Decrease In Luminescence Intensity Research Articles

Study on the modulation of luminescence peak position and luminescence mechanism of black phosphorus

The application of black phosphorus in optoelectronic devices is hindered because of its inherent band gap characteristics. In the paper, black phosphorus was prepared by high-energy ball milling, and its related structure and properties were characterized. At the same time, the luminescence mechanism of black phosphorus was explored, and the effect of ultrasonic time on the structure and optical properties of black phosphorus was studied. The luminescence peak of black phosphorus can be modulated to the visible light range after adding polyethylene glycol, and the luminescence of black phosphorus is closely related to the P (020) and P (021). It was found that the luminescence intensity of alcoholized black phosphorus decreases with the increase of ultrasonic time. When the ultrasonic time is 15min, the luminescence intensity of alcoholized black phosphorus decreases greatly, this is because that the content of P (020) in black phosphorus decreases with the increase of ultrasonic time, resulting in the decrease of luminescence intensity.

Controlled growth of MPA-capped ZnS quantum dots through concentration-modulated single injection hydrothermal method

This study presents the controlled growth of 3-Mercaptopropionic acid (MPA)-capped ZnS quantum dots (QDs) using a concentration-modulated single injection hydrothermal method. Employing the Concentration optimization by optical spectra (COOS) method, we optimized the MPA:Zn:S ratios to investigate the influence of the capping agent, cation, and anion for exceptional properties suitable for optoelectronic and sensor applications. CMSIH operates as a single-step synthesis process, reducing processing time and complexity. This streamlined approach not only enhances efficiency but also minimizes the risk of contamination and ensures batch-to-batch consistency in QD production. Its moderate operating conditions, compared to other high-energy methods, also contribute to reduced energy consumption and environmental impact, aligning with sustainable manufacturing practices. Further, X-ray diffraction (XRD) confirmed the Zinc blend (cubic) phase of ZnS, and Fourier-transform infrared spectroscopy (FTIR) validated MPA capping. The QDs exhibited strong quantum confinement, causing a blue shift in absorption peaks compared to bulk ZnS. Higher MPA concentrations ranging from 0.02 M to 0.1 M induced a red shift in the absorption edge due to prolonged reaction times and strong cation binding by MPA. Variations in cation Zn and anion S ratios from 0.02 M to 0.1 M caused blue and red shifts in the absorption edge, respectively. For instance, Zn:S = 0.04:0.01 M increased cation concentrations, reducing QD size up to 0.67 nm, while enhanced anion concentrations Zn:S = 0.04:0.04 M enlarged the QDs size up to 2.35 nm. Remarkably, calculated QD sizes using Brus’ equation were smaller than the Bohr radius, even at an elevated temperature of 95 °C, indicating significant quantum confinement. Luminescence studies revealed reduced luminescence with higher MPA concentrations, increased luminescence intensity with higher cation Zn+ concentrations, and a red shift in the luminescence peak with higher anion S concentrations. As the temperature rises, there is an observable decrease in luminescence intensity. Furthermore, the investigation into the relationship between chemical composition and optical properties of MPA-capped ZnS QDs at elevated temperatures expands understanding of quantum confinement effects. The synthesised unique ultra small ZnS QDs can be used in advanced quantum sensors mainly as radiation detectors.

Lanthanide-grafted covalent organic framework as a colorimetric and luminescence dual-mode nanoprobe for tetracycline detection

Tetracyclines (TCs) are a group of antibiotics commonly using for infection treatment, however, the leftovers in potable water and food which are derived from the abuse of TCs lead to the adverse human health and environmental impacts. Herein, we developed a lanthanide-grafted covalent organic framework (COF) as a colorimetric and luminescence dual-mode nanoprobe to realize precise, sensitive, rapid, real-time TC determination. Ce3+, Eu3+ ions were chosen to functionalize COFs due to their particular corresponding catalytic and luminescent characteristic for bimodal sensing. COF-Ce-Eu can work as an enzyme mimic to catalytically oxidize the substrate of 3,3′,5,5′-tetramethylbenzidine (TMB) with existence of H2O2, besides, the addition of TC is conducive to promote the pristine catalytic activity as the formation of complexation of COF-Ce-Eu with TC. The catalytic activity and the absorbance of COF-Ce-Eu directly correlate to TC concentration. The ratiometric luminescence response was established on the intensity ratio of the broad band centered at 512 nm originated from the matrix COF and the sharp peak at 616 nm originated from Eu3+. The decrease in luminescence intensity of the peak at 512 nm and the increase at 616 nm depended on TC concentration. This colorimetric and luminescence dual-mode platform exhibits excellent selectivity and sensitivity towards TC, with a wide linear range of 0–50 μM, and low detection limits of 24 nM and 3.4 nM, respectively. The designed bimodal sensing strategy provide a promising double assurance for the accurate trace of TC in food and water samples.

