Emission Bandwidth Research Articles

Synthesis of Mesoporous and Hollow SiO2@ Eu(TTA)3phen with Enhanced Fluorescence Properties.

Lanthanide ions are extensively utilized in optoelectronic materials, owing to their narrow emission bandwidth, prolonged lifetime, and elevated fluorescence quantum yield. Inorganic non-metallic materials commonly serve as host matrices for lanthanide complexes, posing noteworthy challenges regarding loading quantity and fluorescence performance stability post-loading. In this investigation, an enhanced Stöber method was employed to synthesize mesoporous hollow silica, and diverse forms of SiO2@Eu(TTA)3phen (S@Eu) were successfully prepared. Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) outcomes revealed the effective binding of silica with Eu(TTA)3phen through both physical adsorption and chemical bonding. This includes the formation of Si-O-C bonds between silica and the ligand, as well as Si-O-Eu bonds between silica and europium ions. Fluorescence tests demonstrated that the mesoporous SiO2@Eu(TTA)3phen(MS@Eu) composite exhibited the highest fluorescence intensity among the three structured silica composites, with a notable enhancement of 46.60% compared to the normal SiO2@Eu(TTA)3phen composite. The Brunauer-Emmett-Teller (BET) analysis indicated that the specific surface area plays a crucial role in influencing the fluorescence intensity of SiO2@Eu(TTA)3phen, whereby the prepared mesoporous hollow silica further elevated the fluorescence intensity by 61.49%. Moreover, SiO2@Eu(TTA)3phen demonstrated 11.11% greater cyclic stability, heightened thermal stability, and enhanced alkaline resistance relative to SiO2@Eu(TTA)3phen.

Realizing full-spectrum LED lighting with a bright broadband cyan-green-emitting CaY2ZrGaAl3O12:Ce3+ garnet phosphor

Full-visible-spectrum white light-emitting diodes (LEDs) with ultrahigh color rendering index (CRI), which are capable of offering a light source that mimics natural sunlight, have great application potentials in healthy lighting, high-resolution displays, and plant growth lighting. However, cyan gap in the 480–520 nm wavelength range is commonly existed in the emission spectra of traditional phosphor-converted white LEDs, and thus it is urgent to develop high-performance cyan-emitting phosphors to close this spectral gap for realizing full-visible-spectrum LED lighting. Herein, we demonstrate a new efficient cyan-green-emitting Ce3+-activated CaY2ZrGaAl3O12 garnet phosphor for near-ultraviolet (near-UV) pumped full-visible-spectrum warm-white LEDs. The CaY2ZrGaAl3O12:Ce3+ cyan-green phosphor has a cubic structure with the space group Ia3‾d and lattice parameters of a = b = c = 12.39645(8) Å and V = 1886.08(6) Å3. Ce3+ doping concentration dependent luminescence properties have been studied, and the highest emission intensity is obtained at 1 mol%. The optimal CaY2ZrGaAl3O12:1%Ce3+ sample shows a broad excitation band in the 300–490 nm wavelength range with peak at 409 nm due to the 4f→5d transition of Ce3+ ions. Upon 409 nm excitation, CaY2ZrGaAl3O12:1%Ce3+ produces a wide cyan-green emission band in the 425–750 nm spectral range with a peak at 514 nm and a full width at half-maximum of 110 nm owing to the 5d→4f transition of Ce3+ ions, and the corresponding CIE color coordinates and internal quantum efficiency are determined to be (0.2802, 0.4856) and 56%, respectively. Furthermore, the resulting CaY2ZrGaAl3O12:1%Ce3+ phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Finally, a white LED device is fabricated by employing a 395 nm near-UV chip with the phosphor blend of commercial BaMgAl10O17:Eu2+ blue phosphor, as-prepared CaY2ZrGaAl3O12:1%Ce3+ cyan-green phosphor, commercial (Ba,Sr)2SiO4:Eu2+ green phosphor and commercial CaAlSiN3:Eu2+ red phosphor, which exhibits a bright full-spectrum warm-white light with low color correlated temperature of 3334 K and ultrahigh CRI values (Ra = 97, R9 = 95.3, R12 = 90.1) for 20 mA driving current. This work provides a new perspective in designing luminescent materials for high-color-quality full-visible-spectrum LED lighting.

