Journal articles: 'Light emitting diodes (LEDs)'

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Sreedhar, K. V. S. "Light Emitting Diodes (LEDs)." IOSR Journal of Electronics and Communication Engineering 9, no. 2 (2014): 07–13. http://dx.doi.org/10.9790/2834-09270713.

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Janicki, Marcin, Tomasz Torzewicz, Przemysław Ptak, Tomasz Raszkowski, Agnieszka Samson, and Krzysztof Górecki. "Parametric Compact Thermal Models of Power LEDs." Energies 12, no. 9 (May 7, 2019): 1724. http://dx.doi.org/10.3390/en12091724.

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Light-emitting diodes are nowadays the most dynamically developing type of light sources. Considering that temperature is the main factor affecting the electrical and lighting parameters of these devices, thermal models are essential subcomponents of the multidomain models commonly used for simulation of their operation. The authors investigated white power light-emitting diodes soldered to Metal Core Printed Circuit Boards (MCPCBs). The tested devices were placed in a light-tight box on a cold plate and their cooling curves were registered for different diode heating current values and various preset cold plate temperatures. These data allowed the computation of optical and real heating power values and consequently the generation of compact thermal models in the form of Foster and Cauer RC ladders. This also rendered possible the analysis of the influence of the considered factors on the compact model element values and their parametrization. The resulting models yield accurate values of diode junction temperature in most realistic operating conditions and they can be easily included in multidomain compact models of power light emitting diodes.

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Xiao, Peng, Junhua Huang, Dong Yan, Dongxiang Luo, Jian Yuan, Baiquan Liu, and Dong Liang. "Emergence of Nanoplatelet Light-Emitting Diodes." Materials 11, no. 8 (August 8, 2018): 1376. http://dx.doi.org/10.3390/ma11081376.

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Since 2014, nanoplatelet light-emitting diodes (NPL-LEDs) have been emerged as a new kind of LEDs. At first, NPL-LEDs are mainly realized by CdSe based NPLs. Since 2016, hybrid organic-inorganic perovskite NPLs are found to be effective to develop NPL-LEDs. In 2017, all-inorganic perovskite NPLs are also demonstrated for NPL-LEDs. Therefore, the development of NPL-LEDs is flourishing. In this review, the fundamental concepts of NPL-LEDs are first introduced, then the main approaches to realize NPL-LEDs are summarized and the recent progress of representative NPL-LEDs is highlighted, finally the challenges and opportunities for NPL-LEDs are presented.

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Nichols, M. "LEDs (light emitting diodes) in horticulture." Acta Horticulturae, no. 1176 (October 2017): 23–24. http://dx.doi.org/10.17660/actahortic.2017.1176.4.

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Barolet, Daniel. "Light-Emitting Diodes (LEDs) in Dermatology." Seminars in Cutaneous Medicine and Surgery 27, no. 4 (December 2008): 227–38. http://dx.doi.org/10.1016/j.sder.2008.08.003.

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Bourget, C. Michael. "An Introduction to Light-emitting Diodes." HortScience 43, no. 7 (December 2008): 1944–46. http://dx.doi.org/10.21273/hortsci.43.7.1944.

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Light-emitting diodes (LEDs) are semiconductor devices that produce noncoherent, narrow-spectrum light when forward voltage is applied. LEDs range in wavelength from the UVC band to infrared (IR) and are available in packages ranging from milliwatts to more than 10 W. The first LED was an IR-emitting device and was patented in 1961. In 1962, the first practical visible spectrum LED was developed. The first high-power (1-W) LEDs were developed in the late 1990s. LEDs create light through a semiconductor process rather than with a superheated element, ionized gas, or an arc discharge as in traditional light sources. The wavelength of the light emitted is determined by the materials used to form the semiconductor junction. LEDs produce more light per electrical watt than incandescent lamps with the latest devices rivaling fluorescent tubes in energy efficiency. They are solid-state devices, which are much more robust than any glass-envelope lamp and contain no hazardous materials like fluorescent lamps. LEDs also have a much longer lifetime than incandescent, fluorescent, and high-density discharge lamps (U.S. Dept. of Energy). Although LEDs possess many advantages over traditional light sources, a total system approach must be considered when designing an LED-based lighting system. LEDs do not radiate heat directly, but do produce heat that must be removed to ensure maximum performance and lifetime. LEDs require a constant-current DC power source rather than a standard AC line voltage. Finally, because LEDs are directional light sources, external optics may be necessary to produce the desired light distribution. A properly designed LED light system is capable of providing performance and a lifetime well beyond any traditional lighting source.

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Ma, Su, Yawei Qi, Ge Mu, Menglu Chen, and Xin Tang. "Multi-Color Light-Emitting Diodes." Coatings 13, no. 1 (January 13, 2023): 182. http://dx.doi.org/10.3390/coatings13010182.

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Multi-color light-emitting diodes (LEDs) with various advantages of color tunability, self-luminescence, wide viewing angles, high color contrast, low power consumption, and flexibility provide a wide range of applications including full-color display, augmented reality/virtual reality technology, and wearable healthcare systems. In this review, we introduce three main types of multi-color LEDs: the organic LED, colloidal quantum dots (CQDs) LED, and CQD–organic hybrid LED. Various strategies for realizing multi-color LEDs are discussed including red, green, and blue sub-pixel side-by-side arrangement; vertically stacked LED unit configuration; and stacked emitter layers in a single LED. Finally, according to their status and challenges, we present an outlook of multi-color devices. We hope this review can inspire researchers and make a contribution to the further improvement of multi-color LED technology.