First principles calculations of structure, vacancy defects, thermodynamic and mechanical properties and near-infrared luminescence properties of Li2CaGeO4 and Er3+: Li2CaGeO4 crystals

Li2CaGeO4 and Er3+: Li2CaGeO4 crystals were successfully grown by TSSG method. The electronic structure, vacancy defects, near-infrared luminescence, thermodynamic stability, and mechanical properties of the crystals were characterized and analyzed by first principles calculation and experimental tests. The results show that Li2CaGeO4 and Er3+: Li2CaGeO4 crystals are typical wide-gap direct bandgap crystals (3.64 and 3.96 eV). The effect of two cationic vacancy defects on crystal properties was studied. The results show that the defects of O2− or Li+ vacancy leads to the change of band structure, and the coupling degree between conduction band and valence band is reduced, and the degree of hybridization is reduced. The probability of non-radiative transition increases greatly and the luminescence intensity decreases. Spectral tests show that the Er3+: Li2CaGeO4 crystal is an excellent laser crystal with a high near-infrared optical output at 1550 nm (4I13/2 → 4I15/2) and long fluorescence decay lifetime (5.804 ms). The thermal vibration and elastic constants of Er3+: Li2CaGeO4 crystal are calculated by simulation. The results show that Er3+: Li2CaGeO4 crystal is a kind of crystal material with easy processing, good brittleness, good thermal stability, and excellent thermal conductivity. Therefore, it has a very high application prospect in the field of laser or thermoelectric.

Highly Luminescent and Stable Perovskite Quantum Dots Films for Light‐Emitting Devices and Information Encryption

AbstractThe inherent flexibility and excellent mechanical strength of lead halide perovskite quantum dots (LHP‐QDs) films have attracted much attention in the fields of flexible lighting, displays, non‐planar x‐ray imaging, and wearable optoelectronics. Unfortunately, the complicated synthesis process and poor stability limit its practical applications, hence there is an urgent need to develop a feasible fabrication process for films to attain high device performance. Herein, a molecular level hybridization of bridged polysilsesquioxane (BPSQ) is designed as matrix to harvest both flexibility of organics and stability of inorganics, resulting in improved interfacial compatibility between the CsPbBr3 QDs and the matrix through chemical bond anchoring. The CsPbBr3@3‐aminopropyl‐triethoxysilane (APTES)@BPSQ films showcase bright narrow‐band photoluminescence, with a photoluminescence quantum yield of 61% and a half‐peak full width at half maximum of <17 nm. Notably, these films demonstrate excellent environmental stability, UV resistance, water stability (experiencing only an 18% decrease in luminescence intensity after 168 h of water immersion), and high‐temperature stability (withstanding temperatures up to 500 K). Furthermore, white light‐emitting diodes (WLEDs) and anti‐counterfeiting patterns have been fabricated using CsPbBr3@APTES@BPSQ, highlighting their wide application potential in flexible light‐emitting devices and information encryption.

Effect of Ge Incorporation on Lead‐free Cs‐based Triiodide Sn−Ge Co‐alloy Perovskite Thin Films by Spin Coating

AbstractA new Sn−Ge co‐alloy perovskite that does not contain toxic Pb is attracting attention due to its excellent predicted optoelectronic properties. However, most current research only focuses on compositions with Ge content up to 50 %, resulting in a limited overall understanding on this material system. In this study, CsSn1–xGexI3 (0≤x≤1) perovskite thin films were fabricated using spin coating method and characterized in terms of crystallographic, morphological and optical characteristics systematically. The results show that the Ge incorporation causes lattice shrinkage and a change in the crystallographic phase from orthorhombic to trigonal. Additionally, the coverage varies much as Ge increases. The Ge incorporation also results in a blueshift of the photoluminescence peak and a decrease in luminescence intensity as compared to the composition with lower Ge content. Moreover, the carrier dynamics measurement shows that the Ge incorporation increases the carrier nonradiative recombination. This work provides important hints for the development of the Sn−Ge alloy‐based perovskite solar cell.