Lanthanide‐doped rare earth nanoparticles for near‐infrared‐II imaging and cancer therapy

AbstractThe optical nanoprobes with emissions in the second near‐infrared window (NIR‐II, 1000–1700 nm) show low tissue autofluorescence and photon scattering; therefore, they provide high spatial resolution and acceptable tissue penetration depth. These advantages make them appropriate for in vivo applications, including bioimaging, NIR‐II triggered disease therapy, and even on‐site efficacy monitoring. Among the various developed NIR‐II fluorescence probes, lanthanide‐doped nanoparticles (LDNPs) exhibit high photo stability and narrow emission bandwidths with long photoluminescence lifetimes and low cytotoxicity; therefore, they have been widely studied in the biomedical field. This review summarizes the typical compositions and optical properties of recently developed NIR‐II emitting LDNPs. Their applications in in vivo NIR‐II bioimaging and cancer therapy are reviewed. The perspectives and challenges of NIR‐II LDNPs are also discussed.

Benzophenoxazine-based colorimetric and fluorescent probe for highly sensitive detection of amines and food freshness

In this work, we reported a chromogenic and near infrared (NIR) region fluorogenic dual-channel probe NRB, which could visually detect gaseous amines with high sensitivity (eg. 50 and 17 ppt for methylamine (MeNH2) via naked eyes and fluorescence spectrometer respectively). It exhibited a wide fluorescent emission band extending to the NIR region with a peak at 615 nm when stimulated by the MeNH2 solution. The plausible sensing mechanism was proved by mass spectrometry, where the reaction process was based on a nucleophilic substitution between the probe and amines rather than the ester group hydrolysis. Furthermore, NRB was successfully applied to monitor the food freshness (seafood and meat food), because of its low cytotoxicity and excellent photophysical properties. It was worth mentioning that real time monitoring for food quality can be realized visually by using a 365 nm UV lamp. In addition, the probe was stable during the quality guarantee period for perishable packaged food. It was believed that the applied experiments have demonstrated the value of this probe in the practical applications for food safety.

Synthesis of ZnO nanowires by thermal chemical vapor deposition technique: Role of oxygen flow rate

Novel catalyst-free synthesis of hierarchical zinc oxide (ZnO) nanowires (NWs) by atmospheric pressure thermal chemical vapor deposition (TCVD) technique and the impact of different oxygen (O2) flow rates (25, 50, 75, and 100 mL/min) on the optical behavior, crystalline structure, emission response, and surface morphology of the prepared samples were studied in detail. The hierarchical ZnO NWs were characterized by ultraviolet–visible (UV–Vis) spectrophotometer, X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and field emission scanning electron microscope (FESEM) measurements. The physical characteristics of the samples were found to be intensely influenced by the O2 flow rate. UV–Vis spectrophotometer measurements indicated that the optical energy gap (Eg) of the samples varies from 3.24 eV to 3.10 eV with regulating O2 flow rates from 25 to 100 mL/min. XRD analyses confirmed that all the prepared samples were polycrystalline in nature with hexagonal wurtzite-type crystal structure and a strong preferential direction along the (002) plane. Photoluminescence results revealed that oxygen vacancies were the major defects causing the blue emissions. Besides, the higher flow rate of O2 (100 mL/min) was efficient in decreasing the number of oxygen vacancies accountable for wide visible emission band intensity. FESEM images demonstrated a high density of hierarchical ZnO NWs with diameters ranging from 33 ± 2 nm to 88 ± 5 nm. Based on the FESEM observations, the potential growth mechanism of the hierarchical ZnO NWs was a vapor-solid (VS) process. Our simple systematic process for growth and characterization may provide toward the development of the hierarchical ZnO NWs-based gas sensors.

Tunable ultralong multicolor and near-infrared emission from polyacrylic acid-based room temperature phosphorescence materials by FRET

Polymer-based room temperature phosphorescence (RTP) materials have received significant attention for their potential application in various fields. However, the development of polymer-based RTP materials with persistent multicolor and near-infrared (NIR) emission still faces great challenges. Herein, 4-carboxyphenylboronic acid (CPBA) is facilely doped into polyacrylic acid (PAA) matrix to construct an ultralong RTP material PAA-CPBA, which is the better candidate of energy donor owing to the wide phosphorescence emission band. Two commercial fluorescent dyes rhodamine B (RhB) and fluorescein (FL) are selected as energy acceptors to prepared ternary systems PAA-CPBA-RhB and PAA-CPBA-FL, and tunable multicolor afterglow from blue to red and yellow is realized through phosphorescence Förster resonance energy transfer (FRET). More interestingly, the quaternary doping system PAA-CPBA-RhB-FL exhibits a nearly white afterglow emission. Significantly, a commercial NIR dye Nile blue (NiB) is used to fabricate the other quaternary doping systems PAA-CPBA-RhB-NiB, and persistent luminescence in NIR region is successfully achieved via stepwise FRET using RhB as an intermediate acceptor. Furthermore, due to the different persistent luminescence performance, the multicolor PAA-based RTP materials are successfully applied in multiple information encryption and multicolor displays.

