Emission Phosphor Research Articles

Brewster-coupling-based thin film filter design for wide-angle high-efficiency phosphor emission.

In this paper, we propose a bandpass filter design method for laser activated remote phosphor (LARP) usage. This design uses the Brewster angle as the passband instead of a wavelength passband. Two advantages are found with this design. First, the transmittance at the Brewster angle is naturally 100%, which is optimal. Second, the stop band reflectance with a wide angular range is better compared to the dichroic filter in a LED-phosphor model. We design two optical thin film filter samples to enhance the extraction efficiency of YAG:Ce phosphor with the same design criteria, objective function, and optimization algorithm. With 50-layer designing, the optical losses for LARP are 23.7% and for LED-phosphor are 26.0%.

Geometrical and Electronic Structure Analysis of Mn‐Doped CaMO3 (M = Ti, Zr, and Sn)

The geometrical and electronic structures of Mn‐doped CaTiO3, CaZrO3, and CaSnO3 deep‐red emission phosphors are investigated both experimentally and theoretically. All the samples are synthesized with solid‐state reaction method by changing the concentration of the doped Mn ions. Crystal structures of the fabricated samples are examined with the powder X‐ray diffraction technique and valence states of the doped Mn ions are determined by measuring the Mn‐L3 X‐ray absorption near‐edge structure (XANES) spectra. Diffuse reflectance spectra are observed to study the change in electronic structures due to the Mn doping. First‐principles calculations are also carried out to investigate geometrical and electronic structures of Mn‐doped CaMO3, in which different types of electron–electron correlation functionals are employed.

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.

Spectroscopic investigation of KBa2(PO3)5:Mn4+ activated glasses for plant cultivation applications

Mn4+ is an impressive activator and sensitizer for luminescent material, which has been comprehensively investigated during the recent decades. In the present work, we give an account of the luminescence properties of Mn4+ activated KBa(PO3)5 glasses are successfully synthesized by using Melt quenching technique. SEM investigation confirms the proposed phosphite glass's morphological behaviour. A photoluminescence research showed that the proposed phosphor's emission peak was positioned in the far red emission area after being excited in the blue region. There are numerous indications that the peaks seen in the 650–750 nm region are helpful for growing plants. Therefore, the suggested glass sample is a promising contender for the use of cultivating far-red emitting plants.

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.

Anti-thermal-quenching in Zn1-xLixGa2O4-δ:Cr3+ phosphor for plant cultivation and optical thermometer based on defect engineering

Excellent thermal stability and appropriate broadband emission of deep red phosphors are indispensable for high-power plant cultivation light emitting diodes. Herein, an anti-thermal-quenching phosphor Zn1-xLixGa2O4-δ:Cr3+ was reported and the defects were introduced into the lattice to enhance the thermal stability via unequal doping. For the representative Zn0.85Li0.15Ga2O4-δ:Cr3+, the emission spectral profile was broadened as two additional emission peaks at around 630 and 675 nm appeared at high temperature and anti-thermal-quenching was observed. Interestingly, [GaO4] tetrahedron and [ZnO6] octahedron appeared as inverted defect and this structure was proved to be partially inverse spinel-structure at high temperature. This anti-thermal behaviour is mainly ascribed to the phase transition between spinel and inverse spinel at high temperature. The emission spectrum of Zn0.85Li0.15Ga2O4-δ:Cr3+ at 423 K agreed well with the absorption peaks of phytochromes. The relative sensitivity of the phosphor was carried out to explore the application in optical thermometer. This simple strategy to create defects opens a new insight to design anti-thermal-quenching phosphors for high-power LEDs and optical thermometer applications.

Design efficient energy transfer Ca2Al2SiO7: Bi3+, Eu3+ phosphors by cationic substitution for full-spectrum W-LED lighting

High lighting quality has become essential in indoor lighting with the continuous technological innovations in the illumination field. The existing mainstream white light implementation cannot completely cover the entire visible light area, whether it is a combination of a blue chip and YAG: Ce3+ (red gap and deep-blue gap) or a combination of an ultraviolet chip and three-color phosphor (cyan gap and deep-blue gap. This study uses Bi3+ as the luminescence center to obtain an efficient deep-blue emission phosphor through local lattice control (Internal Quantum Efficiency = 65%). Subsequently, a Bi3+-Eu3+ energy transfer system with a transfer efficiency of 97.15% was designed to obtain a double emission of deep-blue and red in Ca2Al2SiO7: 0.06Bi3+, 0.04Eu3+ (Internal Quantum Efficiency = 81%). The energy transfer between Bi3+-Eu3+ increases the emission integration intensity to 149% compared to single-doped Eu3+, and the CASO: 0.06Bi3+, 0.04Eu3+ thermal quenching resistance is excellent (3.8% integral strength loss at 425 K). Finally, 395 nm and 310 nm phosphor conversion (pc) W-LED devices with color rendering indexes of 84.2 and 91.6 were prepared by combining CASO: 0.06Bi3+, 0.04Eu3+ and commercially available phosphors, respectively. This result shows that these phosphors can be applied in full-spectrum white illumination.