Broadband near-infrared (NIR) emitting Cr3+ -doped La3 Ga5 SnO14 phosphor with long persistent and photostimulated persistent luminescence.

Recently, long persistent phosphors (LPPs) have attracted significant attention as promising candidates for biomedical applications. However, the serious decrease in luminescence intensity in tissue still remains a major challenge. Therefore, exploring more competitive LPPs and achieving reproducible tissue imaging is crucial. In this study, a new series of near-infrared (NIR) phosphors La3 Ga5 Sn1-x O14 :xCr3+ (x = 0.005-0.05) were synthesized using a high-temperature solid-state method. The as-synthesized samples were characterized using X-ray diffraction, diffuse/photoluminescence spectroscopy, fluorescence decay curves, and thermoluminescence spectroscopy. Upon excitation with ultraviolet light, strong emission bands were observed in the range 600-1200 nm with an optimal doping concentration of x = 0.02mol. Moreover, La3 Ga5 SnO14 :Cr3+ exhibits persistent luminescence due to the presence of suitable energy traps, which prompted the phosphor to emit NIR light even after the removal of the excitation source.

Characterizations of pure and eu-doped ZnO aerogels nanostructures elaborated by a modified sol gel process

Herein we report on the structural and optical properties of pure and Eu-doped (3% at.) ZnO aerogels nanostructures (ZnO-ans) synthesized by sol-gel associated with drying at supercritical conditions of isopropanol (254 °C, 54 bars). The samples were investigated using X-ray diffraction (XRD), SEM, UV-visible spectroscopy, FTIR and photoluminescence (PL). XRD studies exhibit the formation of a high crystal quality ZnO wurtzite hexagonal structure. The UV-visible measurements point out that the absorption intensity and the band gap energy increase after Eu-doping. FTIR analysis confirms the formation of ZnO phase and reveals a shift toward longer wavenumber of the Zn-O absorption band after Eu -doping. SEM images show that Eu3+ ions lead to change the morphology of ZnO crystalline from pastille to sphere. PL measurements reveal a decrease of UV luminescence intensity and an increase of the visible one due to Eu-doping.

UV/ visible/ NIR sensitized enhanced green luminescence of a newly synthesized salicylic acid coated Tb3+ and Yb3+ ions doped Y2O3 nano-composite phosphor: Prospect as luminescence solar collector material

The present work describes the enhancement of green luminescence of Tb3+ ion in a newly synthesized composite material that contains Tb3+ and Yb3+ ions in Y2O3 nano-phosphor (TYY) coated with salicylic acid (SA) doped polyvinyl alcohol (PVA) polymer matrix (TYY: SA/PVA). XRD results reflect nearly 50 nm size of crystallite in TYY phosphor. On coating, the same with SA-doped PVA polymer visualizes the actual particulate size in microns due to aggregation of nano-crystallites of TYY and indicates the formation of organic/inorganic composite material. In down-conversion of UV radiation, both singlet and triplet states of excited state intra-molecular proton transfer species of SA in TYY: SA/PVA composite material transfer their UV (200 nm–370 nm) excitation energy through Fӧrster and Dexter mechanism to 5D4 state of Tb3+ ions, which enhances green luminescence of Tb3+ ions [5D4 →7F5] by nineteen-fold and decrease in the NIR luminescence intensity of Yb3+ ion [2F5/2 → 2F7/2] in TYY/SA/PVA as compared to the TYY sample indicates coating of SA/PVA polymer on the nano phosphor blocks the quantum cutting process from 4f75 d1 excited state of Tb3+ ions to 2F5/2 state of Yb3+ ions. In contrast, TYY: SA/PVA and TYY material exhibit intense green luminescent emission of Tb3+ ions by up-conversion of NIR radiation through a cooperative energy transfer between two Yb3+ ions [2F5/2 → 5D4 excitation]. A thin layer coating of composite phosphor material shows enhancement in the external quantum efficiency of the solar cell by increasing the efficiency of ∼3–5 % in the 400 nm–1000 nm range compared to the bare solar cell. I–V characteristics of the composite show that simultaneous excitation of this composite material with UV/Visible/NIR radiation increases the photon density in blue, green, and NIR regions for reabsorption by the photovoltaic cell. This preliminary study signifies the scope for developing brighter, high photon flux luminescent composite luminescent solar collecter material with low cost.

