Orange-red Emission Research Articles

Structural and photoluminescence properties of Sm3+ ions doped strontium yttrium tungstate phosphors for reddish-orange photonic device applications

In the present research work, Sm3+ ions doped Strontium Yttrium Tungstate (Sr9Y2W4O24) phosphors entitled to emit reddish-orange light have been synthesized using the conventional solid-state reaction method and analyzed their structure and phase using X-ray diffraction (XRD) patterns. The diffraction peaks of the Sr9Y2W4O24 phosphor matches very well with the standard JCPDS pattern with card no. 49-0568. The morphological behaviour of the as-synthesized phosphor has been studied using scanning electron microscopy (SEM). Different vibrational bands present in the titled phosphor have been examined using Fourier Transform Infrared (FT-IR) spectroscopy. The optical band gap values of the as-synthesized phosphors have been measured using diffuse reflectance spectra (DRS). The photoluminescence (PL) spectral features recorded for Sm3+ ions activated Sr9Y2W4O24 phosphor under 405 nm excitation reveal strong visible reddish-orange emission at 604 nm pertaining to the 4G5/2 → 6H7/2 transition of Sm3+ ions. Also the PL spectra show concentration quenching at 2 mol% of Sm3+ ions doped in to them. From the recorded PL spectra, the CIE chromaticity coordinates estimated for Sr9Y2W4O24:2.0mol% of Sm3+ phosphor are falling in deep visible reddish orange region. The PL decay spectral profiles recorded at 604 nm emission under 405 nm excitation are showing double exponential behavior and the experimental lifetimes are found to be decreasing with increase in Sm3+ ions concentration in the assynthesized phosphors. The temperature-dependent PL (TD-PL) measurements demonstrate relatively better thermal stability for the as-synthesized phosphor. All the investigations carried out finally allows us to contemplate the suitability of Sm3+ ions doped Sr9Y2W4O24 phosphor for reddish-orange photonic device applications.

Structural and lattice dynamics investigation of double luminescent nanosized hybrid Gd2O3

A series of cubic Yb3+/Eu3+ co-doped Gd2O3 using melamine as a complexing ligand have been prepared by low-temperature treatment at 200 °C. Structural and lattice dynamics have been done using XRD and Raman analysis. Photoluminescence analysis of the co-doped Gd2O3 samples is performed at 220, 275, and 980 nm excitations and the plausible mechanism is discussed in detail. The Eu3+ ions asymmetric ratio is calculated as 2.254 in Yb3+ co-doped Gd2O3 lattice. Luminescence lifetimes oscillate between 3.83 and 739 µs. Spectral parameters and J-O intensity parameters are calculated for all co-doped Gd2O3 NPs. Electric-multipole interaction is the energy transfer mechanism responsible for concentration quenching with a critical distance of 11.45 Å in Gd2O3: Yb3+(20 mol%), Eu3+(5 mol%) nanoparticles (NPs) on 980 nm excitation. The sample emits near-white, blue, and orange-red light emissions and can be utilized for bio-labeling applications. Temperature-dependent studies on Gd2O3: Yb3+ (20 mol%), Eu3+ (5 mol%) NPs are performed in the temperature range of 303–478 K. The developed NPs exhibit paramagnetism with a value of 1.580 emu/g owing to Gd3+ intrinsic magnetic moments.

Luminescence and spectroscopic studies on Eu3+-doped borate and boro-phosphate glasses for solid state optical devices