Growth and spectroscopic properties of a novel Tm3+-doped YSr3(PO4)3 disordered crystal

A novel Tm3+-doped YSr3(PO4)3 (Tm:YSP) crystal with a disordered crystal structure was grown by using the Czochralski pulling method. The single crystal growth, structure, absorption and emission spectra were systematically analyzed. The absorption bandwidth at ∼792 nm was found to be 21 nm, showing that the Tm:YSP crystal was very suitable for commercial laser diodes pumping of AlGaAs. Furthermore, the maximum emission cross section centering at 1835 nm was determined to be 0.86 × 10−20 cm2 with an emission bandwidth of 202 nm, which indicates the promising applications in the fields of ultrafast and tunable lasers. In addition, Spectroscopic parameters, containing Judd – Ofelt intensity, line strengths, radiative transition probabilities, fluorescence branching ratio and radiative lifetime, were analyzed by using the Judd – Ofelt theory. All above results showed that the Tm:YSP crystal with a disordered structure was a potential laser medium in the ⁓ 2 μm region.

Photoluminescence enhancement of Nd3+ doped antimony borate glasses by inclusion of silver nanoparticles

Effect of silver (Ag) nanoparticles (NPs) on photoluminescence (PL) attributes of trivalent neodymium ions bearing glass specimens has been examined and described the outcomes in detail. The presence and distribution of Ag NPs were confirmed using transmission electron microscopic measurement. The luminescence enhancement factor (LEF) for the 1055 nm PL emission peak was boosted from 1.33 to 2.53 when the AgNO3 content elevated from 0.2 to 0.6 mol % and subsequently for 0.8 mol% of AgNO3 the LEF was decreased to 2.38. The stimulated emission cross–section, quantum efficiency, and emission bandwidth magnitudes of PL emission transition of Nd3+ ions located at 1055 nm were increased with elevated inclusion of Ag NPs up to 0.6 mol %. The outcomes instantiate that the inclusion of Ag NPs to the optimized glass composition by 0.6 mol% making it as a beneficial host for optical amplifier and laser functionalities.

Soybean testa spectral study

The increasing production volumes of soy foods require new express methods for testing soybeans during processing and presowing. This study assessed the efficiency of spectral pre-sowing assessment methods using Vilana soybeans.
 The research featured soybeans of the Vilana cultivar. The control sample consisted of untreated whole soybeans while the test samples included soybeans pretreated with various modifiers. The methods involved spectrofluorimetry and IR-Fourier spectrometry.
 A wide emission band at 400–550 nm corresponded to the fluorescence of the soybean testa. The band at 560–610 nm indicated the presence of such modifiers as Imidor insecticide and Deposit fungicide. The luminescence spectrum of the untreated soybean testa was maximal at 441 nm. The luminescence spectrum of the treated soybean samples was maximal at 446.5 and 585 nm when the excitation wavelength was 362 nm. The fluorescence was studied both spectrally and kinetically to establish the maximal luminescence time and the typical vibration frequencies.
 The spectral studies of Vilana soybeans before and after treatment revealed which modifiers were adsorbed on the palisade epidermis and defined the type of interaction between the modifier and the soybean. The spectrofluorimetry and IR spectroscopy proved able to provide a reliable qualitative and quantitative analysis of Vilana soybean surface.