On the role of Gd3+ ions in enhancement of UV emission from Yb3+–Tm3+ up-converting LiYF4 nanocrystals

Materials capable of emitting ultraviolet (UV) radiation are sought for applications ranging from theranostics or photodynamic therapy to specific photocatalysis. The nanometer size of these materials, as well as excitation with near-infrared (NIR) light, is essential for many applications. Tetragonal tetrafluoride LiY(Gd)F4 nanocrystalline host for up-converting Tm3+–Yb3+ activator-sensitizer pair is a promising candidate to achieve UV–vis up-converted radiation under NIR excitation, important for numerous photo-chemical and bio-medical applications. Here, we provide insights into the structure, morphology, size and optical properties of up-converting LiYF4:25%Yb3+0.5%Tm3+ colloidal nanocrystals, where 1, 5, 10, 20, 30 and 40% of Y3+ ions were substituted with Gd3+ ions. Low gadolinium dopant concentrations modify the size and up-conversion luminescence, while the Gd3+ doping that is exceeding the structure resistance limit of the tetragonal LiYF4 results in appearance of foreign phase and significant decrease of luminescence intensity. The intensity and kinetic behavior of Gd3+ up-converted UV emission are also analyzed for various gadolinium ions concentrations. The obtained results form a background for further optimized materials and applications based on LiYF4 nanocrystals.

Twisted Intramolecular Charge Transfer‐Based Fluorometric Detection of D‐fructose by Boronic Acid‐Containing BF2‐β‐Diketonate Complexes

AbstractNovel BF2‐β‐diketonate complexes 1–4 bearing phenylboronic acid moieties and methoxyphenyl or dimethylaminophenyl groups were synthesized and their photophysical properties, pH response, and reactivity to D‐fructose were evaluated. Complexes 1 and 2 bearing a methoxyphenyl group luminesced with high intensity in a range of non‐polar to polar solvents, except in DMSO, whereas complexes 3 and 4 containing a dimethylaminophenyl group with twisted intramolecular charge transfer (TICT) properties showed a dramatic decrease in luminescence intensity with increasing solvent polarity. The luminescence intensity of complexes 1 and 2 decreased with increasing pH due to intermolecular vibration which associated with hydrogen bonding between the complexes and solvent water molecules, whereas it increased when they reacted with D‐fructose due to the suppression of the intermolecular vibration. In contrast, the luminescence intensity of complexes 3 and 4 increased with increasing pH and upon reaction with D‐fructose due to the loss of its TICT properties. The photophysical properties of complexes 1–4 and the TICT properties of complexes 3 and 4 were supported by density functional theory calculations.

Luminescence and Light-Resistance Features of Mixed Europium–Gadolinium Complexes in Polymer Films

The effect of gadolinium on the luminescence of europium in mixed complexes with thenoyltrifluoroacetylacetone and 1,10-phenanthroline in poly(methyl methacrylate) and polyethylene films has been studied. The scale of change in light resistance with varying the proportion of gadolinium and the concentration of the complex in the polymer has been estimated. An increase in the relative intensity of luminescence in polyethylene with an increase in the proportion of gadolinium in the complexes has been revealed, themagnitude of which corresponds to a similar effect for complexes in the crystalline state. This effect is absent in poly(methyl methacrylate) films; however, the presence of gadolinium lowers the rate of decrease in luminescence intensity during photolysis.

Novel Red-Emitting BaBi2B4O10:Eu3+ Phosphors: Synthesis, Crystal Structure and Luminescence

The novel red-emitting BaBi2−xEuxB4O10 (x = 0.05, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6) phosphors were obtained by a crystallization from a glass. Distribution of the Eu3+ ions over cation sites were refined for x = 0.1, 0.3 and 0.4 from single-crystal X-ray diffraction data. Emission and excitation spectra of the Eu3+-doped BaBi2B4O10 phosphors were investigated for the first time, where it was shown that characteristic lines are attributed to the intraconfigurational 4f-4f transitions. The optimal concentration for the BaBi2−xEuxB4O10 phosphors is x = 0.4, after which a luminescence intensity decreases. The CIE chromaticity coordinates for the BaBi2B4O10:Eu3+ (x = 0.4) phosphor (0.65, 0.35) are close to the NTSC standard values (0.67, 0.33) for commercial red phosphor. The obtained results show that the BaBi2B4O10:Eu3+ phosphors are promising candidates for solid state lighting application.