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Nakamura, Shuji. "Blue-Green Light-Emitting Diodes and Violet Laser Diodes." MRS Bulletin 22, no. 2 (February 1997): 29–35. http://dx.doi.org/10.1557/s088376940003253x.

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Short-wavelength-emitting devices, such as blue laser diodes (LDs) and light-emitting diodes (LEDs), are currently sought for a number of applications, including full-color electroluminescent displays, laser printers, read-write laser sources for high-density information storage on magnetic and optical media, and sources for undersea optical communications. For these purposes, II–VI materials such as ZnSe and SiC, and III–V-nitride semiconductors such as GaN have been investigated intensively for a long time. However it was impossible to obtain high-brightness (over 1 cd) blue LEDs and reliable LDs. Much progress has been achieved recently on green LEDs and LDs using II–VI-based materials. The short lifetimes prevent II–VI-based devices from commercialization at present. The short lifetime of these II-VI-based devices may be caused by the crystal defects at a density of 103/cm2 because one crystal defect would cause the propagation of other defects leading to failure of the devices. Another wide-bandgap material for blue LEDs is SiC. The brightness of SiC blue LEDs is only between 10 mcd and 20 mcd because of the indirect bandgap of this material.On green LEDs, the external quantum efficiency of conventional, green GaP LEDs is only 0.1% due to the indirect bandgap of this material. The peak wavelength is 555 nm (yellowish green). As another material for green emission devices, AlInGaP has been used. The present performance of green AlInGaP LEDs is an emission wavelength of 570 nm (yellowish green) and maximum external quantum efficiency of 1%.

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Wang, Ming-Sheng, and Guo-Cong Guo. "Inorganic–organic hybrid white light phosphors." Chemical Communications 52, no. 90 (2016): 13194–204. http://dx.doi.org/10.1039/c6cc03184f.

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COLE, RICHARD W. "LIGHT EMITTING DIODES IN BIO-IMAGING." International Journal of High Speed Electronics and Systems 20, no. 02 (June 2011): 303–19. http://dx.doi.org/10.1142/s0129156411006611.

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Light-emitting diodes (LEDs) can and are currently integrated into light microscopes. They have numerous advantages as illumination sources. Most notably, they provide intensity (brightness) and spectral control during bio-imaging. For transmitted light imaging, LEDs can replace the traditional tungsten filament bulb, while offering longer life, little-to-no color temperature shift resulting from an intensity change, reduced emission in the infrared region, (a property important for live cell imaging), and reduced cost of ownership. For fluorescent imaging, in which the typical illumination sources are mercury or xenon lamps, LEDs offer the advantages of a longer lifespan, greater spatial and temporal stability, elimination of the need for mechanical shutters and neutral density filters, significantly lower cost of ownership, and reduction of photon dose at the specimen. Additionally, LEDs permit vibration-free, high-speed spectral and temporal modulation. This modulation allows more information to be obtained for a given photon dose.

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Mohamod Alkanze, Kamal Ali ,. "Study of Light-Emitting Diodes." Journal of The Faculty of Science and Technology, no. 5 (October 5, 2018): 1–3. http://dx.doi.org/10.52981/jfst.vi5.358.

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LEDs, or light-emitting diodes, are cheap, easy to purchase, and thus commonly used in physics instruction as indicators of electric current or as sources of light. In our opinion LEDs represent a unique piece of equipment that can be used to collect experimental evidence, and construct and test new ideas in almost every unit of a general physics course (and in many advanced courses) either as “black boxes” that allow students to study certain properties of a system of interest, as physical systems that allow students to learn an astonishing amount of physics that they usually do not encounter in a regular introductory physics course, and as non-traditional devices that allow students to construct concepts that are traditionally a part of a general physics course.

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Malevskaya A. V., Il’inskaya N. D., Kalyuzhnyy N. A., Malevskiy D. A., Zadiranov Y. M., Pokrovskiy P. V., Blokhin A. A., and Andreeva A. V. "Investigation of methods for texturing light-emitting diodes based on AlGaAs/GaAs heterostructures." Semiconductors 56, no. 13 (2022): 2081. http://dx.doi.org/10.21883/sc.2022.13.53906.9679.

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Investigations of methods for texturing the light-emitting surface of IR light-emitting diodes (LEDs) (wavelength 850 nm) based on AlGaAs/GaAs heterostructures with Bragg reflectors have been carried out. Developed were methods of liquid and plasma-chemical etching of solid solution for creating peaks (pyramids) of different form, 0.2-1.5 μm height. Estimation of the effect of texturing methods and also configuration of peaks on the light-emitting diode electroluminescence intensity has been performed. The increase of the electroluminescence intensity by 25% has been achieved. Keywords: light-emitting diode, texturing, etching methods, electroluminescence.

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Viñals, Roser, Olga Muñoz, Adrián Agustín, and Josep Vidal. "Multi-User Precoder Designs for RGB Visible Light Communication Systems." Sensors 20, no. 23 (November 29, 2020): 6836. http://dx.doi.org/10.3390/s20236836.

