adjusted directly, with tunable Commission Internationale de L′Eclairage (CIE) color coordinates from cold white to white and warm white, by changing the relative volume of the anti-solvent. Note that, the dependences of the production on the polarity of the anti-solvent showed rather wide precursor’s molar ratio and concentration processing windows. At last, the as-prepared white-light mixture was placed onto a UV LED chip to fabricate a white-light emitting diode (WLED). The device showed a high color rendering index of 87.3, a CIE color coordinate of (0.32, 0.33), and a long life time of more than 100 h. The discovered relationships between the anti-solvent polarity and structural evolution of the cesium copper (I) halide MCs enriched our understanding about copper-containing perovskite-like halides. The method to fabricated white-light phosphor in one step greatly simplified the technological process and reduced the production cost. And, the perfect stability of the WLED demonstrated promising application prospect of CsCu2I3 and Cs3Cu2I5 MCs in next-generation solid-state lighting.

The concentration effect of Ce3+ ions on the photoluminescence properties of the host sensitized NaMPO4-Ce3+ (M = Mg and Ca) phosphors via solid-state reaction method

A series of Ce3+ doped NaMPO4 (M = Mg and Ca) nanophosphors were prepared using the solid-state reaction route, annealed at 900 °C for 4 h (except for NaMgPO4 which was annealed at 780 °C for 4 h). In this study, the concentration effects of Ce3+ ions for x = 0.0, 0.1, 0.5, 1.0, 1.5 and 2.0 mol% were investigated for its structural and photoluminescence (PL) properties. The structural and PL properties of the NaMPO4:xCe3+ compounds were analyzed using different characterization techniques, such as X-Ray diffraction (XRD), Field Emission Scanning Microscopy (FE-SEM), UV–vis diffuse reflection spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR), PL and International Commission on Illumination (CIE) colour coordinates. XRD results confirm the prepared phosphors were crystallized into monoclinic (NaMgPO4) and orthorhombic (NaCaPO4) structures. SEM results confirm that all prepared samples were formed in the micrometer dimension range, with different sizes and shapes. Energy dispersive X-ray spectroscopy (EDS) spectra confirm the presence of chemical elements in the prepared nanophosphors. The presence of all phosphate (PO43−) and other structural groups were confirmed through FTIR measurements. UV–vis DRS measurements were used to calculate the optical band gap energy values via the Kubelka-Munk function theory. The PLE spectra of the NaMPO4:xCe3+ phosphors were measured in the 200–300 nm range by monitoring their peak at the 385 nm emission wavelength. Using 281 nm excitation wavelength, the PL spectra were measured and a high intensity emission band was found at the 385 nm wavelength (violet colour region). Using PL data of all NaMPO4:xCe3+ ion nanophosphors, the CIE colour coordinates were calculated and were found to lie in the violet colour region of the CIE colour diagram. From all the PL results, it is noticed that enhanced violet colour emissions were observed for all NaMPO4:xCe3+ compounds with increasing Ce3+ ion concentrations, implying that NaMPO4:xCe3+ phosphors are potential candidates for violet colour emitting technologies in display systems.

Synthesis and Characterization of Luminescent Er3+-Doped Natural Fluorapatite

Ca10(PO4)6F2:xEr3+ (x = 0.1, 0.3 and 0.5) was synthesized using solid-state powder process (1150 °C, 1h), conventional sintering (1150 °C, 1h), and spark plasma sintering (SPS) techniques (1150 °C, 10 min, and 50 MPa). XRD analysis revealed that all samples are generally composed of fluorapatite (FAP) containing quartz as a minor phase, and the presence of Er2O3 peaks is becoming more evident as Er-doped increases. In the SEM microstructure images, non-diffused Er2O3 particles also increase with doping in powder and pellet samples. However, the PL analysis showed that the luminescence intensity did not increase proportionally with the doping content caused by the concentration quenching effect. FAP samples doped with 0.3 mol Er have higher luminescence intensity than 0.1 and 0.5 mol Er-doped samples. In addition, powder samples have the highest luminescence intensity due to increased luminescence intensity with increasing crystallite size. The characteristic 2H11/2 to 4I15/2 emission bands of Er3+ at ∼530 nm are seen in all samples. The maximum average lifetime was obtained in 125 μs in the powder sample with 0.3 mol Er. CIE color coordinates demonstrate the standard green color under 275 nm excitation; eventually, these phosphors can be utilized as green phosphors for optical applications.