An addition of Eu3+ ions in Borate glasses (7TiO2 + 3Al2O3 + (60−x)B2O3 + xEu2O3 + 5LiCO3 + 25SrCO3) (where x = 0.05, 0.10, 0.15, and 0.20 mol%) and Boro-phosphate glasses (40B2O3 + 3Al2O3 + (10−x)P2O5 + xEu2O3 + 7ZnO + 5LiCO3 + 10H6NO4P + 25SrCO3) (where x = 0.10 and 0.20 mol%) containing heavy metals, alkali, and alkaline were prepared using a conventional melt quenching technique. The complementary study of the FT-IR and FT-Raman spectroscopic studies proposed the conversion of BO3 ⇔ BO4 in the borate glass network, and the exchange of the PO3 ⇔ PO2 in the boro-phosphate glass network by increasing the Eu3+ ion concentration. The optical characteristics including absorption, linear refractive index (n), Urbach energy (Eu), direct and indirect band gap energies of the prepared glasses were examined and discussed. Judd-Ofelt (JO) theory was used to determine radiative spectroscopic properties such as radiative transition probability (AR), luminescence branching ratio (βR) and stimulated emission cross-section (σPE). Theoretically, the optical gain parameter and gain bandwidth were calculated, which shows their vital role in laser applications. Using CIE chromaticity coordinates, the reddish orange light emission was observed as a proportion of the increase in Eu3+ ions concentration in both glass networks. The measured colour coordinates were utilised to evaluate the correlated colour temperature (CCT), colour purity (Pc), and excitation purity (Pe) of the studied glasses.

Photoluminescence and thermoluminescence kinetic features of Eu3+ doped Sr2YVO6 double perovskite phosphor

Through traditional high-temperature combustion synthesis, a series of luminescent orange-red emitting Sr2YVO6:Eu3+ double perovskite phosphors were prepared, and their luminescence properties were examined. Through X-ray diffraction (XRD) and Rietveld analysis, the monoclinic crystal structure of all prepared Sr2YVO6:Eu3+ phosphors were confirmed. Scanning electron microscopy (SEM) was used to analyse the morphology of the phosphor. Under 320 nm excitation, Eu3+ doped Sr2YVO6 phosphors exhibit very strong red photoluminescence (PL) emission bands at 595 nm, 616 nm and 620 nm as well as distinct red emission bands at 653 nm and 699 nm, which are originated due to the 5D0-7FJ (J = 1,2,3,4) transition of Eu3+. A series of phosphor also exhibit orange-red emission at 595 nm, 612 nm, 616 nm and 620 nm under the excitation wavelength of 396 nm. High color purity of the phosphors is revealed by calculated color purity and excellent chromaticity coordinates, which also confirms the presence of far-red luminescence emission. After the irradiation of the phosphors at various beta doses via 90Sr/90Y beta source, the thermoluminescence (TL) studies of Eu3+ activated Sr2YVO6 phosphors was conducted. Exposer of beta irradiation revises a prominent TL glow curve at 124 °C with a small hump at around 290 °C, indicating the development of different trap centres in the phosphor. As the dose of beta radiation increased, a linear dose response was observed in TL intensity. Computerised Glow Curve Deconvolution (CGCD) method and Chen's Peak Shape Method (PSM) were used to determine the activation energies and trapping parameters of TL glow curves. According to CGCD fitting of TL glow curves, it is found that all glow curves consist of five deconvoluted peaks, which follows general order kinetics. Activation energies calculated through different methods were comparable and significant.

Push-Pull Bridged Distyrylbenzene with Highly Bright Solid-State Red-Orange Aggregation-Induced Emission.

Multiple emission colors in solid-state organic fluorophores with the same main skeleton are essential for improving the performance of light-emitting devices/materials. Specifically, emission in the red/near-infrared region is of great importance in the biological field. Previously, we developed di-bridged-distyrylbenzene DBDB[7] with high-brightness solid-state blue and aggregation-induced emissions (AIE) by introducing the bridging structures of a seven-membered ring into the vinylene groups of distyrylbenzene (DSB). Herein, we synthesize MNDBDMeODB[7] (1), which features substituted methoxy and malononitrile groups as donor and acceptor groups, respectively, in DBDB[7]. In solvents more polar than THF, MNDSDMeOB (3), which has the same main skeleton as 1 but without bridges, shows no emission in the solid state, whereas 1 exhibits highly bright red-orange emission in the solid state owing to the suppression of intermolecular electronic interactions by the bridges and the AIE property. We also synthesize MNDSD(EHO)B (2) in which the methoxy groups of 3 are replaced by ethylhexyloxy groups, thus disrupting the crystallinity of the molecule. 2 exhibits positive fluorescence solvatochromism and has a high fluorescence quantum yield in the solid state as a red-emitting DSB derivative. The solid-state emission properties of 1 and 2 will improve the applicability of DSBs and functionalities of light-emitting devices/materials.