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In this paper, we design linear precoders for the downlink of a visible light communication (VLC) system that simultaneously serves multiple users. Instead of using phosphor-coated white light-emitting diodes (PWLEDs), we focus on Red-Green-Blue light-emitting diodes (RGB-LEDs) that allow modulating three separate data streams on the three primary colors of the RGB-LEDs. For this system, we design a zero-forcing (ZF) precoder that maximizes the weighted sum rate for a multilevel pulse amplitude modulation (M-PAM). The precoding design in RGB-based systems presents some challenges due to the system constraints, such as the limited power, the non-negative amplitude constraints per light-emitting diode (LED), and the need to guarantee white light emission while transmitting with RGB-LEDs. For comparison purposes, we also consider the ZF design for a PWLED-based system and evaluate the performance of both a PWLED- and an RGB-based system.

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Zainal, N., Abu Hassan Haslan, Hassan Zainuriah, M. Roslan Hashim, and Naser Mahmoud Ahmed. "Optimization of InGaN Based Light Emitting Diodes." Materials Science Forum 517 (June 2006): 195–201. http://dx.doi.org/10.4028/www.scientific.net/msf.517.195.

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The performance of InGaN quantum well based Light Emitting Diodes; (LEDs) had been numerically investigated by using standard industrial software, Silvaco. In this work, we found that InGaN single quantum well (SQW) LEDs gives better performance than InGaN triple quantum wells LEDs. The simulation results suggest that the inhomogeneity of electron and hole distributions in quantum wells active region plays an important role in the LEDs performance. The threshold current per μm also increases as the number of quantum well is increased.

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Zhou, Yuanming, Sijiong Mei, Dongwei Sun, Neng Liu, Fei Mei, Jinxia Xu, and Xianan Cao. "Improved Charge Injection and Transport of Light-Emitting Diodes Based on Two-Dimensional Materials." Applied Sciences 9, no. 19 (October 3, 2019): 4140. http://dx.doi.org/10.3390/app9194140.

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Light-emitting diodes (LEDs) are considered to be the most promising energy-saving technology for future lighting and display. Two-dimensional (2D) materials, a class of materials comprised of monolayer or few layers of atoms (or unit cells), have attracted much attention in recent years, due to their unique physical and chemical properties. Here, we summarize the recent advances on the applications of 2D materials for improving the performance of LEDs, including organic light emitting diodes (OLEDs), quantum dot light emitting diodes (QLEDs) and perovskite light emitting diodes (PeLEDs), using organic films, quantum dots and perovskite films as emission layers (EMLs), respectively. Two dimensional materials, including graphene and its derivatives and transition metal dichalcogenides (TMDs), can be employed as interlayers and dopant in composite functional layers for high-efficiency LEDs, suggesting the extensive application in LEDs. The functions of 2D materials used in LEDs include the improved work function, effective electron blocking, suppressed exciton quenching and reduced surface roughness. The potential application of 2D materials in PeLEDs is also presented and analyzed.

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Luo, Dongxiang, Lin Wang, Ying Qiu, Runda Huang, and Baiquan Liu. "Emergence of Impurity-Doped Nanocrystal Light-Emitting Diodes." Nanomaterials 10, no. 6 (June 24, 2020): 1226. http://dx.doi.org/10.3390/nano10061226.

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In recent years, impurity-doped nanocrystal light-emitting diodes (LEDs) have aroused both academic and industrial interest since they are highly promising to satisfy the increasing demand of display, lighting, and signaling technologies. Compared with undoped counterparts, impurity-doped nanocrystal LEDs have been demonstrated to possess many extraordinary characteristics including enhanced efficiency, increased luminance, reduced voltage, and prolonged stability. In this review, recent state-of-the-art concepts to achieve high-performance impurity-doped nanocrystal LEDs are summarized. Firstly, the fundamental concepts of impurity-doped nanocrystal LEDs are presented. Then, the strategies to enhance the performance of impurity-doped nanocrystal LEDs via both material design and device engineering are introduced. In particular, the emergence of three types of impurity-doped nanocrystal LEDs is comprehensively highlighted, namely impurity-doped colloidal quantum dot LEDs, impurity-doped perovskite LEDs, and impurity-doped colloidal quantum well LEDs. At last, the challenges and the opportunities to further improve the performance of impurity-doped nanocrystal LEDs are described.

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Remidi, K., A. Cheknane, and M. Haddadi. "Photovoltaic effect in Light Emitting Diodes." Algerian Journal of Signals and Systems 1, no. 1 (June 15, 2016): 30–36. http://dx.doi.org/10.51485/ajss.v1i1.16.

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This paper describes an experimental work on the electrical characterization of commercial LED of different colors and their photoelectric effect. A research work has been carried out to develop the experimental measurement in order to show the presence of a photovoltaic effect on LEDs. For this purpose, we measured the electrical characteristics of individual LED and studied their light intensities using a pyranometer EPLEY. This work focused mainly on red, green and yellowLEDs. Moreover, we have implemented an experimental system for the measurement of sensitivity of different LEDs depending on the power of light from a light source. A comparison was made between theoretical model and experimental results.

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JYOTHSNA J., SURAJ LUTHRA, and AYISHA SIDHIKA M. "LIGHT EMITTING DIODES IN VEGETABLE PRODUCTION SYSTMES." Asian Journal of Microbiology, Biotechnology & Environmental Sciences 24, no. 04 (2022): 746–50. http://dx.doi.org/10.53550/ajmbes.2022.v24i04.021.