Ultra wideband NIR emission in all-inorganic lead-free metal halides through Sb3+ doping

In recent years, food detection, plant photosynthesis, night vision, and the identification of biological data have all benefited from near-infrared luminescence. However, developing metal halides emitting near-infrared (NIR) light is still difficult, which restricts further applicability. Here, we propose an insightful methodology to investigate the wideband NIR emission in metal halide Cs2ZnCl4 host by doping Sb3+. The phosphors are successfully synthesized by the coprecipitation method and the photoluminescent properties are explored in detail. Based on the spectroscopic information, experimental data with DFT calculations, and luminescence kinetics investigation of Sb3+ doped Cs2ZnCl4, the broadband red emission is caused by self-trapped excitons, which can be attributed to the 3P1–1S0 transitions. The spectra under the excitation at 351 nm exhibit an ultra-wideband emission with a center wavelength of 737 nm, an FHWM of 196 nm, and a significant Stokes shift of 386 nm. The NIR LED fabricated by Cs2ZnCl4: Sb3+ can also be used in night vision devices and biological identification. Our findings in Sb3+ doped Cs2ZnCl4 materials provide light on how doping induces emission centers and expand our understanding of the optical characteristics of doped lead-free metal halides for future research. This work also offers recommendations for broadening the range of uses for luminous metal halides and proposes an efficient method for developing fresh environmentally friendly and wideband emission NIR phosphors.

Advancements in Perovskite Nanocrystal Stability Enhancement: A Comprehensive Review.

Over the past decade, perovskite technology has been increasingly applied in solar cells, nanocrystals, and light-emitting diodes (LEDs). Perovskite nanocrystals (PNCs) have attracted significant interest in the field of optoelectronics owing to their exceptional optoelectronic properties. Compared with other common nanocrystal materials, perovskite nanomaterials have many advantages, such as high absorption coefficients and tunable bandgaps. Owing to their rapid development in efficiency and huge potential, perovskite materials are considered the future of photovoltaics. Among different types of PNCs, CsPbBr3 perovskites exhibit several advantages. CsPbBr3 nanocrystals offer a combination of enhanced stability, high photoluminescence quantum yield, narrow emission bandwidth, tunable bandgap, and ease of synthesis, which distinguish them from other PNCs, and make them suitable for various applications in optoelectronics and photonics. However, PNCs also have some shortcomings: they are highly susceptible to degradation caused by environmental factors, such as moisture, oxygen, and light, which limits their long-term performance and hinders their practical applications. Recently, researchers have focused on improving the stability of PNCs, starting with the synthesis of nanocrystals and optimizing (i) the external encapsulation of crystals, (ii) ligands used for the separation and purification of nanocrystals, and (iii) initial synthesis methods or material doping. In this review, we discuss in detail the factors leading to instability in PNCs, introduce stability enhancement methods for mainly inorganic PNCs mentioned above, and provide a summary of these approaches.

Exciton Emission in Molybdenum Telluride Homobilayers with Fine‐Tuned Twist‐Angles

AbstractLayered 2H‐molybdenum ditelluride (MoTe2) is a promising near‐infrared material with optical activity, which enables hybrid‐integrated with silicon photonics for communication purposes. The use of various artificial hetero‐stacking or twist‐stacking techniques can further expand the emission bandwidth and offer more choices of optical‐active materials used as building blocks in on‐chip optoelectronic devices. However, while the twisting technique is an effective tool for adjusting interlayer interaction in van der Waals materials, a systematic experimental study of twisted MoTe2 homobilayers is currently lacking. Here, a series of MoTe2 homobilayers were prepared with precisely controlled twist‐angles from 0° to 60°, with a particular focus on the small‐twist region. Conducting photoluminescence measurements at low temperatures enabled observation of the evolution of exciton emission as the twist angle increases. Neutral and charged excitons were also identified in a dual‐gated 1.4° twisted MoTe2 through gate‐dependent and field‐dependent photoluminescence measurements. Furthermore, spatially‐resolved photoluminescence measurements revealed the critical role of the interface conditions, including interlayer spacing and strain, in addition to the twist‐angle, in determining the excitonic behavior of the material. This study provides compelling experimental evidence for understanding the twist‐angle‐dependent excitonic behaviors in atomically thin semiconductors.

Temperature-specific spectral shift of luminescing thermally altered human remains

Human bone has shown to have luminescent properties that remain throughout the phases of cremation, with the exception of fully carbonized bone, when excited with a narrow band light source. During this research, an alternate light source (420–470nm, peak at 445nm) was used to visualize and investigate latent details relevant for forensic investigations of human remains recovered at fire scenes. As fire is a destructive force, it induces a vast variety of physical and chemical alterations to all components of the bone, making the subsequent analysis and interpretation of burned human remains challenging. A spectral shift in emission bandwidth, from green to red, was previously observed when the exposure temperature increased from 700 to 800 °C. This spectral shift was reproduced on a total of 10 human forearms, divided into 20 segments, by burning at 700 °C and 900 °C in an ashing furnace. The shift of emission bandwidth caused only by an increase in temperature was furthermore investigated by colorimetric analysis, proving the spectral shift to be significant. By easily quantifying the spectral shift, substantiation is provided for the use of this technique in practice to improve the interpretation of heat induced changes of bone.

