Ultraviolet Light-emitting Diodes Research Articles

High Efficiency Deep Ultraviolet Light-Emitting Diodes With Polarity Inversion of Hole Injection Layer

In this work, we investigate the performance improvement of N-polar AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) by the inversion of the hole injection layer from N-polar to Ga-polar. The influence of different inversion points on the performance and the energy band of DUV LED is systematically studied, and the principle of performance improvement of DUV LED is explained in detail through the analysis of the energy band. Furthermore, according to the simulation results and practical application, an appropriate inversion point is selected. Under the current of 120 mA, with polarity inversion of the hole injection layer, the light output power of the DUV LEDs increases from 21.34 mW to 29.71 mW, and the applied voltage reduces from 16.06 V to 9.63 V. The DUV LED with polarity inversion has a 132% increase in wall-plug efficiency (WPE) compared with the DUV LED which is totally along [000-1] direction. Therefore, polarity inversion is an effective way to achieve high-performance UV-LEDs.

Improving Light Extraction Efficiency of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Combining Thinning p-AlGaN/p-GaN Layer With Ni/Au/Al High-Reflectivity Electrodes

Improving light extraction efficiency (LEE) of AlGaN-based deep-ultraviolet (DUV) light emitting diodes (LEDs) has been attempted by thinning the p-AlGaN/p-GaN layer and adopting Ni/Au/Al composite electrodes. It is found that the thin p-AlGaN/p-GaN layer can reduce the light absorption and the Ni/Au/Al electrodes achieve high reflectivity and Ohmic contact to ensure the enhancement of the light extraction and maintain fine electrical properties. By this approach, the maximum external quantum efficiency of the DUV-LEDs with optimized Ni/Au/Al reflective electrodes is increased by 40%, compared to that with conventional Ni/Au electrodes over the whole current range.

Ultra-narrow-band luminescence with spectral width down to 32 nm in bismuth-activated phosphate phosphors with superior thermal stability

Bismuth-activated phosphors have become popular as a replacement for phosphors based on intensively studied lanthanide ions because of their low spectral reabsorption and sustainable utilization. However, it is of a great challenge to yield narrow-band emission from Bi3+ since its ns2-nsp electron transition lacks the shielding of outer electron orbitals. Herein, we report a new ultra-narrow band Bi3+-activated blue-violet phosphor Ca6BaP4O17 (Ca6BaP4O17:Bi3+). Impressively, its emission band width is down to ∼32 nm, which is less than that of all the reported Bi3+-activated ones. Experimental and theoretical calculation results corroborate that such unusual narrow-band emission originates from Bi3+ ions occupying two cation sites, Ca1 and Ca2, in the Ca6BaP4O17 compound. At 423 K, Ca6BaP4O17:0.5%Bi3+ shows a robust thermal quenching resistance with an integrated emission intensity loss of merely 1%. This is attributable to rare structural advantages of the host such as a high Debye temperature (Θ = 632 K) and large bandgap (∼6.1 eV), which could minimize thermally non-radiative relaxation pathways. We fabricate a blue-violet LED prototype by using the resulting phosphors and ultraviolet LED chip, and demonstrate its potential application in porrets growth. These findings provide in-depth insights the on site occupancy of Bi3+ ions and may simulate more research studies on Bi3+-activated phosphors.

Conventional and Inverted Light-Emitting Diodes with 386 nm Emission Wavelength Based on Metal-Free Carbon Dots

Ultraviolet (UV) light-emitting diodes (LEDs) are of great concern due to wide applications in the fields of solid-state displays, photocommunication, and scientific and medical instruments. During the past 10 years, organic and inorganic semiconductors have made great breakthroughs in short-wavelength emission. Nowadays, carbon dots (CDs), which possess distinctive superiorities of high stability, nontoxicity, and low cost, are promising all-band emission materials for the next generation of LEDs. However, the fabrication of CD-based LEDs (CD-LEDs) with emission wavelengths below 400 nm is still a huge limitation in this field. Herein, we prepared UV emission CDs with the photoluminescence emission wavelength of 371 nm. The UV-CDs are perfectly compatible with both conventional and inverted device structures so as to realize the currently shortest electroluminescent emission wavelength of 386 nm for CD-LEDs. The conventional UV-CD-LEDs possess the optimum luminance of 268 cd m-2 (5427 W sr-1 m-2) with an external quantum efficiency (EQE) of 1.115%. Meanwhile, the inverted UV-CD-LEDs possess the optimum luminance of 132 cd m-2 (2673 W sr-1 m-2) with an EQE of 0.869%. This work paves a new road to manufacture carbon nanomaterial-based UV emission devices with high luminance, EQE, and stability.

