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Inorganic Printed LEDs for Wearable Technology
摘要： A new form of inorganic printed electronics has been developed that allows for high speed production of solid-state lighting on flexible substrates. Light emitting diodes (LED) become more efficient as their size is decreased. However, the difficulties in making the electrical connection to micro LEDs has previously prevented these benefits being exploited outside the laboratory. Standard InGaN film, grown on a defined substrate (heteroepitaxy), was fabricated into micro LEDs (approx. 27 μm) and dispersed in a carrier fluid to form an ink, which can then be printed using established printing technologies. During printing and curing, the geometry of the individual micro LEDs causes them to orientate into a single preferential direction. Connections can then be made via further printed layers of conductive and dielectric ink to create flexible lamps consisting of areas of discrete LEDs. These lamps have low power consumption and high light output making them ideal for incorporating into garments and for packaging. The “Thunderstorm” dress (a Rainbow Winters project) was developed for the “Wired to Wear” exhibition in the Museum of Science and Industry, Chicago (MSI) to demonstrate the potential of this technology. The concept was to turn the wearer into a living representation of a thunderstorm. The concept had previously been realised in 2010 using electroluminescent elements (EL) to create a lightning flash in the panels of the dress. However, this required the wearer to carry high voltage devices, bulky electronics and heavy batteries. Instead, using inorganic printed LEDs afforded the potential to create a truly wearable piece of haute couture, using low voltages, miniature electronics and small batteries. The work reported here describes the fabrication technique used to create the micro LED lamps and the issues related to their integration into a piece of wearable technology. The lamps could be driven in such a way as to create a more realistic flash compared to the EL version. Other potential applications such as smart packaging, are also discussed.
关键词： wearable technology,inorganic LEDs,printed electronics
更新于2025-09-23 15:21:01
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Dual-mode light-emitting lanthanide metal-organic frameworks with high water and thermal stability and its application in white LEDs
摘要： It is well known that the up-conversion luminescence from lanthanide metal-organic frameworks (Ln-MOFs) is difficult to achieve, and thus, there are few reports on dual luminescence-based MOFs. Here, dual-mode light-emitting Ln-MOFs are synthesized using a low-cost hydrothermal method. Our results show that the obtained Ln-MOFs not only have high thermal stability (up to 420 degrees) but also are stable in deionized water. The dual-mode up and down-conversion luminescence is simultaneously observed from Er-Eu-MOFs. The temperature-dependent fluorescence decay time is calculated to be ranged from 0.46 ms to 0.36 ms for temperatures from100 K to 300 K. We suggested that this phenomenon was because the number of phonons participating in the MOF matrix increases with temperature during the luminescence process, and the phonons interact with the electrons in the material. The values of the J-O parameters calculated from the emission spectra indicated that the symmetry around Eu3+ ions in Eu-MOF is the highest, which was also higher than that of Er-Eu-MOF. To explore the potential applications of Eu-MOFs in white light-emitting diodes (LEDs), red emission from Eu-MOFs was combined with blue, green, and yellow emissions from metal halide perovskites to achieve white light emission. The white light with excellent color quality and vision performance was obtained. These findings demonstrate that the Ln-MOFs are potentially successful materials for the applications in white LEDs.
关键词： high thermal stability,Dual-mode luminescence,LEDs,MOFs,lanthanide
更新于2025-09-23 15:21:01
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A K3ScSi2O7: Eu2+ based phosphor with broad-band NIR emission and robust thermal stability for NIR pc-LEDs
摘要： In this work, an Eu2+-doped K3ScSi2O7 (KSSO) NIR phosphor with broad-band NIR emission and robust thermal stability was designed and synthesized successfully. The crystal structure, luminescent properties, the mechanism of abnormal NIR emission, thermal stability and application to NIR pc-LEDs were investigated in detail.
关键词： NIR phosphor,Eu2+-doped,K3ScSi2O7,thermal stability,NIR pc-LEDs,broad-band emission
更新于2025-09-23 15:21:01
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[IEEE 2020 IEEE Radio and Wireless Symposium (RWS) - San Antonio, TX, USA (2020.1.26-2020.1.29)] 2020 IEEE Radio and Wireless Symposium (RWS) - Optimized LEDs Positions for Channel Analysis Performance of an Intra-Vehicle Visible Light Communication System
摘要： This paper investigates the effect of light emitting diodes (LEDs) positioning and allocation in the channel analysis performance for an indoor intra-vehicle visible light communication (VLC) system. The MATLAB simulation results focus on the received power and the signal to noise ratio (SNR) within a sports utility vehicle. Furthermore, this work aims to validate by investigating two different scenarios, one utilizing two sources of power and the other using three sources of power with various locations, how LED's spatial positioning affects the VLC system and the probability of error. Proving the demand for considering LEDs layout positioning while designing a VLC system.