Structural and luminescent features of warm reddish-orange light-emitting Sm(III) doped Gd2Si2O7 nanophosphors for near UV-energized LEDs

Solution combustion (SC) synthetic method was used to prepare warm reddish-orange light emitting Gd2-xSi2O7:xSm3+ (x = 1–5 mol%) nanophosphors. Structural analysis was performed to recognize the phase identification. The nanomaterials were structured into triclinic phase with P-1 space group. All the diffraction peaks are fairly matched with the standard data and (h k l) planes have been well indexed. Additionally, the evidence about the site symmetry around Sm3+ ions have been prejudiced by considering the intensity ratio of 4G5/2→6H9/2 (electrical dipole) to 4G5/2→6H5/2 (magnetic dipole) transitions. The highest emission at ∼597 nm is accountable for reddish-orange light emission in the doped nanocrystalline materials. Among different excitation, the most intense excitation peaking at ∼402 nm lies in the near UV range, which specifies that the designated phosphors could be competently energized through NUV based LEDs.

Excellent photoluminescence and electrochemical properties of Sm3+ doped Ca2MgSi2O7 nanophosphor: Display and electrochemical sensor applications

A series of orange-red light emitting Ca2MgSi2O7:Sm3+ nanopowders were fabricated via low-cost eco-friendly green combustion technique using Aloe vera gel as fuel. The phase purity of the samples were confirmed by the powder X-ray diffraction (PXRD) technique. Pure single-phase tetragonal structure is observed from the PXRD results with no additional impurity peaks. The band gap energy of the fabricated powders was estimated by diffuse reflectance spectra (DRS) and is found to be in the range of 4.01–5.98 eV. A high resolution scanning electron microscope (SEM) was used to study the morphological behaviour of the samples. Honeycomb-like structures are observed from the SEM results. The particle size was evaluated by transmission electron microscopy (TEM) and is found to be ∼50 nm. The interplanar distance is found to be 0.53 nm. Photoluminescence properties were systematically studied in detail. The phosphors are successfully excited at 403 nm NUV light, producing reddish-orange characteristic emission. The emission peaks are centered at 558 (4G5/2 → 6H5/2), 607 (4G5/2 → 6H7/2) and 645 nm (4G5/2 → 6H9/2), respectively. Among the observed peaks the red emanation (4G5/2 → 6H7/2) is stronger than the orange emission (4G5/2 → 6H5/2) in the current investigation. The photoluminescent concentration quenching is noticed above 5 mol% Sm3+ ion doping content. The dipole–dipole interaction resulting in cross relaxation is found to be the principal cause of concentration quenching mechanism. The color features such as Commission Internationale de l’Eclairage (CIE) and correlated color temperature (CCT) were studied in detail. The optimized chromaticity coordinates were estimated to be (0.6363, 0.3632), which fall in the reddish-orange region. The average CCT value obtained is 3362 K. The average color purity is found to be ∼82%. Sm3+ incorporated Ca2MgSi2O7 samples are possible contender for single white light generation commercial candidates owing to their strong hypersensitivity of Sm3+ ions through host, least possibility for re-absorption of blue-green emission owing to poor direct f–f excitation of Sm3+ ions, and high color purity (reddish-orange emission). The prepared powders exhibit excellent electrochemical redox properties and CPE modified optimized powders show outstanding sensitive response which indicates its use in the potential electrochemical sensor materials for drug sensing studies.