Insight into micropollutant abatement during ultraviolet light-emitting diode combined electrochemical process: Reaction mechanism, contributions of reactive species and degradation routes

Electrochemical process coupling with ultraviolet light-emitting diode for micropollutant abatement was evaluated in the treatment of wastewater containing Cl−. Four representative micropollutants, atrazine, primidone, ibuprofen and carbamazepine, were selected as target compounds. The impacts of operating conditions and water matrix on micropollutant degradation were investigated. Fluorescence excitation-emission matrix spectroscopy spectra and high performance size exclusion chromatography were employed to characterize the transformation of effluent organic matter in treatment. The degradation efficiencies of atrazine, primidone, ibuprofen and carbamazepine are 83.6 %, 80.6 %, 68.7 % and 99.8 % after 15 min treatment, respectively. The increment of current, Cl− concentration and ultraviolet irradiance promote the micropollutant degradation. However, the presence of bicarbonate and humic acid inhibit micropollutant degradation. The mechanism of micropollutant abatement was elaborated based on reactive species contributions, density functional theory calculation and degradation routes. Free radicals (HO•, Cl•, ClO• and Cl2•-) could be generated by chlorine photolysis and subsequent propagation reactions. The concentrations of HO• and Cl• are 1.14 × 10−13 M and 2.0 × 10−14 M in optimal condition, respectively, and the total contributions of HO• and Cl• for the degradation of atrazine, primidone, ibuprofen and carbamazepine are 24 %, 48 %, 70 % and 43 %, respectively. The degradation routes of four micropollutants are elucidated based on intermediate identification, Fukui function and frontier orbital theory. Micropollutants can be effectively degraded in actual wastewater effluent, and the small molecule compound proportion increases during effluent organic matter evolution. Compared with photolysis and electrolysis, the coupling of the two processes has potential for energy saving in micropollutant degradation, which shed light on the prospects of ultraviolet light-emitting diode coupling with electrochemical process for effluent treatment.

The optical properties behavior of modify poly(methyl methacrylate) nanocomposite thin films during solar energy absorption

Herein, nanoparticles (Co3O4, Cr2O3, CuO, and TiO2) doped PMMA were fabricated via casting method. The PMMA nanocomposite thin films have been prepared with a fixed concentration of 4 g from PMMA to make PMMA thin films, they were modified with amine cluster. These thin films were doped by a fixed concentration, 0.01 gm, of various nanomaterials (Co3O4, Cr2O3, CuO, and TiO2) to make the nanocomposite thin films of PMMA. The thin film samples were examined by UV–Visible wavelength between (250–1350 nm). The optical properties, optoelectronic features, and oscillator strength were investigated. The reflectance and transmittance values were decreased for all the nanocomposite thin films of PMMA. The absorption coefficient ranged between (99.8–92.0%) for all samples. The direct energy gap decreased from 4.65 eV for the blank PMMA and it with Co3O4 to 2.10 eV, also, for the indirect energy gap decreased from 4.2 eV for the blank PMMA and it with Co3O4 to 2.8 eV due to the modified and doped PMMA. The optoelectronic features such as dielectric of high frequency and effective mass increased, oscillator strength decreased, dispersion energy and effective energy of single oscillator increased in comparison to blank PMMA. The oscillator strength for these thin films were increased also. These nanocomposite thin films are suitable to enhance the photostability performance from UV light and drastic weather are needed especially for underwater, aerospace, and applications for air transport, in addition, fabricated shields from UV energy, light-emitting diodes, lasers sensors, memory devices, harvesting light, and converting-light devices.