关键词： SNR,LEDs positioning,Intra-vehicle,Visible light communication (VLC)
更新于2025-09-23 15:21:01
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Testing of Various Monochromatic LED Lights Used in Supplemental Irradiation of Lettuce in Modern Urban Rooftop Polytunnels
摘要： Urban farming could provide both vegetable growers and urban dwellers with more direct access to various fresh vegetables. Nevertheless, certain challenging problems associated with urban farming, including a lack of cultivation space and the effects of urban heat islands, must still be solved. Relatedly, a grower must, in some cases, also know how to utilize various forms of technology, such as lighting systems, as well as factors such as water availability. In this study, an original rooftop polytunnel design for lettuce (Lactuca sativa cv. Lollo Rosso) cultivation equipped with a hydroponic system and light emitting diodes (LEDs) is proposed. Various monochromatic lights were also tested for their effects on different quality parameters of lettuce. Specifically, supplemental red (655 nm), blue (445 nm), green (520 nm), and ultraviolet (380 nm) LED lights were used at night to apply photon fluxes of 150, 150, 150, and 20 μmol·m-2·s-1, respectively. The resulting effects of these different colored LEDs on the pigment concentration and growth response of the lettuce grown inside the roof polytunnel were then investigated. The experiment was then repeated several times with different environmental parameters in order to compare the effects of the different light wavelengths under higher temperatures and higher natural irradiation conditions. The results indicated that supplemental red or blue light at night could be strategically employed to maintain low nitrate levels and enhance the nutritional value and growth of lettuce grown in roof polytunnels.
关键词： Red lettuce,Rooftop polytunnel,Hydroponic,LEDs,Urban agriculture,Light emitting-diodes
更新于2025-09-23 15:21:01
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Mechanisms of LiF Interlayer Enhancements of Perovskite Light-Emitting Diodes
摘要： The use of LiF as a thin interlayer between the electron transport layer and cathode has played a pivotal role in remarkable advances in perovskite LEDs (PeLEDs); however, the mechanism behind the effect of LiF remains to be fully understood. Here we report a combined experimental and computational study from which we ascribe the benefits of a LiF interlayer to the migration of dissociated Li into the cathode and dissociated F into the anode. Electronic device simulations reveal that the former improves electron injection by lowering the Schottky barrier height, while the latter reduces the barrier width. These reduce turn-on voltage and improve current density and charge balance in LEDs. We fabricate PeLEDs with and without the LiF interlayer and link these materials and electronic phenomena to the device light-current-voltage characteristics. X-ray photoelectron spectroscopy obtained in sputter profiling of PeLEDs corroborates the dissociation of LiF.
关键词： LEDs,interface dipoles,metal-halide perovskites,photoelectron spectroscopy,band alignment
更新于2025-09-23 15:21:01
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Substituent Effects on Photoinitiation Ability of Monoaminoanthraquinonea??Based Photoinitiating Systems for Free Radical Photopolymerization under LEDs
摘要： Three monoamino-substituted anthraquinone derivatives (AAQs), that is, 1-aminoanthraquinone (AAQ), 1-(methylamino)anthraquinone (MAAQ), and 1-(benzamido)anthraquinone (BAAQ), incorporated with various additives [e.g., triethanolamine (TEAOH) and phenacyl bromide (PhC(═O)CH2Br)] are investigated for their roles as photoinitiating systems of free radical photopolymerization of (meth)acrylate monomers upon the exposure to UV to green LEDs. The AAQs-based photoinitiating systems, AAQ/TEAOH/PhC(═O)CH2Br and BAAQ/TEAOH/PhC(═O)CH2Br photoinitiators exhibit the highest efficiency for the free radical photopolymerization of DPGDA under the irradiation of blue LED and UV LED, respectively, which is consistent with the extent of overlap between their absorption spectra and the emission spectra of the LEDs. AAQ/TEAOH/PhC(═O)CH2Br photoinitiator can also initiate the free radical photopolymerization of different (meth)acrylate monomers, with an efficiency dependent on the chemical structures of these monomers.
关键词： LEDs,free radical photopolymerization,aminoanthraquinone,photo initiators
更新于2025-09-23 15:21:01
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High brightness blue light-emitting diodes based on CsPb(Cl/Br)3 perovskite QDs with phenethylammonium chloridesynonym passivation.