Dual-emitting from Bi[formula omitted], Ln[formula omitted] (Ln [formula omitted] Eu, Sm) co-activated Ca[formula omitted]Sb[formula omitted]O[formula omitted] phosphor for optical temperature measurement

In this paper, a series of Ca(2−x−y) Sb2O7: xBi3+, yLn3+ (Ln = Eu, Sm) fluorescent powder samples were successfully obtained, which used the traditional high-temperature solid-phase synthesis method in the preparation process. Samples of Ca2Sb2O7: Bi3+, Ln3+ (Ln = Eu, Sm) fluorescent powder samples were structurally and optically characterized​ using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), photoluminescence excitation spectroscopy and emission spectroscopy, and fluorescence decay measurements. The results show that the prepared Ca(2−x−y) Sb2O7: xBi3+, yLn3+ (Ln = Eu, Sm) samples have an orthogonal spider web structure, which remains unchanged whether Bi3+ is single doped or Bi3+ is co-doped with Ln3+ (Ln = Eu, Sm). Under ultraviolet lamp (λex=340nm) irradiation, Bi3+ doped Ca2Sb2O7 powder shows a wide emission band centered at 435 nm, which is owing to the 3P1→1S0 transition of Bi3+ ion. Therefore, the effect of Bi3+ and Ln3+ (Ln = Eu, Sm) co-doped Ca2Sb2O7 samples on the luminescence intensity of the samples at different concentrations was studied. When the temperature was varied from 293 K to 483 K, the absolute temperature sensitivity (Sa) of doped Bi3+/Eu3+ and Bi3+/Sm3+ phosphors is 0.001K−1 (at 483 K) and 0.02K−1 (at 293 K), respectively, and the relative temperature sensitivity (Sr) is 1.03% K−1 (at 343 K) and 1.19% K−1 (at 293 K), respectively. These results demonstrate that Ca(2−x−y) Sb2O7: xBi3+, yLn3+(Ln = Eu, Sm) phosphors are prospective double emission thermal thermometers.

Spectroscopy and 2.8 µm laser operation of disordered Er:CLNGG crystals.

We report on the first, to the best of our knowledge, laser operation on the 4I11/2 → 4I13/2 transition of erbium-doped disordered calcium lithium niobium gallium garnet (CLNGG) crystals with broadband mid-infrared emission properties. A 41.4 at.% Er:CLNGG continuous-wave laser generated 292 mW at 2.80 µm with 23.3% slope efficiency and a laser threshold of 209 mW. Er3+ ions in CLNGG feature inhomogeneously broadened spectral bands (σSE = 1.79 × 10-21 cm2 at 2.79 µm; emission bandwidth, 27.5 nm), a large luminescence branching ratio for the 4I11/2 → 4I13/2 transition of 17.9%, and a favorable ratio of the 4I11/2 and 4I13/2 lifetimes, exhibiting values of 0.34 ms and 1.17 ms (for 41.4 at.% Er3+), respectively.

High-frequency inlaid cylindrical piezoelectric transducer for high-sensitivity acoustics

This work develops a high-frequency high-sensitivity inlaid cylindrical hydroacoustic transducer by enhancing the electromechanical coupling coefficient, amplifying stress, and adopting circumferential inlaid techniques. Equivalent circuit and finite element simulation methods were used to determine the optimum parameters of the unit, then the transducer was fabricated. Tests show that the resonant frequency of every array unit was 220 kHz. The maximum emission voltage response and reception sensitivity were respectively about 172 dB and −177 dB, with emission and reception bandwidths both about 40 kHz at 3 dB loss. The horizontal and vertical beamwidths were 15° and 4° for each unit respectively.

Light Emission from Single Oxygen Vacancies in Cu2O Films Probed with Scanning Tunneling Microscopy.

Global photoluminescence (PL) and spatially resolved scanning tunneling microscopy (STM) luminescence are compared for thick Cu2O films grown on Au(111). While the PL data reveal two peaks at 750 and 850 nm, assigned to radiative electron decays via localized gap states induced by O vacancies, a wide-band emission between 700 and 950 nm is observed in STM luminescence. The latter is compatible with cavity plasmons stimulated by inelastic electron tunneling and contains no spectral signature of the Cu2O defects. The STM luminescence is nonetheless controlled by O vacancies that provide inelastic excitation channels for the cavity plasmons. In fact, the emission yield sharply peaks at 2.2 V sample bias, when tip electrons are resonantly injected into O defect states and recombine with holes at the valence-band top via plasmon stimulation. The spatially confined emission centers detected in photon maps of the Cu2O films are therefore assigned to excitation channels mediated by single or few O vacancies in the oxide matrix.