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LEDs have become the predominant future lighting system for greenhouse crop production. The LEDs are popularly applied in photoperiod lighting, vegetable transplant production, graft-healing, greenhouse production and quality enhancement. As the LED technology advances, they improve the quality of vegetable transplants and produces. The spectral control reduce production costs and increase the value of specialty crops with promoted flavor and sensory traits. The Horticultural LED will continue to grow more hardware configurations and control protocols. LEDs provide comprehensive tool for plant environment for manipulation of plant function.

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Velpula, Ravi Teja, Barsha Jain, Ha Quoc Thang Bui, and Hieu Pham Trung Nguyen. "Full-Color III-Nitride Nanowire Light-Emitting Diodes." Journal of Advanced Engineering and Computation 3, no. 4 (December 31, 2019): 551. http://dx.doi.org/10.25073/jaec.201934.271.

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III-nitride nanowire-based light-emitting diodes (LEDs) have been intensively studied as promising candidates for future lighting technologies. Compared to conventional GaN-based planar LEDs, III-nitride nanowire LEDs exhibit numerous advantages including greatly reduced dislocation densities, polarization fields, and quantum-conned Stark effect due to the effective lateral stress relaxation, promising high-efficiency full-color LEDs. Beside these advantages, however, several issues have been identified as the limiting factors for further enhancing the nanowire LED quantum efficiency and light output power. Some of the most probable causes have been identified as due to the lack of carrier confinement in the active region, non-uniform carrier distribution, electron overflow, and the nonradiative recombination along the nanowire lateral surfaces. Moreover, the presence of large surface states and defects contribute significantly to the carrier loss in nanowire LEDs. Consequently, reported nanowire LEDs show relatively low output power. Recently, III-nitride core-shell nanowire LED structures have been reported as the most efficient nanowire white LEDs with a record-high output power which is more than 500 times stronger than that of nanowire white LEDs without using core-shell structure. In this context, we will review the current status, challenges, and approaches for the high-performance IIInitride nanowire LEDs. More specifically, we will describe the current methods for the fabrication of nanowire structures including top-down and bottom-up approaches, followed by characteristics of III-nitride nanowire LEDs. We will then discuss the carrier dynamics and loss mechanism in nanowire LEDs. The typical designs for the enhanced performance of III-nitride nanowire LEDs will be presented next. The color-tunable nanowire LEDs with emission wavelengths in the visible spectrum and phosphor-free nanowire white LEDs will be finally discussed.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

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Li, Tingting, Zhenyu Wang, Ying Zhang, and Zhennan Wu. "Engineering Coinage Metal Nanoclusters for Electroluminescent Light-Emitting Diodes." Nanomaterials 12, no. 21 (October 30, 2022): 3837. http://dx.doi.org/10.3390/nano12213837.

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Coinage metal nanoclusters (MNCs) are a new type of ultra-small nanoparticles on the sub-nanometer (typically < three nm) scale intermediate between atoms and plasmonic nanoparticles. At the same time, the ultra-small size and discrete energy levels of MNCs enable them to exhibit molecular-like energy gaps, and the total structure involving the metal core and surface ligand together leads to their unique properties. As a novel environmentally friendly chromophore, MNCs are promising candidates for the construction of electroluminescent light-emitting diodes (LEDs). However, a systematic summary is urgently needed to correlate the properties of MNCs with their influences on electroluminescent LED applications, describe the synthetic strategies of highly luminescent MNCs for LEDs’ construction, and discuss the general influencing factors of MNC-based electroluminescent LEDs. In this review, we first discuss relevant photoemissions of MNCs that may have major influences on the performance of MNC-based electroluminescent LEDs, and then demonstrate the main synthetic strategies of highly luminescent MNCs. To this end, we illustrate the recent development of electroluminescent LEDs based on MNCs and present our perspectives on the opportunities and challenges, which may shed light on the design of MNC-based electroluminescent LEDs in the near future.

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Bae, Jae-Hyun, Heui-Chun An, Mi-Gyeong Kim, Jin-Chul Park, Heum-Gi Park, and O.-Nam Kwon. "Adaptation of light emitting diode (LED) at culture on attachment plate of diatom." Journal of the Korean society of Fisheries Technology 50, no. 4 (November 30, 2014): 542–50. http://dx.doi.org/10.3796/ksft.2014.50.4.542.

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Neplokh, Vladimir, Vladimir Fedorov, Alexey Mozharov, Fedor Kochetkov, Konstantin Shugurov, Eduard Moiseev, Nuño Amador-Mendez, et al. "Red GaPAs/GaP Nanowire-Based Flexible Light-Emitting Diodes." Nanomaterials 11, no. 10 (September 29, 2021): 2549. http://dx.doi.org/10.3390/nano11102549.

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We demonstrate flexible red light-emitting diodes based on axial GaPAs/GaP heterostructured nanowires embedded in polydimethylsiloxane membranes with transparent electrodes involving single-walled carbon nanotubes. The GaPAs/GaP axial nanowire arrays were grown by molecular beam epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films has the main electroluminescence line at 670 nm. Membrane-based light-emitting diodes (LEDs) were compared with GaPAs/GaP NW array LED devices processed directly on Si growth substrate revealing similar electroluminescence properties. Demonstrated membrane-based red LEDs are opening an avenue for flexible full color inorganic devices.

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Stutte, Gary W. "Light-emitting Diodes for Manipulating the Phytochrome Apparatus." HortScience 44, no. 2 (April 2009): 231–34. http://dx.doi.org/10.21273/hortsci.44.2.231.