High-Quality AlN Grown on Si(111) Substrate by Epitaxial Lateral Overgrowth

We report on the epitaxial lateral overgrowth (ELO) of high-quality AlN on stripe-patterned Si(111) substrates with various trench widths. By narrowing down the trench and ridge widths of patterned Si substrates, crack-free, 6-micrometer-thick, high-quality AlN films on Si substrates were produced. The full-width-at-half-maximum values of the X-ray-diffraction rocking curves for the AlN (0002) and (101¯2) planes were as low as 260 and 374 arcsec, respectively, corresponding to a record low dislocation density of 1.3 × 109 cm−2. Through the combination of a micro-Raman study and the X-ray diffraction analysis, it was found that narrowing the stripe width from 5 μm to 3 μm can reduce the vertical growth thickness before coalescence, resulting in a large decrease in the internal tensile stress and tilt angle, and, therefore, better suppression in the cracks and dislocations of the ELO–AlN. This work paves the way for the fabrication of high-performance Al(Ga)N-based thin-film devices such as ultraviolet light-emitting diodes and AlN bulk acoustic resonators grown on Si.

Photoluminescence Behaviors in Self-Assembly Supramolecular Pyridinium Salts

The host–guest supramolecular organic salts would be of great interest due to their excellent optical and electronic properties. Herein, we report three supramolecular materials, o-2MAP, m-3MAP, and p-4MAP, composed of 18-crown-6 and pyridine amine salts, which are crystallized in space groups P1̅, P1̅, and P21/n with a pendulum-like structural variation at room temperature. They all show blue photoluminescence with photoluminescence quantum yields (PLQYs) of 26.85, 77.08, and 32.67%, respectively. The experimental and theoretical analyses reveal that PL emission is associated with strong π–π * and n–π* absorption and charge transition, while hydrogen bond nonvalent interactions affect their structures and cause the enhancement of PLQY. Especially, deep-blue PL materials m-3MAP with the highest PLQY have been used as excellent color conversion media to fabricate ultraviolet light-emitting diodes (UV-LEDs) and anticounterfeiting inks for handwriting and transfer-printing. This work caters to a reliable strategy to design novel optical supramolecular materials and extends their applications for PL materials.

Performance of UV-LED and UV-C treatments for the inactivation of Escherichia coli ATCC 25922 in food model solutions: Influence of optical and physical sample characteristics

Shortwave ultraviolet light (UV-C) and ultraviolet light-emitting diodes (UV-LEDs) are emergent technologies to inactivate pathogenic and spoilage microorganisms in food. However, the effectiveness of these technologies is influenced by the optical properties of the treated food. This work aimed to evaluate the effect of the optical properties of nine model food solutions on the efficacy of UV-C (at 255 nm) and UV-LEDs (at 255, 265 or 280 nm) to inactivate E. coli ATCC 25922. Model solutions were formulated with saccharose (SC), tartrazine (TT) and xanthan gum (XG), exposed from 0 to 50 min. The microbial population was reduced after 15 min of UV-C and UV-LED treatment by >6 log CFU/mL for water and TT, and by UV-C for SC, XG, TT + SC, and (XG + TT + SC) m solutions. The inactivation data were correlated using three different models. Colored compound (TT) showed 60% degradation by UV-C compared to 3% by UV-LED at 50 min. Industrial relevanceNon-thermal treatments such as those based on ultraviolet light, UV-C, and UV-LEDs could have high industrial relevance because of their simplicity of operation and reduced by-product formation, being a friendly alternative for food processing. Understanding the effect of different optical and physicochemical properties of liquid food to be treated by UV-based technologies is mandatory for the equipment's efficient design and operation. Furthermore, the proper selection of processing conditions, such as delivered dose and processing time, allows for obtaining safe and high-quality products.

Quantum Efficiency Improvement of InGaN Near Ultraviolet LED Design by Genetic Algorithm

A near-ultraviolet (367-nm) InGaN light-emitting diode (LED) with 5.75 nm quantum well depth was designed and both internal/external quantum efficiency (IQE/EQE) values were optimized considering the effects of non-radiative recombination rates and possible fabrica-tion errors. Firstly, the IQE of the design was enhanced by a genetic algorithm code which was developed particularly for this study. Distributed Bragg Reflectors and optional ultra-thin 1nm AlN interlayer were also used to increase overall light extraction efficiency. Then, alloy and doping concentration effects on wavelength-dependent optical and structural parameters were analyzed via the CASTEP software package based on density functional theory to pre-sent a more detailed and realistic optimization. The relatively great values of 42.6% IQE and 90.2% LEE were achieved. The final structure with 1.00 mm × 1.00 mm surface area requires only 200 mW input power to operate at 3.75 V.