摘要： All inorganic perovskite quantum dots (QDs) (CsPbX3, X=Cl, Br, I) have been applied on the light-emitting devices (LEDs) in recent years due to their excellent optical and optoelectronic properties. However, the blue-light emitting perovskite QD LEDs (PQD-LEDs) exhibit the poor performances comparing with their green- and red-light emitting counterparts. Herein, we fabricated the high performing blue-light emitting PQD-LEDs based on the phenethylammonium chloridesynonym (PEACl) modified CsPb(Cl/Br)3 QDs. Firstly, the PEA-CsPbCl3 QDs were synthesized by introducing the certain amounts of PEACl in the conventional hot-injection synthesis process. The merit of our synthesis lies in the fact that not only the Cl vacancies of CsPbCl3 QDs are efficiently modified by introducing the PEACl precursor, but also the partial long-chain organic ligands (OLA) capping on the surface of CsPbCl3 QDs are simultaneously replaced by the shorter PEACl chains. Consequently, the PEA-CsPbCl3 QDs emitted at 410 nm with the PLQY of 62.3% was achieved. Furthermore, to meet the requirement of display application, we exchanged Cl- with Br- ions at room temperature to precisely control the blue emission in 460-470 nm spectral regions and with the maximum PLQY of 80.2% at 470 nm. Finally, the PQD-LEDs based on PEA-CsPb(Cl/Br)3 perovskite QDs emitted at 462, 465, 468 and 470 nm were fabricated. The PQD-LEDs exhibit the maximal EQE of 2.15% and luminance of 620 cd/m2, which provides a highest value of luminance for the PQD-LEDs in the blue spectral range that satisfying the practical display application.
关键词： perovskite quantum dots,LEDs,CsPb(Cl/Br)3,blue-light emitting,phenethylammonium chloride
更新于2025-09-23 15:21:01
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Synthesis and photoluminescence properties of high thermal stability Mn4+ in orthorhombic SrLa2Mg2W2O12 red phosphor for warm w-LEDs
摘要： We successfully synthesized SrLa2Mg2W2O12:xMn4+ (x = 0.002, 0.004, 0.006, 0.008, 0.010, 0.012, 0.014) phosphors through a high-temperature solid-state reaction. The phase of sample was shown by X-ray powder diffraction (XRD). The morphology of the sample was observed by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM), which showed the irregular morphology of SrLa2Mg2W2O12 (SLMW) powders. Additionally, the photoluminescence excitation (PLE), emission (PL) and ultraviolet–visible reflection spectra were also presented. As shown in results, the phosphor could be stimulated by the ultraviolet (UV) and near ultraviolet (NUV) light and then exhibited far-red emission (697?nm). The optimum doping concentration of Mn4+ is 1?mol%. The thermal stability of phosphors has been investigated and discussed (I423K/I298K = 64.6%), and the internal quantum efficiency (IQE) of SLMW:0.01Mn4+ phosphors is as high as 51.2%. Finally, a far-red light-emitting diodes (LEDs) was fabricated by combining a 365?nm near-ultraviolet InGaN chip with SLMW:0.01Mn4+ phosphor. The Color Rendering Index (CRI), correlated color temperature (CCT) and luminescent efficiency (LE) values were 29.5, 1159?K and 5.6?lm/W, respectively. All of these indicated that SLMW:Mn4+ as a far-red phosphor can be applied to LEDs lamp and it has enormous potential applications in white light-emitting diodes (w-LEDs).
关键词： SrLa2Mg2W2O12:Mn4+,far-red emission,thermal stability,w-LEDs,phosphor
更新于2025-09-23 15:21:01
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Tunable photoluminescence and energy transfer of novel phosphor Sr9La2W4O24:Sm3+, Eu3+ for near-UV white LEDs
摘要： Novel Sr9La2W4O24:xSm3+ and Sr9La2W4O24:0.15Sm3+, yEu3+ orange-red phosphors with double perovskite tungsten structure are synthesized by high-temperature solid-phase reaction method. X-ray diffraction patterns indicate the prepared phosphors are pure phase with a tetragonal structure and the SEM image displays the long string structure with a diameter of one micron. Under the excitation of near-UV light, the Sm3+ and Eu3+ ions activated Sr9La2W4O24 phosphors exhibit their characteristic emissions in the orange-red region, and the emitting light color of the Sr9La2W4O24:0.15Sm3+, yEu3+ phosphors can be adjusted from orange to red by increasing the concentration of Eu3+ ions implying their potential applications as orange-red emitting phosphor for LED in solid-state lighting. The optimal doping concentration of Sm3+ ions in Sr9La2W4O24:xSm3+ phosphors is around 15?mol%. The energy transfer from Sm3+ to Eu3+ is discussed and the major mechanism for concentration quenching is the dipole–dipole (d–d) interaction.
关键词： Sm3+,phosphors,energy transfer,double perovskite,Eu3+,white LEDs
更新于2025-09-23 15:21:01