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Light-emitting diodes (LEDs) are solid-state, long-lived, durable sources of narrow-band light output that can be used in a range of horticultural and photobiological applications. LED technology is rapidly developing and high-quality, high-output LEDs are becoming commercially available at an affordable cost. LEDs provide the opportunity to optimize the spectra for a given plant response, but consideration must be given to both photosynthetic and photomorphogenic effects of light while making those selections. A discussion of basic phytochrome response and data necessary to select narrow-band LEDs to achieve a specific photostationary state is provided. The use of LEDs to alter spectral quality, and phytochrome equilibrium, to regulate anthocyanin formation in red leaf lettuce and to regulate flowering of short-day strawberry are discussed.

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Shaaban, M., S. Nasser, K. Youssef, and I. Yassin. "Capabilities and benefit of Light Emitting Diodes (LEDs)." International Conference on Electrical Engineering 11, no. 11 (April 1, 2018): 1–11. http://dx.doi.org/10.21608/iceeng.2018.30179.

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Kobayashi, Kent, Teresita Amore, and Michelle Lazaro. "Light-Emitting Diodes (LEDs) for Miniature Hydroponic Lettuce." Optics and Photonics Journal 03, no. 01 (2013): 74–77. http://dx.doi.org/10.4236/opj.2013.31012.

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Liu, Runzhong, and Ke Xu. "Blue perovskite light-emitting diodes (LEDs): A minireview." Instrumentation Science & Technology 48, no. 6 (May 12, 2020): 616–36. http://dx.doi.org/10.1080/10739149.2020.1762643.

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Schulze, Peter S. C., Luísa A. Barreira, Hugo G. C. Pereira, José A. Perales, and João C. S. Varela. "Light emitting diodes (LEDs) applied to microalgal production." Trends in Biotechnology 32, no. 8 (August 2014): 422–30. http://dx.doi.org/10.1016/j.tibtech.2014.06.001.

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Shang, Yuequn, and Zhijun Ning. "Colloidal quantum-dots surface and device structure engineering for high-performance light-emitting diodes." National Science Review 4, no. 2 (January 7, 2017): 170–83. http://dx.doi.org/10.1093/nsr/nww097.

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Abstract The application of colloidal quantum dots for light-emitting devices has attracted considerable attention in recent years, due to their unique optical properties such as size-dependent emission wavelength, sharp emission peak and high luminescent quantum yield. Tremendous efforts have been made to explore quantum dots for light-emission applications such as light-emitting diodes (LEDs) and light converters. The performance of quantum-dots-based light-emitting diodes (QD-LEDs) has been increasing rapidly in recent decades as the development of quantum-dots synthesis, surface-ligand engineering and device-architecture optimization. Recently, the external quantum efficiencies of red quantum-dots LEDs have exceeded 20.5% with good stability and narrow emission peak. In this review, we summarize the recent advances in QD-LEDs, focusing on quantum-dot surface engineering and device-architecture optimization.

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Zhang, Qiwei, Haiqin Sun, Tao Kuang, Ruiguang Xing, and Xihong Hao. "(K0.5Na0.5)NbO3:Eu3+/Bi3+: a novel, highly efficient, red light-emitting material with superior water resistance behavior." RSC Advances 5, no. 6 (2015): 4707–15. http://dx.doi.org/10.1039/c4ra10888d.

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Lin, Xiaoyu, Duo Liu, Guanjun Lin, Qian Zhang, Naikun Gao, Dongfang Zhao, Ran Jia, Zhiyuan Zuo, and Xiangang Xu. "Periodic indentation patterns fabricated on AlGaInP light emitting diodes and their effects on light extraction." RSC Adv. 4, no. 108 (2014): 63143–46. http://dx.doi.org/10.1039/c4ra11390j.

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Yan, Long, Xinyu Shen, Yu Zhang, Tieqiang Zhang, Xiaoyu Zhang, Yi Feng, Jingzhi Yin, Jun Zhao, and William W. Yu. "Near-infrared light emitting diodes using PbSe quantum dots." RSC Advances 5, no. 67 (2015): 54109–14. http://dx.doi.org/10.1039/c5ra08130k.

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The near-infrared light-emitting diodes using PbSe quantum dots were fabricated with the highest external quantum efficiency of 2.52%, which is comparable to those commercial InGaAsP LEDs and visible quantum dot electroluminescence LEDs.

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Guo, Yating, Feng Gao, Pan Huang, Rong Wu, Wanying Gu, Jing Wei, Fangze Liu, and Hongbo Li. "Light-Emitting Diodes Based on Two-Dimensional Nanoplatelets." Energy Material Advances 2022 (February 7, 2022): 1–24. http://dx.doi.org/10.34133/2022/9857943.

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Colloidal semiconductor nanocrystals (NCs) attract significant interest in recent years due to their narrow and tunable emission wavelength in the visible range, as well as high photoluminescence quantum yield (PLQY), which are highly desired in display technologies. The high-quality NCs have been recognized as vital luminescent materials in realizing next-generation display devices. With further development, NCs with near-unity PLQY have been successfully synthesized through engineering of the core/shell heterostructure. However, as the external quantum efficiency (EQE) of the nanocrystal light-emitting diodes (LEDs) approaches the theoretical limit of about 20%, the low out-coupling factor proposes a challenge of enhancing the performance of a device when using the spherical QDs. Hence, the anisotropic NCs like nanoplatelets (NPLs) are proposed as promising solutions to improve the performance of nanocrystal LEDs. In this review, we will summarize the synthetic strategies of two-dimensional (2D) NPLs at first. Then, we will introduce fundamental concepts of LEDs, the main approaches to realize LEDs based on nanoplatelets, and the recent progress. Finally, the challenges and opportunities of LEDs based on anisotropic NCs are also presented.