Wide colour tunability through cross relaxation and energy transfer in a Eu3+/Tb3+:ZnGa2O4 phosphor

In this article, the Tb3+, Eu3+ activated/co-activated ZnGa2O4 phosphors were synthesized using solid state reaction method to study the structural and optical characteristics. The XRD and SEM techniques, were used to study the crystallinity, phase purity and particles size whereas the EDS measurement approved the existence of different elements present in the phosphor samples. The FTIR and diffuse reflectance spectra of phosphor samples were studied to know the phonon frequency and the optical band gap. The PLem spectra of Tb3+ activated ZnGa2O4 phosphor contain blue, green and orange red emissions on 378 nm excitation. A colour tunability from blue to green regions was seen to arise due to cross relaxation on increasing the concentrations of Tb3+ ion. The Eu3+ activated ZnGa2O4 phosphor exhibited a strong red emission under 393 nm excitation. Further, the Eu3+ activated ZnGa2O4:Tb3+ phosphor showed colour tunability from blue to bluish white and from green to red under 260 and 378 nm excitations, respectively. Moreover, an energy-transfer (ET) has been observed from Tb3+ to Eu3+ ions with energy transfer mechanism as dipole-dipole interaction. The ET efficiency for 0.8 mol% Eu3+ in ZnGa2O4:0.05 Tb3+ phosphor has been found 97%. Under 260 nm excitation, the Eu3+/Tb3+ co-activated ZnGa2O4 phosphor also emits blue, green and red bands. Thus, the Tb3+, Eu3+ co-activated ZnGa2O4 phosphor may be useful for solid-state lighting applications.

Luminescence from metal-oxide-semiconductor devices with Eu3+-doped CeO2 films on silicon: From broadband to monochromatic emission

We report on the transformation from broadband to monochromatic orange-red emission for the electroluminescence (EL) from the metal-oxide-semiconductor (MOS) devices with europium (Eu3+)-doped CeO2 films annealed at various temperatures as the light-emitting layers. Under the bias voltages exceeding 8 V, the 800 °C-annealed MOS device exhibits dominant Eu3+-related emission at 590 nm with a full width at half maximum of only ∼2 nm. In contrast, the 400 °C-annealed MOS device is activated into broadband emissions associated with the defects in the CeO2 host. Also, the two distinct EL behaviors can co-exist by annealing the CeO2:Eu3+ film at 600 °C. It has been demonstrated that the defect- and Eu3+-dependent EL are related to the Poole-Frenkel (P–F) and trap-assisted tunneling (TAT) electrical conduction mechanisms, respectively. The MOS device with a tunable EL is significant due to its potential applications, e.g., optoelectronic integration.

Crystal Chemistry and Photoluminescent Aspects of Bright Orange Light Emitting Sm3+- Activated Ba2BiV3O11 Nanomaterials for Advanced Illuminating Applications.

In the present system, Sm3+ activated Ba2BiV3O11 nanomaterial series radiating orange-red light was developed via an efficient approach of solution combustion method. The structural examinations using XRD analysis indicate that the sample is crystallized into the monoclinic phase with the P21/a (14) space group. The elemental composition and morphological conduct were studied via energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) respectively. Also, the formation of nanoparticles was confirmed by transmission electron microscopy (TEM). Photoluminescent (PL) examinations reveal the orange-red emission from the developed nanocrystals via documenting the emission spectra, which reveals the peak at 606nm due to the 4G5/2 → 6H7/2 transition. Further, the decay time, non-radiative rates, quantum efficiency, and band gap of the optimal sample were computed as 1.3263 ms, 219.5s- 1, 70.88%, and 3.41eV respectively. Finally, the chromatic parameters including color - coordinates (0.5565, 0.4426), 1975K color correlated temperature (CCT), and color purity (85.58%) reflected their excellent luminous performance. The above-mentioned outcomes endorsed the relevancy of the developed nanomaterials as a propitious agent in the engineering of advanced illuminating optoelectronic appliances.