Infrared to Short-Wave Infrared-Emitting Phosphors for Light-Emitting Diode Applications

In the past decade, near-infrared (NIR) materials have been developed for sensor applications. NIR light-emitting diodes (LEDs) facilitate roadside high-accuracy light detection and ranging, thus enhancing driver safety and confidence. With advancements in wearable technology, individuals, particularly young people, have exhibited a desire to track their own health. Thus, nonintrusive light detection is likely to become the mainstream of detection technology. However, short-wave infrared (SWIR) phosphors are still under development. In the present study, we explored materials with the potential for NIR to SWIR emission, such as Eu2+ (ultrahigh crystal field), Cr3+ (six-fold coordination), and Ni2+ (six-fold coordination) activators. Ni2+ is a suitable SWIR activator; however, its blue light (450 nm) absorption ability is weak. The high-efficiency transfer of energy from Eu2+ and Cr3+ to Ni2+ opens a new avenue for research on SWIR phosphors. We further sorted the materials with high potentials for bioimaging and image recognition applications. SWIR light can penetrate deep into biological tissues and be used to observe the characteristic absorption frequencies of various functional groups. Therefore, SWIR light is used in wearable technology, clinical diagnosis, and chair-side dental checkup. With the help of the artificial intelligence of things technology, image recognition facilitates fast and nondestructive detection. In the future, SWIR phosphors, which help avoid high temperature and working noise, may replace traditional halogen lamps. Our findings reveal the key factors influencing SWIR phosphors and provide insights into the application design. The tunable emission of SWIR phosphors in the 1000–1700 nm spectral range facilitates their widespread applications.

Proximate white light-long phosphor emission and a photoelectrochemical probe from boron defects engineered carbon-nitride nanosheets

A recent surge in the study of a room temperature afterglow nanomaterial has surfaced. Considering its natural coverage of a wide emission spectrum and long afterglow with single light excitation have tinkled many multidisciplinary applications. A synthesis of nanosheets with white light phosphorescence at room temperature is arduous. The manuscript emphasizes on the photoelectrochemical response of room temperature proximate white light phosphorescence in boron carbon nitride nanosheets (BCNs), synthesized at consistent physical operands by varying the overall boron dopant. The study thus envisages the interplay of the participating precursors unfolding the physio-chemical interactions between boron/carbon and nitrogen needed towards the phosphorescence phenomenon. BCNs have provided an immense physio-chemical link between the analyte and photoanode under illuminated conditions, as found vital to achieve the reported sensitivity. Three varying boron conditions are examined, out of which, a 1:4 ratio (BCN-2) is distinguished for remarkable afterglow duration. In addition, the as-synthesized BCN-2 has been used for the photo-electrochemical detection of H2O2 via a differential pulse voltammetry method with a limit of detection of 25 nM. The after-glow property has shown a remarkable response toward H2O2 detection. The easy synthesis and reproducibility of these organic phosphors also prompt its propensity to replace commercially available toxic phosphors.

Highly efficient and self-activating Zn3V2O8 phosphor for the fabrication of cool-white light emitting devices

Achieving an ideal white light with eco-friendly phosphor material with a high quantum efficiency (QE) together with an appreciable correlated color temperature (CCT) and color rendering index (CRI) is considered as a global challenge. To address the issue, we have fabricated a self-activated Zn3V2O8 phosphor-based white light emitting device (WLED) as single emitting compound with desired CCT and color purity values of ∼5074 K and 10.47 × 10−2 respectively, using a moderately low temperature assisted solid-state reaction process carefully ruled out the presence of rare-earth ions. The prepared Zn3V2O8 phosphor exhibited a highly visible yellow (575 nm) photoluminescence (PL) induced by the 3T2 (t152e) →1A1 and 3T1(t152e) →1A1 (t16) transitions of vanadate [VO4]3-, which unveil a significant QE of 67%. The temperature-dependent PL spectra showed a high thermal stability and CIE color coordinates (0.45, 0.47), falling in the exact yellow region. The combination of Zn3V2O8 phosphor and deep blue (405 nm, 40 mW) emission from LED resulted in white light emission with CIE color coordinates and CRI of (0.33, 0.36) and 93, respectively. This work shows that the newly exposed broadband yellow-emitting Zn3V2O8 phosphors as a potential candidate for phosphor-converted WLEDs with high color quality via a non-rare-earth activation approach.