The roles of dopant concentration and defect states in the optical properties of Sr2MgSi2O7:Eu2+, Dy3+

The blue-emitting Sr2MgSi2O7:Eu2+,Dy3+ was prepared by sol-gel method. The effects of dopant concentration on crystal structure, photoluminescence and afterglow properties were studied. Based on First-principles calculations, the formation difficulty and electronic structures of intrinsic defects and the external defects caused by doping Eu, Dy were predicted, and the defect-dominated persistent luminescence mechanism was proposed. The results showed that when the content of Eu2+ reached 0.03 mol%, Sr2MgSi2O7:Eu2+,Dy3+ had the best luminescence performance. After exceeding this content, the concentration quenching caused by electric dipole-dipole interaction would occur, leading to a decrease in luminescence intensity. The oxygen vacancy as an intrinsic defect was more easily formed in Sr2MgSi2O7. The impurity levels in the forbidden band, which were introduced by oxygen vacancies and Dy doping defects, can effectively capture and release Eu electrons. It is beneficial to prolong the afterglow duration of Eu 4f65d1→Eu 4f7. This work reveals the electron transition and capture paths in the luminescence of Sr2MgSi2O7:Eu2+,Dy3+, which has reference significance for designing defect structures and optimizing optical properties.

Competitive ELISA based on pH-responsive persistent luminescence nanoparticles for autofluorescence-free biosensor determination of ochratoxin A in cereals.

An accurate and sensitive competitive enzyme-linked immunosorbent assay (ELISA) based on persistent luminescence nanoparticles Zn2GeO4:Mn2+, Eu3+ (ZGME) was developed for detecting ochratoxin A (OTA), a powerfully toxic mycotoxin usually found in grains. As a signal output element of autofluorescence-free biosensors, ZGME can be integrated into ELISA with glucose oxidase (GOx)-binding OTA molecules due to its excellent pH-responsive persistent luminescence. In the absence of OTA, the OTA-GOx conjugate was captured by the anti-OTA monoclonal antibody (anti-OTA mAb) pre-coated on the 96-well plate. The results indicate a decrease in the pH value of the solution, which triggered the quenching of ZGME luminescence due to GOx-dependent gluconic acid production. The presence of OTA inhibited the binding of OTA-GOx on the plate, thus decreasing the production of gluconic acid and increasing the persistent luminous intensity of ZGME. Under the optimized concentrations of anti-OTA mAb and OTA-GOx, quantitative determination of OTA was achieved by plotting the increase or decrease in persistent luminescence intensity of ZGME at 535nm. In this study, the linear range was from 0.1μg L-1 to 63μg L-1, and the limit of detection (LOD) was as low as 0.045μg L-1. In five food samples (corn grit, brown rice, soybean, rice, and wheat), the results exhibited good stability and repeatability, with a recovery range from 81.3% to 94.4% and a relative standard deviation (RSD) of less than 4.2%. Hence, the established method provides a sensitive, accurate, and autofluorescence-free approach for the determination of OTA in different grain samples.

LUMINESCENT PROPERTIES OF MILK OF DIFFERENT FAT CONTENT DURING SOURING

The use of optical spectral methods can help in solving problems that arise during the processing of milk and dairy products. Traditional analytical methods (for example, physico-chemical measurements, sensory analysis, chromatography) are relatively expensive, time-consuming and require chemicals and sophisticated analytical equipment, as well as qualified personnel. There is a need to develop faster and less costly ways to monitor changes in the quality of milk and other dairy products during processing and storage. Many non-destructive and non-invasive instrumental methods are available for embedded and online monitoring of food products. These include fluorescence spectroscopy, reflective spectroscopy of the middle and near infrared range, nuclear magnetic resonance, and so on. (Research purpose) The research purpose is studying the photoluminescent characteristics and parameters of milk of various fat content during its souring. (Materials and methods) Measurements of the spectral characteristics of milk excitation in the range of 200-500 nanometers were performed on the Fluorat-02-Panorama spectrofluorimeter. (Results and discussion) An increase in luminescence intensity was noted at an excitation wavelength of 442 nanometers and its decrease at 262 nanometers after a given period of time for a fat content of 3.2 percent. It was determined that for a fat content of 1.5 percent at an excitation wavelength of 262 nanometers, the trend persists, but at an excitation wavelength of 442 nanometers, on the contrary, the luminescence intensity decreases, which requires clarifying experiments. (Conclusions) The obtained results indicate the dependence of milk souring and changes in luminescence intensity over time. It was stated that this observation can be the basis for further research in the field of quality control of dairy products by non-destructive testing based on optical methods.