Orange-red emitting Sr3LaTa3O12:Sm3+ phosphors with perovskite structure and high thermal stability for w-LEDs

A novel layered perovskite tantalate phosphor Sr3LaTa3O12:Sm3+ (SLTO:Sm3+) with orange-red emission was obtained for the first time via the solid-phase synthetic method. The phase purity, surface morphology, element distribution and luminescent properties of the SLTO:xSm3+ (x = 0.01 mol%–0.30 mol%) phosphors were investigated. Under 408 nm excitation, the optimum doped SLTO:0.10Sm3+ phosphor emits orange-red light at 598 nm with the highest emission peak (4G5/2 → 6H7/2). The critical energy transfer distance is 1.687 nm. The prepared SLTO:0.10Sm3+ phosphor has excellent thermal stability with temperature quenching temperature (T0.5 > 500 K) and high activation energy (Ea = 0.25 eV). Through calculation, the chromaticity coordinates of all samples are concentrated in the orange-red area, and the color purity reaches 99%. The fabricated white light-emitting diode (w-LED) has a good correlated color temperature (5132 K), a high Ra (89), and the CIE chromaticity coordinates (0.340, 0.327). Consequently, the superiority of orange-red-emitting tantalate SLTO:Sm3+ phosphors for w-LEDs is demonstrated.

Exploring the orange–red emission from novel vanadate-based nanomaterials for highly innovative photonic applications

Exploring the orange–red emission from novel vanadate-based nanomaterials for highly innovative photonic applications

Comparison of the emission wavelengths by a single fluorescent dye on in vivo 3-photon imaging of mouse brains

Multiphoton microscopy (MPM) is a powerful imaging technology for brain research. The imaging depth in MPM is partly determined by emission wavelength of fluorescent labels. It has been demonstrated that a longer emission wavelength is favorable for signal detection as imaging depth increases. However, there has been no comparison with near-infrared (NIR) emission. In order to quantitatively analyze the effect of emission wavelength on 3-photon imaging of mouse brains in vivo, we utilize the same excitation wavelength to excite a single fluorescent dye and simultaneously collect NIR and orange-red emission fluorescence at 828[Formula: see text]nm and 620[Formula: see text]nm, respectively. Both experimental and simulation results show that as the imaging depth increases, NIR emission decays less than orange-red fluorescent emission. These results show that it is preferable to shift the emission wavelength to NIR to enable more efficient signal collection deep in the brain.

Broadband-sensitive up-conversion in Ni2+/Er3+ co-doped Gd2MgTiO6

Ni2+ doped and Ni2+/Er3+ co-doped Gd2MgTiO6 (GMT) phosphors have been synthesized by conventional high-temperature solid-state reaction method. First-principles calculation and X-ray diffraction analysis proves that Ni2+ ions occupy the Mg2+ sites in the Gd2MgTiO6 matrix at low Ni2+ doping concentration and begin to occupy Ti4+ sites at high Ni2+ doping concentration. The near infrared emissions of Ni2+ ions occupying Mg2+ and Ti4+ sites peak at 1344 nm and 1412 nm, respectively, forming a broad near infrared emission band from 1100 nm to 1700 nm. It is found that Ni2+/Er3+ co-doped Gd2MgTiO6 phosphor is capable to up-convert near infrared photons in the wavelength range of 870–1700 nm to visible 532 nm, 555 nm and 666 nm emission, caused by the energy transfer sensitization process from Ni2+ to Er3+. The Ni2+ and Er3+ concentration dependent up-conversion properties have been investigated and it is found that the Gd2MgTiO6: 2%Ni2+/5%Er3+ phosphor shows the strongest up-conversion emission, in which the energy transfer efficiencies from the Ni2+ ions occupying Mg2+ and Ti4+ sites to the Er3+ ions are 81.5% and 79.3%, respectively. The Gd2MgTiO6: 2%Ni2+/5%Er3+ phosphor shows yellow emission under the irradiation of 1342 nm and 1550 nm lasers, and green and orange-red emissions under the irradiation of 980 nm and 1064 nm laser, respectively. The broad band excitability and multi-color up-conversion performance of the Ni2+/Er3+ co-doped Gd2MgTiO6 phosphor suggest that it has wide application prospect in anti-counterfeiting, solar cell efficiency enhancement, infrared detection and so on.