Reducing phosphorus emissions from net cage fish farming by diet manipulation

To alleviate the environmental impact of net cage fish farming in terms of phosphorous (P) emissions to the Baltic Sea, this study aimed at developing and documenting a diet concept for large rainbow trout (Oncorhynchus mykiss) in brackish water (∼15 ppt) that minimizes the excretion of dissolved P and reduces the excretion of particulate P without compromising fish performance and gonadal development. This was to be achieved by reducing the total dietary P content and matching dietary bioavailable P concentrations to fish requirements using whole-body P concentration and expected individual raw material digestibility as criteria. The diet concept was firstly tested in a laboratory mass-balance study with all female rainbow trout (∼1100 g fish−1) fed three commercial-like low-P diets with 0.74% total P, 0.67% total P, or 0.62% total P plus phytase. Comparing the highest and lowest P diets showed that it was possible to reduce the excretion of dissolved P by 87% to 0.08 g dissolved P kg−1 biomass gain without compromising P requirements and fish performance. To verify the concept on commercial scale, an 8 mm P-reduced test diet with 0.63% total P and targeted a bioavailable P concentration of 0.41% by adding phytase was tested against a commercial control diet with 0.81% total P, feeding each diet to four commercial net cages for 5½ months. Harvest data along with ovary and whole-body P analysis confirmed that there were no performance differences between treatment groups, further sustaining that the specific P discharge may be reduced from an estimated 5.1 to 3.2 kg P t−1 fish produced by minimizing the total dietary P content while tailoring the bioavailable P concentration to match fish requirements. Applying the diet concept to the current (2020) Baltic salmonid production could theoretically reduce P emissions by 147 t yr−1 including 79 t dissolved P and 68 t particulate P.

Broadband UV-Excitation and Red/Far-Red Emission Materials for Plant Growth: Tunable Spectrum Conversion in Eu3+,Mn4+ Co-doped LaAl0.7Ga0.3O3 Phosphors.

Broadband ultraviolet (UV) excitation and red/far-red emission phosphors can effectively convert solar spectrum to enhance photosynthesis and promote morphogenesis in plants. Based on the above application requirements, Eu3+ single-doped LaAl1-yGayO3 solid solutions and Eu3+,Mn4+ codoped LaAl0.7Ga0.3O3 phosphors were designed and synthesized in this work. The LaAl0.7Ga0.3O3:0.05Eu3+ (LAG:Eu3+) phosphor exhibits a strong charge transfer band (CTB) excitation and characteristic 5D0 → 7F2 transition red emission (619 nm), which is very similar to the luminescence properties of Eu3+-organic ligand compound (EuL3). Rietveld refinement studies further revealed that the cation substitution disturbs the site symmetry. The optimal Eu3+, Mn4+ co-doped LaAl0.7Ga0.3O3 (LAG:Eu,Mn) phosphor possesses a dual-band excitation spectrum in broadband ultraviolet (UVA, UVB) area and a dual-band emission spectrum within red/far-red area. Under the sunlight radiation, the real-time spectrum of luminous laminated glasses fabricated by coating the LAG:Eu,Mn phosphor shows the percentage of radiant intensity in the red/far-red region significantly increases, suggesting that the phosphor can be a promising candidate for solar spectral conversion in plant cultivation. We believe this work provides a new idea for developing novel broadband ultraviolet excitation and red/far-red emission phosphors.

Development of plastic scintillators doped with silole-based aggregation-induced emission phosphors for scintillation light yield improvement

Plastic scintillators doped with 1,1,2,3,4,5-hexaphenyl-1H-silole (HPS) exhibiting good aggregation-induced emission (AIE) behavior were developed to improve the scintillation light yield. The photoluminescence and scintillation properties of the plastic scintillators containing HPS at the concentration of 0.10–10 mol% were characterized. Plastic scintillators containing HPS exhibited high photoluminescence quantum yields with a high concentration of HPS; additionally, they exhibited concentration quenching tolerance owing to their AIE. Scintillation light yields up to 8200 photons/MeV were achieved at HPS concentrations of 0.50 and 1.0 mol%, and decreased when >1.0 mol% owing to self-absorption. The scintillation decay time constants of the first component were approximately 5 ns at an HPS concentration of >0.5 mol%.