Orange‐emitting MgO–(Sr,Ba)3SiO5:Eu composite phosphor ceramics for turn signals and warm white laser lighting

AbstractThe research and development of orange‐emitting phosphor ceramics with excellent performance are significant for improving the optical quality of laser lighting and developing‐related emerging applications. For the first time, we prepared an orange‐emitting MgO–(Sr,Ba)3SiO5:Eu composite phosphor ceramic with high thermal conductivity, high thermal stability, and excellent luminescence properties. The thermal conductivity of the phosphor ceramic is as high as 32 W/(m K), and the luminescence intensity decreases by only 20% at 200°C, both of which are better than other orange‐emitting phosphor ceramics reported so far. The luminous efficacy of the phosphor ceramic (41.6 lm/W) is also close to the highest value of orange‐emitting phosphor ceramics until now. In addition, we also explored the application prospects of the composite phosphor ceramics in automotive turn signals and warm white laser lighting. This work provides inspiration for the preparation of other excellent orange‐emitting phosphor ceramics in the future.

Structural and luminescent behaviour of Dy(III) activated Gd3Al5O12 nanophosphors for white-LEDs applications

Single-phased cool white light emissive Gd3-xAl5O12:xDy3+ (x = 0.01–0.07) nanophosphors have been prepared via gel-combustion method. Diffraction data and Rietveld results have affirmed the development of a single cubic phase of all the prepared samples with space group Ia-3d (230). Furthermore, the crystallite size was calculated through Debye-Scherrer's formula and the Williamson-Hall method. In the EDX spectrum, the nonappearance of peaks analogous to the foreign elements affirms the pure synthesis of the considered phosphors. TEM observation reveals agglomerated porous crystalline material with non-uniform shapes and varying particle size in 20–80 nm range. Fourier Transform Infrared (FTIR) spectroscopy has been applied for the examination of chemical bonding with other vibrational characteristics. The luminescence study confirms the intense blue and yellow emission of synthesized phosphors at 482 nm and 576 nm respectively owing to 4F9/2→6HJ (J = 15/2, 13/2) transitions. Moreover, the detailed evaluation of the concentration quenching process established that dipole-quadruple interaction is answerable for the decrease in luminescence intensity after optimum dopant ion concentration. The chromatic analyses recommend that emission from the optimized nanophosphors lies in the region of cool white light. The outcomes of the present investigation propose that Gd3Al5O12:Dy3+ phosphors might be a potential candidate for white-LEDs applications.

Rare-Earth-Doped Barium Molybdate Up-Conversion Phosphor with Potential Application in Optical Temperature Sensing.

A BaMoO4:[Er3+]/[Yb3+] up-conversion (UC) phosphor was synthesized by co-precipitation and calcination of the precursor at 800 °C. The main peak (112) for the synthesized phosphor was strongly detected in the XRD pattern and had a tetragonal structure. The doping of rare-earth ions affected the crystal lattice by shifting the main peak, decreasing the lattice constant, and shifting the position of the Raman signal. The synthesized upconverted phosphor exhibited strong green signals at 530 and 553 nm and weak red signals at 657 nm when excited at 980 nm. The green light emission intensity of the UC phosphor increased as the pump power of the laser increased due to the two-photon effect. The synthesized upconverted phosphor was prepared as a pellet and flexible composite. Thermal quenching led to a decrease in luminescence intensity as the temperature increased, which means that the phosphor can be applied to optical temperature sensing.

Pre-diagnosis of Failure Spots in Orange AlInGaP Light-Emitting Diodes Soaked in Liquid Nitrogen Using Machine Vision and Multiple Optical, Electrical, and Material Characterizations

In this study, Pre-diagnosis of degraded aluminum indium gallium phosphide (AlInGaP) light-emitting diodes (LEDs) that were soaked in liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) was performed. To visualize the early deterioration of LED emission, a combination of material, electrical, optical, and computer-aided machine-vision analysis of LED failure spots on the surface was examined. Results indicate that several small failure spots, which can be identified by the MATLAB processed emission images and surface roughness variation, can be found. Furthermore, LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> soaking induced some local damages inside the device that penetrate the multiple-quantum well. The decrease of current and luminescence intensity also reflects the gradual degradation of the device after being soaked in LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . This integrated analysis and Pre-diagnosis of the degraded device provided early screening of LED failure spots and real-time inspection during operations.