Synthesis and photoluminescence properties of NaYGeO4:Bi3+ phosphors

In this paper, NaYGeO4:[Formula: see text]Bi[Formula: see text] phosphors were successfully prepared by high-temperature solid-state reaction. XRD patterns and refinement results show that Bi[Formula: see text] ions are successfully incorporated into the matrix material and replaced by Y[Formula: see text]. The emission spectrum shows that the optimal doping concentration of the sample is 0.25%, and it is theoretically studied that the concentration quenching is caused by the nearest neighbor ions. The fluorescence lifetime curve showed that with the increase of Bi[Formula: see text] concentration, the fluorescence lifetime first increased and then decreased. The thermal stability of the sample was studied, and it was found that when the temperature increased to 523 K, the luminescence intensity of the phosphor was still 70% of the initial intensity, and the activation energy was calculated to be 0.306 eV. Finally, the CIE color coordinates of the sample with the best luminous intensity were calculated as (0.1595, 0.0342), and the color coordinates are located in the blue light region.

Environmentally-friendly and low-cost Fe3+-doped broadband NIR light-emitting phosphors

Near infrared (NIR) light emitting phosphors have attracted more and more attention with the development of science and technology. Herein, we report a series of environmentally-friendly low-cost Fe3+-activated ZnGa2O4 phosphors which exhibit intense broadband NIR light emitting. According to density functional theory (DFT) calculations, ZnGa2O4 host possesses an indirect wide bandgap. The emission of the Fe3+-doped phosphors demonstrates a wide band spanning from 650 to 850 nm, with the maximum at 720 nm and a full width at half maxima (FWHM) of 70 nm, showing a large overlap with the absorption of phytochromes (PR and PFR). The luminescence intensity remains at 71% when the temperature is raised to 423 K. The phosphors are fabricated into light emitting diodes (LEDs) which produces strong NIR emission with CIE color coordinates of (0.65, 0.31). All these results suggest that ZnGa2O4:Fe3+ is a promising NIR luminescent material, which is expected to be a candidate for indoor plant culture LEDs.

A 1D helical eco-friendly Mn(II) halide coordination polymer: Luminescent properties involving resonant energy transfer and magnetic characterization

In the present work, we discuss the synthesis of nontoxic Mn(II) halide coordination polymer and explore the potential light emission properties for solar-cell devises through experimental and computational studies. The crystal structure was unveiled through Single Crystal Diffraction, whereas physical properties were investigated by means of thermal, spectroscopic, magnetic, optical and photoluminescence measurements. The observed left-right handed helical structure is built up from an infinite 1-D chains of Mn(II) octahedra. The polymeric network is stabilized through inter-molecular hydrogen bonding interactions and π···π face-to-face interactions. Furthermore, ferro-antiferromagnetic ordering has been proven through magnetic measurements. A deep investigation of the photoluminescence study reveals the presence of a bright bluish light emission with corresponding CIE color coordinates of (0.27, 0.35), CCT value of 8092 K and a very high CRI value of 96. The origin of this intense light emission is mainly attributed to the occurrence of the resonant energy and charge transfer processes between Triazolate ligand and inorganic Mn–Cl sub-lattices. Such behavior leads to the conversion of Frenkel excitons localized within the organic part to Mott-Wannier excitons localized in inorganic clusters. Based on these results, we strongly believe that the elaborated material can be a promising candidate for eco-friendly electronic applications.