Structural, photoluminescence, and thermoluminescence behaviors of Samarium doped CaWO4 phosphor

This manuscript reports the crystal structure, photoluminescence and thermoluminescence behavior of Samarium doped CaWO4 i.e., Ca1-xSm2x/3WO4 (x: 0.01, 0.02, 0.03, 0.04, 0.05) synthesized by conventional solid state reaction method. The X-ray diffraction data are analyzed using Rietveld refinement method and showed that samples exhibit cento-symmetric tetragonal crystal structure with I41/a (No. 88) space group. The unit cell volumes are increased with rising Sm composition. The energy bandgaps of the phosphors are observed by the UV–Visible absorbance spectroscopy and found to be directly proportional to the cell volume. Photoluminescence properties are considered from the excitation as well as emission spectra. These spectra resulted that the critical quenching concentration occurred at x = 0.02 due to the dipole–dipole interactions with critical energy transfer distance of 20 Å. The color purity and correlated color temperature values of the sample can be measured from the CIE Chromaticity. It is also described the orange-red emission color of the phosphors. Lower UV dosimetry with second order kinetics is obtained from the thermoluminescence spectra of x = 0.02 with 30 min UV radiation.

Novel red-emitting Cd2MgTeO6:Eu3+ phosphors with an abnormal thermal quenching for application in w-LEDs and potential fingerprint detection

A new series of red luminescent Cd2MgTeO6:xEu3+ (x = 0.5–50 mol%) phosphors was successfully synthesized through a high-temperature solid-phase reaction at 1000 °C. The synthesized phosphors were investigated for their phase purity, surface morphology, elemental distribution, and luminescence properties. Strong orange-red light emission (617 nm) was observed upon excitation at 398 nm, which was attributed to the electric dipole 5D0-7F2 transition of Eu3+. The optimal doping concentration was found to be x = 20 mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of all the Cd2MgTeO6:Eu3+ samples were found to be located in the red region and were almost the same. The Cd2MgTeO6: 20 mol%Eu3+ phosphors exhibited an unusual thermal quenching behavior, maintaining 102% of the initial intensity, thus possessing excellent thermostability. Moreover, the manufactured white light diode demonstrated a good color rendering index (Ra = 89) with the coordinates of (0.344, 0.330) by the Commission International de L'Eclairage (CIE). Additionally, the Cd2MgTeO6: 20 mol%Eu3+ phosphor was surface-functionalized with oleic acid (OA) (Cd2MgTeO6: 20 mol%Eu3+@OA) to aid in the identification of Level I-III fingerprint details with high resolution and contrast. Good visualization of the latent fingerprint (LFP) was observed on different substrates. Therefore, Cd2MgTeO6:Eu3+ phosphors hold great promise for the visualization of w-LEDs and LFPs.

Blue light induced red phosphors Sr2CeO4:Eu3+ through co-doping with M2+ (Mg, Ba, Ca) and spectroscopic properties applied in WLEDs

In the present work, A series of Sr2CeO4:xEu3+ (x = 0.15, 1, 2, 5 mol%) (SCO:xEu3+) and co-doped with different divalent metal ions (M2+: Mg, Ca, Ba) phosphors were successfully synthesized through traditional hydrothermal method. All the samples performed pure Sr2CeO4 phase. The absorption spectra show that an overlap between Ce4+–O2- CTS band and Eu3+ ions results in the energy transfer from the matrix to the emitting center. With the concentration of Eu3+ ion increasing, the phosphors exhibit orange red emission, and the highest intensity was achieved when the Eu3+ concentration was 2 mol%. The energy transfer mechanism would be dipole–dipole interaction. Furthermore, when the concentration of Eu3+ ion is at 2 mol%, the samples co-doped with M2+ ion performed intense red emission of Eu3+ ion under 467 nm excitation, which is ascribed to M2+ ions disturbed the anisotropic structure to create defects so that make much more efficient energy transfer from Ce-O band to Eu3+ ions. Moreover, CIE chromaticity showed SCO:2%Eu3+/2%M2+ phosphors performed pure red warm light. The above results suggest that SCO:2%Eu3+/2%M2+ can be of potential as red-emitting phosphor for blue-excitation WLEDs.