Engineering of Cyano Functionalized Benzo[d]imidazol-2-ylidene Ir(III) Phosphors for Blue Organic Light-Emitting Diodes

In this study, we designed and synthesized three series of blue emitting homoleptic iridium(III) phosphors bearing 4-cyano-3-methyl-1-phenyl-6-(trifluoromethyl)-benzo[d]imidazol-2-ylidene (mfcp), 5-cyano-1-methyl-3-phenyl-6-(trifluoromethyl)-benzo[d]imidazol-2-ylidene (ofcp), and 1-(3-(tert-butyl)phenyl)-6-cyano-3-methyl-4-(trifluoromethyl)-benzo[d]imidazol-2-ylidene (5-mfcp) cyclometalates, respectively. These iridium complexes exhibit intense phosphorescence in the high energy region of 435-513 nm in the solution state at RT, to which the relatively large T1 → S0 transition dipole moment is beneficial for serving as a pure emitter and an energy donor to the multiresonance thermally activated delayed fluorescence (MR-TADF) terminal emitters via Förster resonance energy transfer (FRET). The resulting OLEDs achieved true blue, narrow bandwidth EL with a max EQE of 16-19% and great suppression of efficiency roll-off with ν-DABNA and t-DABNA. We obtained the FRET efficiency up to 85% using titled Ir(III) phosphors f-Ir(mfcp)3 and f-Ir(5-mfcp)3 to achieve true blue narrow bandwidth emission. Importantly, we also provide analysis on the kinetic parameters involved in the energy transfer processes and, accordingly, propose feasible ways to improve the efficiency roll-off caused by the shortened radiative lifetime of hyperphosphorescence.

Improving emission performance and bandwidth broadening of the Er3+-doped tellurite – tungsten glasses at 1.5 μm via Pr3+ ions

Tellurite-tungsten glasses doped with Er3+-Pr3+ were fabricated by conventional melt-quenching, increasing the Pr2O3 content to enhance the emission performance and bandwidth of the 1.5 μm emission band. The spectroscopic properties in the visible and near-infrared regions are described, besides the Judd – Ofelt analysis of the Er3+. Results of the 1.5 μm emission intensity of the Er3+ under 980 nm, moreover the up-conversion emission, show an enhancement with the addition of Pr3+. Increments in the FWHM (≈ 90 nm) in the Er3+: 4I13/2 → 4I15/2 band are also reported, where the increment of Pr2O3 content plays an important role. The analyses of the dynamics between Er3+ and Pr3+ in these glasses comprehensively explain the Er3+ emission performance in the visible and near-infrared regions for optical communications applications.

The co-optimization of efficiency and emission bandwidth in GSAGG:Cr3+ NIR ceramic phosphors

The NIR phosphor-converted light-emitting diode (NIR pc-LED) is a new near-infrared light source that has been widely studied. Among various NIR phosphors, Cr3+ doped gadolinium aluminum gallium garnet (GAGG:Cr3+) ceramic phosphor has shown great potential due to its ultra-high efficiency and thermal stability. Despite its capabilities, its detection range may be limited due to a relatively narrow emission bandwidth. To make the GAGG:Cr3+ ceramic phosphors achieve both high efficiency and broadband emission, a series of Gd3Al2-x-yScxGa3O12:yCr3+ (GASGG:Cr3+) ceramic phosphors were prepared. Thanks to the decrease of crystal field strength with the doping of Sc3+, the full width at half maximum (FWHM) of GASGG:Cr3+ ceramic phosphors were extended from 84 nm to 117 nm, and the emission peak exhibited a red-shift of 46 nm. Meanwhile, it still retained extremely high external quantum efficiency (EQE = 47%) and excellent thermal stability (90.7%@150 °C). Then, a NIR pc-LED prototype device was fabricated by combining GASGG:Cr3+ ceramic phosphor with a blue LED chip. The NIR light output power and the photoelectric conversion efficiency of this device achieved 646 mW and 19.2%, respectively. Finally, the application effect in night vision and venography of this prototype device was demonstrated.