Ultra‐Broadband Green‐Emitting Phosphors without Cyan Gap Based on Double‐Heterovalent Substitution Strategy for Full‐Spectrum WLED Lighting

AbstractPhosphor‐converted white light‐emitting diodes (WLEDs) are extensively spread to every part of our daily life and trigger urgent needs for discovery of phosphors without cyan gap (spectral missing in the 480–520 nm range) in pursuit of “human‐centric” sunlight‐like full‐spectrum lighting. Here, a new ultra‐broadband green‐emitting K3La(PO4)2:Eu2+phosphor is reported to meet this challenge. An efficient and positive double‐heterovalent substitution strategy is proved in K3La(Ca/Sr/Ba)(PO4)2:Eu2+by the evidence of enhanced quantum yield, improved thermal stability, and the tunable luminescence color. The luminescence mechanisms are revealed in this paper. Fabricating a dichromatic 370 nm‐UV chip pumped WLED using K3La(Ca)(PO4)2:Eu2+along with a commercially available red phosphor shows a continuity spectrum comparable to the solar spectrum with excellent CIE color coordinates of (0.350, 0.347), low color‐correlated temperature of 4853 K, and high color rendering index (Ra) of 96. It is shown that the double‐heterovalent substitution contributes to designing and optimizing phosphors for full‐spectrum WLEDs.

Synthesis, thermal and photoluminescence investigation of Tb(III) β-diketonates with 1,10-phenanthroline derivatives

The optical and photoluminescent features of octa-coordinated terbium complexes with bidentate 2-benzoylacetophenone (BAP) and 1,10-phenanthroline ancillary ligands have been thoroughly studied. Spectroscopic analyses confirm the binding of Tb3+ with BAP and heteroaromatic auxiliary moiety by means of respective oxygen and nitrogen atoms. Photoluminescence emission plots of all the complexes present sharp peak at 549 nm ascribed to 5D4→7F5 transition, which is accountable for production of green luminescence by ternary complexes upon ultraviolet irradiation. CIE color coordinates also claim green luminescent character of synthesized complexes. All the complexes were found to have high value of color purity. Complexes exhibiting green luminescence and high thermal durability could be useful in manufacturing efficient light conversion devices for lighting systems and display devices.

Modifier’s influence on spectral properties of dysprosium ions doped lead boro-telluro-phosphate glasses for white light applications

Trivalent dysprosium doped Lead boro-telluro-phosphate glasses were synthesized with varying modifiers such as Li+, Zn2+, Ca2+, Sr2+, and Ba2+ using traditional route of glass preparation (melt quenching). The basic network formation and spectroscopical aspects of the as piped outed glasses was analyzed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), UV–vis-NIR, photoluminescence (PL) and emission decay measurements. The existence of elementary functional groups pertaining to the present glass network was explored through FTIR spectral analysis. Bonding parameters (δ) were found to analyze the bonding nature of the rare earth ions and the surrounding metal ligand site. The optical bandgap, band tailing parameter and Urbach energy was found using Tauc’s method in order to identify the transparent region of the prepared glass samples. Furthermore, the symmetry of ligands around the Dy3+ ions has been explored with absorption spectral data by inspecting the Judd-Ofelt (JO) parameters and oscillator strengths of the as-synthesized samples. The radiative properties for instance branching ratios (βR), stimulated emission cross-section (σP) and lifetime (τR) of the meta stable states are estimated to realize the novel applications. The CIE colour coordinates and Y/B ratio values were estimated employing the photoluminescence spectra, whereas the colour purity and it’s colour correlated temperature (CCT) were determined following the (x,y) values thus confirms the generation of neutral white light emitting ability of the prepped samples. The decay or lifetime analysis shows the well fitted non-exponential behavior of the present Dy3+ doped Lead boro-telluro-phosphate glasses.