Large electrostrain and strong photoluminescence in rare-earth-modified (Na0.5Bi0.5)TiO3-based lead-free piezoelectric ceramics

Rare-earth (RE)-doped ferroelectric materials have received much attention due to their good performance with combined excellent luminescence and electrical properties. In this work, we report multifunctional features with large electrostrain and strong photoluminescence in (Na0.5Bi0.5)TiO3-based lead-free piezoelectric ceramics. By introducing RE3+ (RE = Sm, Pr, Eu) ions as activators into the host material with the composition of (Bi0.5Na0.5)0.94Ba0.06Ti0.98(Fe0.5Nb0.5)0.02O3 (BNBT-FN), the ceramics gradually adopts a higher structural symmetry, leading to the destruction of the long-range ferroelectric order, which is conducive to the electrostrain response. When the RE3+ content is 0.6 mol.%, the ceramic samples exhibited large unipolar strains of 0.34–0.39% and high electrostrictive coefficients Q33 of 0.021–0.029 m4/C2 under an electric field of 80 kV/cm. Furthermore, due to the luminescence activity of the RE3+ ions, the samples exhibited strong red or reddish-orange emission and simultaneously showed good temperature sensing behavior. These results suggest that the RE3+-doped BNT-based materials have great application potential in multifunctional devices.

α-Ba2ScAlO5: Eu3+ as a promising thermally stable orange-red emission phosphor

The thermal quenching effect of phosphors restricts the practical application due to the serious energy loss. Herein, excellent thermal stability of Eu3+ emission is observed in the α-Ba2ScAlO5:xEu3+ phosphors. The compounds crystallize in the hexagonal sole-phase structure with partial replacement of Sc3+ by Eu3+. Apart from the 4f6→4f6 transitions, luminescence excitation spectra of α-Ba2ScAlO5: xEu3+ show an intense charge transfer band (CTB). Upon excitation into the CTB, the emission of Eu3+ shows normal thermal quenching with intensity at 210 °C keeping 70% of that measured at room temperature. When excited into the characteristic line at 393 nm, the emission of Eu3+ demonstrates even better thermal stability while photoluminescence intensity declines by only 5% at 210 °C compared to that at room temperature. The CTB is shown to play a role of an intermediate level to impact the energy transfer mechanism responsible for excellent thermal stability.

Anionic Regulation toward Bi3+ Selective Occupation for Full-Spectrum White Light Emission.

An activator's selective occupation of a host is of great significance for designing high-quality white light-emitting diode phosphors, while achieving a full-spectrum single-phase white light emission phosphor is challenging. In this study, a boron phosphate solid-solution Na2Y2(BO3)2-x(PO4)xO:0.005 Bi3+ (NYB2-xPxO:0.005 Bi3+) white phosphor was designed by selectively occupying Bi3+ activators in the mixed anionic groups. The substitutes of the anionic unit (BO3)3- by the (PO4)3- unit are supposed to force part of the Bi3+ ion to enter the Na lattice site, which produces an intense orange-red emission peaked at 590 nm. In parallel, spectral tuning from blue to white light and an internal quantum efficiency of 56.42% was obtained, and the thermal stabile luminescence intensity remains at 94.2% of the initial intensity after four heating-cooling cycles from 30 to 210 °C (luminescent intensity is 83.6% of room temperature (RT) at 150 °C, with excellent thermal stability and recovery performance). Finally, an excellent color rendering index (Ra = 90.8 and R9 = 85) was demonstrated for white light-emitting diode devices using only an NYB1.5P0.5O:0.005 Bi3+ phosphor and a near-ultraviolet (n-UV) 365 nm LED chip. This work delves into the different selective occupancy of Bi3+ ions and explores a new avenue for the design of phosphors for full-spectrum white light emission.