Investigation of V/III ratio dependencies for optimizing AlN growth during reduced parasitic reaction in metalorganic vapor phase epitaxy

AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) are expected to have various applications, including sensing and printing, and light with ultraviolet-C (UVC) wavelengths has a virus inactivation effect. The metalorganic vapor phase epitaxy (MOVPE) method has been used to fabricate LED devices with film control and impurity doping. However, to achieve high luminous efficiency, highly crystalline aluminum nitride (AlN) must be grown in the underlying layer. Although high temperatures are required to grow high-quality AlN for strong migration at the surface, there is a trade-off in the high temperature promoting parasitic reactions. These parasitic reactions are more dominant at a high V/III ratio with more raw material in the case of using the conventional MOVPE. Here, we used jet stream gas flow MOVPE to investigate the effect of V/III ratio dependencies in optimizing AlN growth and without affecting parasitic reaction conditions. As a result, trends of typical AlN crystal growth at V/III-ratio dependencies were obtained. AlN is more stable at a higher V/III ratio of 1000, exhibiting a double atomic step surface, and the crystal orientation is further improved at 1700 °C compared to that at a lower V/III ratio.

Design and demonstration of efficient transparent 30% Al-content AlGaN interband tunnel junctions

Ultra-violet (UV) light emitting diodes operating at 339 nm using transparent interband tunnel junctions are reported. Tunneling-based ultraviolet light emitting diodes were grown by plasma-assisted molecular beam epitaxy on 30% Al-content AlGaN layers. A low tunnel junction voltage drop is obtained through the use of compositionally graded n and p-type layers in the tunnel junction, which enhance hole density and tunneling rates. The transparent tunnel junction-based UV LED reported here show a low voltage drop of 5.55 V at 20 A/cm2 and an on-wafer external quantum efficiency of 1.02% at 80 A/cm2.

Aggregation-Induced White Light Emission and Solvent-Induced Dual Mode Multi-Analyte Sensing by Highly Crystalline Single Component Derived N, S Co-Doped Carbon Nanodots

Recently, carbon nanodots (CNDs), the zero-dimensional carbon nanomaterials, have attracted immense research interest. Besides inherent traits like biocompatibility, eco-friendliness, electron mobility, and water-soluble nature, CNDs, as a green material with inherent luminescence, have grabbed a lot of attention and have opened up applications in more real-world contexts. In the present study, we project methionine-derived N, S co-doped CNDs as an efficient candidate for white-light-emitting diode (WLED) applications and dual-mode multianalyte sensing, based on their covetable fluorescence. Here, a scalable, dry white-light-emitting solid material is achieved from the aqueous dispersion of CNDs through freeze-drying process, without encountering the usual hurdles that are met with in solid-state CND systems, such as aggregation-caused quenching (ACQ) in luminescence, incomplete dryness, and low yield. The present system stands distinct, as warm white light is achieved by simply integrating the white light emitting single-component derived CND powder with near ultraviolet LED chips (370 nm) without ACQ resistors or additional phosphors. WLEDs with a low correlated color temperature of 3762 K and a moderately high color rendering index, which are suitable for interior lighting, are achieved. Along with the optoelectronic application, the system is potent enough to respond to the presence of two biologically significant species, folic acid and Fe3+ ions, through a dual-mode operation, viz, fluorescence turn-on and turn-off strategies, respectively. Excellent selectivity from a galaxy of 34 analytes is noted for the system, with attractive detection limits of 0.709 and 14.08 μM for folic acid and ferric ion, in the respective order. A detailed investigation of the mechanisms proves the inner filter effect (IFE) and Forster resonance energy transfer-mediated fluorescence enhancement and IFE-mediated quenching effect, operating here.