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Малевская, А. В., Н. Д. Ильинская, Н. А. Калюжный, Д. А. Малевский, Ю. М. Задиранов, П. В. Покровский, А. А. Блохин, and А. В. Андреева. "Исследование методов текстурирования светодиодов на основе гетероструктур AlGaAs/GaAs." Физика и техника полупроводников 55, no. 11 (2021): 1086. http://dx.doi.org/10.21883/ftp.2021.11.51565.9679.

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Investigations of methods for texturing the light-emitting surface of IR light-emitting diodes (LEDs) (wavelength 850 nm) based on AlGaAs/GaAs heterostructures with Bragg reflectors have been carried out. Developed were methods of liquid and plasma-chemical etching of solid solution for creating peaks (pyramids) of different form, 0.2–1.5 µm height. Estimation of the effect of texturing methods and also configuration of peaks on the light-emitting diode electroluminescence intensity has been performed. The increase of the electroluminescence intensity by 25% has been achieved.

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Janicki, Marcin, Przemysław Ptak, Tomasz Torzewicz, and Krzysztof Górecki. "Experimental Determination of Thermal Couplings in Packages Containing Multiple LEDs." Energies 16, no. 4 (February 15, 2023): 1923. http://dx.doi.org/10.3390/en16041923.

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Light Emitting Diodes (LEDs) are the most commonly used light sources. Temperature strongly affects their operation. Considering that multiple devices are often placed in a single housing, thermal couplings between devices become important. This problem is illustrated here based on the example of a light source containing four LEDs in a single package. Thermal analyses are carried out based on measured transient temperature responses. The measurement results are processed employing the Network Identification by Deconvolution method. The obtained results demonstrate clearly that depending on the device mounting manner and applied cooling condition the temperature rise value induced in neighboring devices can exceed 70% of the rise in the heating diode. Consequently, thermal models of such LEDs should consider not only self-heating effects, but also thermal interactions with the other diodes.

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Bauer, Stefan. "Blue-Light Hazard of Light-Emitting Diodes Assessed with Gaussian Functions." International Journal of Environmental Research and Public Health 18, no. 2 (January 14, 2021): 680. http://dx.doi.org/10.3390/ijerph18020680.

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The high blue proportion of phosphor-conversion white-light emitting diodes (pc-LEDs), especially of those with higher correlated color temperatures (CCT), raises concern about photochemically induced retinal damages. Although almost all general lighting service LEDs are safe, other applications exist, like spotlights for theatres or at construction sites, that can pose a severe blue-light hazard (BLH) risk, and their photobiological safety must be assessed. Because of required but challenging radiance measurements, a calculative approach can be supportive for risk assessment. It is the aim of this work to exploit Gaussian functions to study LED parameter variations affecting BLH exposure. Gaussian curve approximations for color LEDs, the BLH action spectrum, and the spectral luminous efficiency for photopic vision enabled analytically solving the BLH efficiency, ηB, and the BLH efficacy of luminous radiation, KB,v. It was found that sigmoidal functions describe the CCT dependence of ηB and KB,v for different color LEDs with equal spectral bandwidth. Regarding pc-LEDs, variations of peak wavelengths, intensities, and bandwidths led to linear or parabolic shaped chromaticity coordinate correlations. ηB and KB,v showed pronounced CCT dependent extrema that might be exploited to reduce BLH. Finally, an experimental test of the presented Gaussian approach yielded its successful applicability for color and pc-LEDs but a minor accuracy for blue and green LEDs.

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WINDER, STEVE. "LIGHT EMITTING DIODE DRIVERS AND CONTROL." International Journal of High Speed Electronics and Systems 20, no. 02 (June 2011): 267–86. http://dx.doi.org/10.1142/s0129156411006593.

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This paper outlines the various driving and control techniques for Light Emitting Diodes (LEDs). LEDs should be driven from a constant current source. High power LEDs are usually driven from a switching regulator, for reasons of efficiency. The types of drivers described include Buck (step-down), Boost (step-up) and Buck-Boost (step-up or step-down). Isolated drivers and Power Factor Correction (PFC) circuits are also described. This brief paper can only describe the basic outline of these circuits, but this should be sufficient to allow the basic principles to be understood.

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El-Ghoroury, Hussein S., Mikhail V. Kisin, and Chih-Li Chuang. "III-Nitride Multi-Quantum-Well Light Emitting Structures with Selective Carrier Injection." Applied Sciences 9, no. 18 (September 15, 2019): 3872. http://dx.doi.org/10.3390/app9183872.

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Incorporation into the multi-layered active region of a semiconductor light-emitting structure specially designed intermediate carrier blocking layers (IBLs) allows efficient control over the carrier injection distribution across the structure’s active region to match the application-driven device injection characteristics. This approach has been successfully applied to control the color characteristics of monolithic multi-color light-emitting diodes (LEDs). We further exemplify the method’s versatility by demonstrating the IBL design of III-nitride multiple-quantum-well (MQW) light-emitting diode with active quantum wells uniformly populated at LED operational current.