Influence of K/Na ions on structure and luminescence properties of red phosphors K0.5Na0.5Gd(WO4)2: Eu3+

In this paper, we demonstrated the influence of K/Na alkali ions on the structural and photo-cathodoluminescence properties of novel K0.5Na0.5Gd(WO4)2:Eu3+ red phosphor synthesized by the solid-state method. The purity of phosphors is determined from the X-ray diffraction. Rietveld refinement studies confirms that the compounds both K0.5Na0.5Gd(WO4)2:Eu3+ and NaGd(WO4)2:Eu3+ were crystallized in the tetragonal structure with I41/a space group and KGd(WO4)2:Eu3+ was crystallized in monoclinic structure with C2/c space group. The FTIR results indicate that the presence of characteristic functional groups in synthesized samples. The optical bandgap determined from the UV-Visible reflectance spectra in the order K0.5Na0.5Gd(WO4)2:Eu3+ <KGd(WO4)2:Eu3+<NaGd(WO4)2:Eu3+. The photoluminescence excitation spectrum reveal that all the synthesized phosphors can be efficiently excited near UV and Ultraviolet (UV) indicating suitable for solid state display applications. The PL emission spectra indicate the two characteristic emissions located at 614 nm (5D0→7F1) and 590 nm (5D0→7F1) under the excitation of 395 nm. The Judd-Offelt (JO) intensity parameters are calculated to investigate the luminescence behavior and to determine the local structure around the activator related to the Eu3+ ion. The Ω2 > Ω4 of JO parameters indicates the asymmetric environment around the activator suggesting the co-valency of Eu-O bonds with respect to host matrix. Radiative lifetime, branching ratio, electronic dipole transition probabilities were calculated based on the Judd-Ofelt formalism. Cathodoluminescence studies shows the characteristic emission of the Eu3+ ions for low current and voltage which further confirms the pure red color emission of phosphors. All the synthesized phosphors can emit the red emissions with correlated color temperature range from 1500 to 2000 K. For K0.5Na0.5Gd(WO4)2:Eu3+ sample the chromaticity coordinate (x = 0.667, y = 0.329) are closer to the NTSC trichromatic coordinated (x = 0.67,y = 0.33) than that of Y2O2S:Eu3+ suggesting that K0.5Na0.5Gd(WO4)2:Eu3+ can be a potential red phosphor material for warm white LED's applications.

A Deep-Red Emission Phosphor Y2SrAl4SiO12:Ce3+, Cr3+ and Its Utilization in Polycrystalline Silicon Solar Cells

The power conversion efficiency (PCE) of crystalline silicon solar cells has reached a bottleneck. Further improving the PCE is an important current research topic. This Letter reports a new phosphor Y2SrAl4SiO12:Ce3+, Cr3+. Under the excitation in the wavelength range of 320-650 nm, the phosphor Y2SrAl4SiO12:Ce3+, Cr3+ exhibits a deep-red emission in the 500-800 nm range. Due to the energy transfer from Ce3+ to Cr3+, the luminescence intensity of Cr3+ is further enhanced. This matches well with the spectrum of silicon solar cells. Because of the powerful absorption and high internal quantum efficiency, Y2SrAl4SiO12:Ce3+, Cr3+ was used to prepare energy down-conversion (EDC) films. By applying the EDC film on the surface of silicon solar cells, the relative PCE increases by 2.018%. These results indicate that Y2SrAl4SiO12:Ce3+, Cr3+ is an excellent deep-red garnet structured phosphor and furthermore has a positive effect on the enhancement of the PCE of solar cells.

Tunable full-color emission phosphors: Enhanced security application via a patterned 3-dimensions code

Developing tunable full-color emission photoluminescent materials is always desired in color-on-demand applications and still confronts challenges. Theoretically, full color including white emission can be achieved by the combination of three primary colors (red, green, and blue) based on the additive color theory. Herein, a strategy for the preparation of tunable full-color luminescence is realized by mixing the inorganic rare-earth-doped SrAl 2 O 4 : Eu 2+ , Dy 3+ (green emission), Y 2 O 2 S: Eu 3+ , Mg 2+ , Ti 4+ , Ti 4+ 0.05 (red emission), and Sr 2 MgSi 2 O 7 : Eu 2+ , Dy 3+ (blue emission) phosphors with different ratios. By adjusting individual phosphors at certain specific ratios, white light (0.332, 0.332) and full-spectra emission are achieved under a single low excitation energy (λ ex = 365 nm) using a portable ultraviolet (UV) lamp. Based on the facile preparation and effective tunable full-color emission features of the phosphors, a novel encryption way of the luminescent unit as information storage 3 dimensions (3D) codes is developed. The multiplexed encrypting information capacity of the codes is enhanced in a 3D maneuver strategy by simply adjusting the number of light-emitting units with infinite emission colors. The proposed strategy makes the tunable full-color emission phosphors useful in promising applications including full-color display, high-level information encryption and anti-fake.