High growth temperature for AlN by jet stream gas flow metalorganic vapor phase epitaxy

Deep ultraviolet light-emitting diodes have attracted considerable attention for realizing virus inactivation applications. The UV-LEDs use the AlN underlying layer and the plane sapphire substrate. However, the low growth temperature in AlN underlying layer is grown by limited growth temperature in conventional MOVPE, and high temperature is preferable for AlN growth. Furthermore, the AlN underlying layer has many dislocations owing to the active layer in the device region when the flat sapphire substrate was used with a dislocation value of > 109 cm−2. We showed the high-temperature crystal growth of AlN with a temperature of 1700 °C by high temperature and gas flow velocity MOVPE. The achieved dislocation density was ~ 4 × 108 cm−2. Additionally, this data means the low dislocation densities in the AlN layer with a growth time of only 15 min and a dislocation density of < 1 × 109 cm−2 are obtained. The AlN growth temperature exceeding 1550 °C decreases the growth rate. These results indicate desorption from the surface of the substrate in a hydrogen atmosphere. Furthermore, the characteristic dislocation behavior of AlN in high-temperature growth at 1700 °C was elucidated from TEM images.

Review of Recent Advances of GaN Nanostructured Based Devices

This paper is intended to provide an overview of recent advances of GaN based nanostructured materials and devices. Because of its unique electrical, optical, and structural properties, GaN has sparked significant interest in the field of wide bandgap semiconductor research. Because of its higher surface-to-volume ratio than thin films, GaN nanostructured material offers numerous advantages for nanodevices. The ability of GaN nanostructured material to absorb ultraviolet (UV) radiation is invaluable in many optical applications. GaN nanostructured-based devices have recently received a lot of interest due to their numerous potential uses. GaN has been employed as a nanomaterial in a variety of devices, including UV photodetectors, light-emitting diodes, solar cells, and transistors. The most current developments in GaN-based devices are presented and reviewed. The performance of many device architectures demonstrated on GaN is presented. The structural, electrical, and optical characteristics are also discussed.

Core-Shell Nanorods as Ultraviolet Light-Emitting Diodes.

Existing barriers to efficient deep ultraviolet (UV) light-emitting diodes (LEDs) may be reduced or overcome by moving away from conventional planar growth and toward three-dimensional nanostructuring. Nanorods have the potential for enhanced doping, reduced dislocation densities, improved light extraction efficiency, and quantum wells free from the quantum-confined Stark effect. Here, we demonstrate a hybrid top-down/bottom-up approach to creating highly uniform AlGaN core-shell nanorods on sapphire repeatable on wafer scales. Our GaN-free design avoids self-absorption of the quantum well emission while preserving electrical functionality. The effective junctions formed by doping of both the n-type cores and p-type caps were studied using nanoprobing experiments, where we find low turn-on voltages, strongly rectifying behaviors and significant electron-beam-induced currents. Time-resolved cathodoluminescence measurements find short carrier liftetimes consistent with reduced polarization fields. Our results show nanostructuring to be a promising route to deep-UV-emitting LEDs, achievable using commercially compatible methods.

Inactivation kinetics of 280 nm UV-LEDs against Mycobacterium abscessus in water

Nontuberculous mycobacteria (NTM) are opportunistic premise plumbing pathogens (OPPPs) that cause a burdensome waterborne respiratory disease. Due to their resistance to chemical disinfectants and regrowth in biofilms in drinking water distribution systems, treatment can be better performed using small ultraviolet disinfection units at the point-of-use (POU), such as at a tap or showerhead. Ultraviolet light-emitting diodes (UV-LEDs) are well suited for such applications, but fluence-response data are not available for one of the most important NTM, Mycobacterium abscessus. In this study, a bench-scale 280 nm UV-LED apparatus was used to irradiate M. abscessus in a water matrix. The fluence-response profile was sigmoidal, exhibiting both shoulder and tailing phenomena. Simple linear regression and the Geeraerd’s inactivation kinetics model yielded k values of 0.36 and 0.37 cm2/mJ, respectively, revealing that M. abscessus is more resistant to UV than Pseudomonas aeruginosa and Legionella pneumophila, which suggests that NTM are among the most UV-resistant OPPPs. Results of this study suggest that 280 nm UV-LED irradiation can be an effective and practical option to inactivate M. abscessus at the POU. Disinfection units that can deliver a fluence of 10 mJ/cm2 are expected to achieve nearly 2 log (99%) inactivation of M. abscessus.