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Kwon, Tae-Rin, Sung-Eun Lee, Jong Hwan Kim, You Na Jang, Su-Young Kim, Seok Kyun Mun, Chan Woong Kim, Jungtae Na, and Beom Joon Kim. "310 nm UV-LEDs attenuate imiquimod-induced psoriasis-like skin lesions in C57BL/6 mice and inhibit IL-22-induced STAT3 expression in HaCaT cells." Photochemical & Photobiological Sciences 19, no. 8 (2020): 1009–21. http://dx.doi.org/10.1039/c9pp00444k.

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Sticklus, Jan, Peter Adam Hoeher, and Martin Hieronymi. "Experimental Characterization of Single-Color Power LEDs Used as Photodetectors." Sensors 20, no. 18 (September 11, 2020): 5200. http://dx.doi.org/10.3390/s20185200.

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Semiconductor-based light emitting diodes can be used for photon emission as well as for detection of photons. In this paper, we present a fair comparison between off-the-shelf power Light emitting diodes (LEDs) and a silicon photodetector with respect to their spectral, temporal, and spatial properties. The examined LED series features unexpected good sensitivity and distinct optical bandpass characteristic suitable for daylight filtering or color selectivity. Primary application is short range optical underwater communication, but results are generally applicable.

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Zavestovskaya, I. N., V. A. Gushchin, L. I. Russu, E. A. Cheshev, A. L. Koromyslov, I. M. Tupitsyn, A. A. Fronya, and M. S. Grigoryeva. "Inactivation of coronaviruses under irradiation by UVA-range light-emitting diodes." Quantum Electronics 52, no. 1 (January 1, 2022): 83–86. http://dx.doi.org/10.1070/qel17969.

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Abstract We report the results of the development of an experimental stand based on UVA light-emitting diodes (UVA LEDs) with radiation wavelengths of 385 and 395 nm for studying experimentally the inactivation of viruses of the coronavirus family, including SARS-CoV-2. Methodological grounds are presented for determining the inactivation dose that provides a predetermined decrease in the virus titre under the impact of UVA radiation. The effect of the diode radiation divergence on the virus photoinactivation process is investigated. It is shown that UVA LEDs can be used to reduce the virus titre by 4 orders of magnitude.

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Remidi, Kamel, A. Cheknane, and M. Haddadi. "Investigation of the Experimental Characterization of the Different Inorganic Light Emitting Diodes (LEDS) and the Photovoltaic Effect on These LED." International Journal of Power Electronics and Drive Systems (IJPEDS) 9, no. 3 (September 1, 2018): 1406. http://dx.doi.org/10.11591/ijpeds.v9.i3.pp1406-1411.

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<p>This paper describes our experiments on the electrical characterization of commercial light emitting diodes of different colors as well as their photoelectric effect. This experiment was conducted at the IMS of Bordeaux, which has a measurement bench allowing the intrinsic characterization of different light-emitting diodes in direct and reverse polarization. This bench also makes it possible to compare these experimental values with the theoretical values obtained by modeling.A second work done at the ENP of El-Harrach allowed us to put in place measurement means to show that there is a photovoltaic effect on the LEDs. For this purpose, we have measured the electrical characteristics of different LEDs and studied their light intensities using an EPLEY pyranometer. This work involved red, green , yellow ,white and blue LEDs. The photovoltaic behavior of light-emitting diodes (LEDs) was studied at ENP D'El Harrah Algeria, for a period of three days in March 2016. LEDs were exposed to solar radiation in the form of unitary units of LEDs. 9-16 hours These irradiated LEDs were monitored for photo-generated voltage and current at one-hour intervals. Solar radiation on a horizontal surface was measured using a Pyranometer.</p>

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Iida, Daisuke, and Kazuhiro Ohkawa. "Recent progress in red light-emitting diodes by III-nitride materials." Semiconductor Science and Technology 37, no. 1 (November 26, 2021): 013001. http://dx.doi.org/10.1088/1361-6641/ac3962.

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Abstract GaN-based light-emitting devices have the potential to realize all visible emissions with the same material system. These emitters are expected to be next-generation red, green, and blue displays and illumination tools. These emitting devices have been realized with highly efficient blue and green light-emitting diodes (LEDs) and laser diodes. Extending them to longer wavelength emissions remains challenging from an efficiency perspective. In the emerging research field of micro-LED displays, III-nitride red LEDs are in high demand to establish highly efficient devices like conventional blue and green systems. In this review, we describe fundamental issues in the development of red LEDs by III-nitrides. We also focus on the key role of growth techniques such as higher temperature growth, strain engineering, nanostructures, and Eu doping. The recent progress and prospect of developing III-nitride-based red light-emitting devices will be presented.

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Nguyen, Hieu P. T. "Editorial of Special Issue “Nanostructured Light-Emitters”." Micromachines 11, no. 6 (June 21, 2020): 601. http://dx.doi.org/10.3390/mi11060601.

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Significant progress has been made in the development of nanophotonic devices and the use of nanostructured materials for optoelectronic devices, including light-emitting diodes (LEDs) and laser diodes, has recently attracted tremendous attention due to the fact of their unique geometry [...]

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Zhang, Qiang, Cai-Feng Wang, Lu-Ting Ling, and Su Chen. "Fluorescent nanomaterial-derived white light-emitting diodes: what's going on." J. Mater. Chem. C 2, no. 22 (2014): 4358–73. http://dx.doi.org/10.1039/c4tc00048j.