Tailoring afterglow properties of polychromatic long-persistent LiMg Sr4--2(BO3)3: y Eu2+ phosphor by codoping with Dy3+ or Nd3+

Herein, redshifted long persistent LiMgxSr4-x-2y(BO3)3: y Eu2+, Dy3+(Nd3+) phosphors are successfully prepared in a reducing atmosphere using a high-temperature solid-state process. The emission of phosphors displays redshift characteristics between 633 and 660 nm with an increase in the concentration of Mg2+ substitution, primarily attributed to enhanced energy level splitting of Eu2+ after Mg2+ replacement. The afterglow performance of LiMg0.6Sr3.4-2y (BO3)3: y Eu2+, Dy3+ (Nd3+) samples is enhanced with increase in concentrations of the doped rare-earth ions. An optimal concentration of 6%, the best afterglow performance was achieved because high concentration traps with suitable energy levels were developed; this was confirmed using afterglow measurements and thermoluminescence tests. The Nd3+ codoped phosphor shows improved afterglow performance compared with the Dy3+ codoped phosphor at the same doping concentration, which can be attributed to Nd3+ can easily be incorporated into the borate lattice that generates electron traps with high concentration.

Green emission from trivalent cerium doped LaAlO3/MgO nano-composite for photonic and latent finger printing applications.

A series of Ce3+ doped La1-xCexAlO3/MgO (x = 0, 0.7, 0.9, 1.0 and 2.0 mol%) nano-composites have successfully been synthesized employing the Pechini sol-gel method. XRD profiles assisted with Rietveld refinement results manifested the rhombohedral/face-centered structures of the two phases of the generated composite. Thermogravimetric results corroborate the crystallization temperature of the compound to be 900 °C, that further remains stable up to 1200 °C. Materials have been found to be wide band gap semi-conductors having Eg in the range of 5.5-5.8 eV. Photoluminescence studies reveal their green emission under UV excitation of 272 nm. Application of Dexter's theory and Burshtein model to PL and TRPL profiles, respectively reveals the q-q multipole interlinkages to be the viable cause of concentration quenching beyond optimum concentration of 0.9 mol%. Shifting of the energy transfer route from cross-relaxation to migration assisted mechanism with Ce3+ concentration has also been investigated. Other luminescence based parameters such as energy transfer probabilities, efficiencies, CIE and CCT have also been found to be in an admirable range. From the aforesaid results, it was observed that the optimized nano-composite (i.e. La1-xCexAlO3/MgO (x = 0.9 mol%)) can also be utilized for latent finger-printing (LFP) application that evinces its versatility for photonic as well as imaging applications.

Near ultraviolet light excitable highly efficient blue-green multicolour warwickite phosphor, ScCaO(BO3):Ce3+, Tb3+

Ce3+, Tb3+co-doped multicolour emission phosphors show highly efficient green emission by energy transfer from Ce3+to Tb3+.

UV-excited single-component white phosphor of Lu2WO6 with broad-band emission for pc-WLED.

Obtaining white light from a single-component phosphor is still a significant challenge due to the complex energy transfer between multiple luminescent centers. Herein, white light emission is obtained in a single-component lutetium tungstate without any doping elements. By tuning the pH values during the hydrothermal synthesis, the orthorhombic Lu2W3O12 transformed into monocline Lu6WO12 and rhombohedra Lu6WO12. Only the monoclinic Lu2WO6 phase emitted light, whereas the other two phases did not. The main reason was that the exciton binding energy of Lu2WO6 was larger than that of Lu2W3O12 and Lu6WO12. Except for the 480 nm intrinsic emission of Lu2WO6, new long-wavelength excitation and emission bands were observed with the center at 340 nm and 520 nm. Based on the first-principle calculation, this new photoluminescence band comes from the electron transition between the local states of oxygen vacancies and valence band. Owing to this new broad-band emission, the white light LED lamp is fabricated by combining Lu2WO6 phosphor synthesized at pH values of 4.5 and 6 and 365 nm LED chips. The CIE coordinates of the pc-WLEDs are (0.346, 0.359) and (0.380, 0.380), respectively, and both are located in the white light region. Our research demonstrated a facile way to obtain a single-component white light emission phosphor without any doping components for pc-WLED applications.