Antimicrobial efficacy and inactivation kinetics of a novel LED-based UV-irradiation technology

Ultraviolet (UV)-light-emitting diodes (UV-LEDs) are energy efficient and of special interest for the inactivation of micro-organisms. In the context of the coronavirus disease 2019 pandemic, novel UV technologies can offer a powerful alternative for effective infection prevention and control. This study assessed the antimicrobial efficacy of UV-C LEDs on Escherichia coli, Pseudomonas fluorescens and Listeria innocua, as well as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), human immunodeficiency virus-1 (HIV-1) and murine norovirus (MNV), dried on inanimate surfaces, based on European Standard EN 17272. This study found 90% inactivation rates for the tested bacteria at mean UV-C doses, averaged over all three investigated UV-C wavelengths, of 1.7mJ/cm2 for E.coli, 1.9mJ/cm2 for P.fluorescens and 1.5mJ/cm2 for L.innocua. For the tested viruses, UV doses <15mJ/cm2 resulted in 90% inactivation at wavelengths of 255 and 265nm. Exposure of viruses to longer UV wavelengths, such as 275 and 285nm, required much higher doses (up to 120mJ/cm2) for inactivation. Regarding inactivation, non-enveloped MNV required much higher UV doses for all tested wavelengths compared with SARS-CoV-2 or HIV-1. Overall, the results support the use of LEDs emitting at shorter wavelengths of the UV-C spectrum to inactivate bacteria as well as enveloped and non-enveloped viruses by exposure to the appropriate UV dose. However, low availability and excessive production costs of shortwave UV-C LEDs restricts implementation at present, and supports the use of longwave UV-C LEDs in combination with higher irradiation doses.

Wafer-scale high sensitive UV photodetectors based on novel AlGaN/n-GaN/p-GaN heterostructure HEMT

We report a novel high sensitive ultraviolet (UV) photodetector based on AlGaN/n-GaN/p-GaN heterostructure high electron mobility transistor (HEMT) on sapphire substrates and have prepared four types of devices with identical lengths but different widths of the effective region on one wafer. Since the existence of the built-in electric field within p-GaN and n-GaN, the two-dimensional electron gases (2DEGs) at the AlGaN/n-GaN interface is effectively depleted, leading to ultra-low dark current at pA level. Under UV LED irradiation with wavelength of 365 nm, the photodetectors demonstrate extremely high light on/off ratio (Ilight/Idark) of about 106 and high photoresponse speed with the rise time (τrise)/decay time (τdecay) of 1.53 ms/2.21 ms at Vds = -5 V under light power density of 236.97 mW/cm2. Furthermore, the R of the photodetector reaches 9.12 A/W, the EQE and D* are as high as 3100 % and 1.95 × 1013 Jones, respectively, indicating overall high performances of the device in terms of photoresponsivity, EQE, detectivity and robust stability. The proposed photodetectors with merits of p-GaN etchless compared with conventional E-mode p-GaN HEMT and wafer-scale mass production may pave the way for the application of UV communication, Internet of Things and medical treatment.

A novel exposure mode based on UVA-LEDs for bacterial inactivation.

As an emerging UV source, ultraviolet light-emitting diodes (UV-LEDs) are increasingly being used for disinfection purposes. UVA-LEDs have a higher output power, lower cost, and stronger penetration and cause less harm than UVC-LEDs. In this study, a novel exposure mode based on UVA was proposed and well demonstrated by various experiments using S. aureus as an indicator. Compared with single-dose exposure, fractionated exposure with a 15min interval between treatments resulted in increased S. aureus inactivation. A longer interval or lower first irradiation dose was unfavorable for inactivation. Fractionated exposure changed the inactivation rate constant and eliminated the shoulder in the fluence-response curves. This resulted in changing the sensitivity of bacteria to UVA and improving bacterial inactivation. Moreover, the fractioned exposure mode has universality for various bacteria (including gram-positive and gram-negative bacteria). S. aureus was not reactivated by photoreactivation or dark repair after UVA treatment. As expected, the cells were damaged more seriously after fractionated exposure, further suggesting the advantages of this new exposure mode. In addition, the mechanism by which bacteria were inactivated after fractionated exposure was investigated, and it was found that •OH played an important role. A longer interval between treatments showed an adverse effect on inactivation, mainly due to the reduction of •OH and recovery of intracellular GSH. In summary, the current work provides novel ideas for the application of UVA-LEDs, which will give more choices for disinfection treatment.