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In this review, we highlight recent progress of fluorescent nanomaterial-derived white LEDs, including semiconductor nanocrystals or colloidal QD-based LEDs, carbon-based LEDs, silicon QD-based LEDs, and organic–inorganic fluorescent nanocomposite derived white LEDs.

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SHUR, MICHAEL, and ARTURAS ŽUKAUSKAS. "LIGHT EMITTING DIODES: TOWARD SMART LIGHTING." International Journal of High Speed Electronics and Systems 20, no. 02 (June 2011): 229–45. http://dx.doi.org/10.1142/s012915641100657x.

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We review the history and state-of-the-art of light emitting diode (LED). Unique properties of LEDs– high efficiency, long life time, flexibility in obtaining customized spectral power distribution, fast modulation rate, compact form factor, ability to generate radiation with wavelengths outside the visible range (infrared and ultraviolet, including deep ultraviolet) enable multiple applications for signage, display, general lighting, biology, medicine, agriculture, communications, industrial controls, security, and transportation. Many of emerging LED applications will be in "smart lighting", which are applications that are not possible or difficult to achieve using more traditional lighting sources.

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Taylor-Shaw, Elaine, Enrico Angioni, Neil J. Findlay, Benjamin Breig, Anto R. Inigo, Jochen Bruckbauer, David J. Wallis, Peter J. Skabara, and Robert W. Martin. "Cool to warm white light emission from hybrid inorganic/organic light-emitting diodes." Journal of Materials Chemistry C 4, no. 48 (2016): 11499–507. http://dx.doi.org/10.1039/c6tc03585j.

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The synthesis and characterisation of two novel organic down-converting molecules is disclosed, together with their performance as functional colour-converters in combination with inorganic blue light-emitting diodes (LEDs).

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Cinquino, Marco, Carmela Prontera, Marco Pugliese, Roberto Giannuzzi, Daniela Taurino, Giuseppe Gigli, and Vincenzo Maiorano. "Light-Emitting Textiles: Device Architectures, Working Principles, and Applications." Micromachines 12, no. 6 (June 2, 2021): 652. http://dx.doi.org/10.3390/mi12060652.

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E-textiles represent an emerging technology aiming toward the development of fabric with augmented functionalities, enabling the integration of displays, sensors, and other electronic components into textiles. Healthcare, protective clothing, fashion, and sports are a few examples application areas of e-textiles. Light-emitting textiles can have different applications: sensing, fashion, visual communication, light therapy, etc. Light emission can be integrated with textiles in different ways: fabricating light-emitting fibers and planar light-emitting textiles or employing side-emitting polymer optical fibers (POFs) coupled with light-emitting diodes (LEDs). Different kinds of technology have been investigated: alternating current electroluminescent devices (ACELs), inorganic and organic LEDs, and light-emitting electrochemical cells (LECs). The different device working principles and architectures are discussed in this review, highlighting the most relevant aspects and the possible approaches for their integration with textiles. Regarding POFs, the methodology to obtain side emissions and the critical aspects for their integration into textiles are discussed in this review. The main applications of light-emitting fabrics are illustrated, demonstrating that LEDs, alone or coupled with POFs, represent the most robust technology. On the other hand, OLEDs (Organic LEDs) are very promising for the future of light-emitting fabrics, but some issues still need to be addressed.

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Zheng, Yingqi, and Xiaozhang Zhu. "Recent Progress in Emerging Near-Infrared Emitting Materials for Light-Emitting Diode Applications." Organic Materials 02, no. 04 (October 2020): 253–81. http://dx.doi.org/10.1055/s-0040-1716488.

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In view of the wide applications of near-infrared (NIR) light in night vision, security, medicine, sensors, telecommunications, and military applications, and the scarcity of high-efficiency NIR-emitting materials, development of alternative NIR-emitting materials is urgently required. In this review, we focus on three kinds of emerging NIR-emitting materials used in light-emitting diodes (LEDs), namely organic materials, inorganic quantum dot (QD) materials, and organic–inorganic hybrid perovskite materials; the corresponding devices are organic LEDs, QD LEDs, and perovskite LEDs. The advantages and disadvantages of the three kinds of materials are discussed, some representative works are reviewed, and a brief outlook for these materials is provided.

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Dong, Dan, Weijie Wu, Lu Lian, Dongxu Feng, Yuezeng Su, Wanwan Li, and Gufeng He. "Enhanced performances of quantum dot light-emitting diodes with doped emitting layers by manipulating the charge carrier balance." Journal of Materials Chemistry C 5, no. 20 (2017): 5018–23. http://dx.doi.org/10.1039/c7tc01142c.

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Berry, R. James, Jay E. Harris, and Ronald R. Williams. "Light-Emitting Diodes as Sensors for Colorimetric Analyses." Applied Spectroscopy 51, no. 10 (October 1997): 1521–24. http://dx.doi.org/10.1366/0003702971939037.

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A new nondispersive colorimetric analyzer has been developed with the use of light-emitting diodes (LEDs) as optical sensors coupled to an artificial neural network (ANN). In this application, various colored LEDs are used as optical detectors with tuned bandpasses. The device has been evaluated against conventional spectrometric methods in the determination of pH and heavy metals by the use of colorimetric procedures. The spectrometer benefits from a simple design, ease of application, inexpensive cost of construction, and long life.

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Journal articles on the topic 'Light emitting diodes (LEDs)'

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