LED Color Research Articles

Performance improvement of microLED‐to‐microLED visible light communication using reverse bias

AbstractLED‐to‐LED visible light communication (VLC), which uses LEDs not only for the transmitter but also for the receiver, is being studied as an efficient optical wireless communication technology that uses LED lighting infrastructure. In this paper, we investigate microLED‐to‐LED VLC, which uses microLEDs as both the transmitter and receiver. In particular, we conducted a study to improve the performance of microLED‐to‐microLED VLC. For this, we measured the performance depending on the transmitter and receiver LED color combination. In addition, the effects of zero bias and reverse bias at the receiver LED were investigated. We also investigated the improvement in the reverse bias when applying a transimpedance amplifier to the receiver LED. Finally, we experimentally demonstrated a data rate of 360 kbps in the microLED‐to‐microLED VLC.

Blue perovskite LEDs improved with in situ fabrication technique

Researchers have created bright blue perovskite LEDs, finishing the trifecta of LED colors needed to enable commercial applications.

A dual-parameter evaluation method for color-enhancement technologies and its application to lighting-spectrum optimization for color-deficient observers

Over 200 million people worldwide suffer from color vision deficiency (CVD), leading to a compromised perception of the color world. Despite the availability of various color enhancement technologies (CETs), assessing their actual performance has remained challenging due to the lack of a comprehensive evaluation method. In this paper, we propose a dual-parameter metric system that quantitatively evaluates CETs' capacity to improve CDOs' color discrimination ability and color fidelity relative to color-normal observers (CNOs). We validated this method by comparing its evaluation results with those of prior studies that relied on psychophysical experiments. Our proposed dual-parameter evaluation system can also be employed to optimize CET-based solutions. As a preliminary exploration, we optimized lighting spectra using LED color mixing for CVD-friendly illumination applications, which demonstrated a clear improvement in color vision for color-deficient observers while maintaining good color fidelity for CNOs’ color vision.

Design and simulation of 2D Ruddlesden–Popper perovskite solar cells under LED illumination: Role of ETL and front contact band alignment

This paper focuses on the design and simulation of 2D Ruddlesden-Popper halide perovskite (RPHP) solar cells, emphasizing their optimization for indoor LED illumination conditions. The design process begins with the validation of physical models within the SCAPS device simulator, accomplished through careful calibration against experimental (MAMP)MAn−1PbnI3n+1 RPHP cell data. Subsequently, different values of <n> (with n = 1, 2, 3, and 4) are explored to study the impact of different band gap energies, aiming to identify the most suitable option for optimal efficiency across diverse LED color temperatures. By addressing both material-specific considerations and device architecture optimization, this study aims to establish a comprehensive framework for designing RPHP solar cells tailored for white LED illumination. Additionally, the simulation reveals that optimizing the electron affinity of the Electron Transport Layer (ETL) significantly impacts device performance, with efficiencies exceeding 25 %. Furthermore, the study discusses emerging trends such as ETL-free structures, which aim to address interface defects and enhance device performance. In addition, we analyze the impact of bulk trap density and thickness of the 2-D perovskite absorber on efficiency limitations. With an absorber thickness set at 800 nm, a marginal decrease in PCE is observed, for the ETL-free solar cell, from around 34 % to 32 % as the trap density ranges from 1011 to 1014 cm−3. In contrast, for the ETL-based structure with the same variations, PCE experiences a substantial decline, dropping from approximately 47 % to 37 %. While the ETL-free structure may exhibit a lower PCE compared to the ETL-based cell, its capacity to endure fluctuations in trap density offers a notable advantage.These efforts underscore the potential of 2D RPHP photovoltaic cells for indoor applications, presenting a pathway towards efficient, stable, and cost-effective photovoltaic technology suited for diverse lighting environments.

Modification of the composition of thyme (Thymus vulgaris) essential oil based on the quality of the light

Objective: To identify the changes in the concentration of the main components of thyme (Thymus vulgaris) essential oil in response to five different LED colors. Design/Methodology/Approach: A completely randomized experimental design was used. The design included five treatments (white light; blue light; red light; 75% blue light and 25% red light; and 75% red light and 75% blue light) and 10 repetitions, at a 25 μmol m−2 s−1 luminous intensity, during a 16 h photoperiod. The thyme plants were sown in a pot with a substrate made up of 50% peat, 48% perlite, and 2% vermicompost. Each plant was an experimental unit. The plants were placed in light isolation chambers and subjected to the treatment for 35 days. Results: The concentration of the main molecules in the essential oil recorded considerable changes between treatments: the concentration of thymol (its main component) increased in the white light treatments, as well as in the red light (75%) and blue light (75%) treatments. In addition, the composition of the essential oil resulting from these treatments is different to the composition reported in the references. Study Limitations/Implications: The light intensity used in this experiment was lower than the light intensity required for plant growth; however, it was enough to produce changes in the secondary metabolism. Findings/Conclusions: The changes in the quality of the light modify the composition of the thyme essential oil. Even at a low light intensity (25 µmol m-2 s-1), the changes in the spectrum composition under which the plants grow influence the composition of the essential oil.

Uniform Lighting of High-Power LEDs at a Short Distance to Plants for Energy-Saving and High-Density Indoor Farming

A tunable LED panel with multiple types of LEDs on a panel can provide various spectra for optimal plant growth. However, it is difficult for a lighting panel with multiple types of high-power LEDs to achieve uniform lighting. We demonstrated that by using optical reflectors at the sides of an LED panel to trap photons of LED arrays or using both the above-mentioned reflectors and optical lenses on each LED, high lighting uniformity can be achieved at a short distance to plants. The ray tracing simulation results show that the LED panel equipped with reflectors and optical lenses can achieve a high uniformity of &gt;0.80 when the LED-plant distance is at half of the LED array’s pitch. We further verified that an LED panel (at a size of 88 cm × 54 cm) installed with reflectors can achieve light uniformities around 0.90 at a 15 cm LED-plant distance for the 6 types of LEDs (4 color LEDs and 2 white LEDs) on the panel. Compared with a branded tunable LED panel, our LED panel saves &gt;25 cm vertical distance for each tier of plants and has 92.5% higher photon efficacy for 660 nm LEDs that exist on both panels.

Portable Air Quality Detector Using DSM501A Dust Sensor and Arduino Uno

Aims: The primary feature of this research is to design a circuit that can analyze the air around the system and determine the quality of the air.&#x0D; Study Design: This paper reports on the design and implementation of a portable air pollution analyzer using Arduino Uno, DSM501A dust sensor, LCD, switches, buzzer, and multiple LEDs. The air pollution analyzer system was designed using a combination of hardware and software techniques to measure air pollution properly.&#x0D; Place and Period of Study: The research was accomplished by the authors in a group of two students under the grasp of a professor as a part of one of his course capstone projects for the Bachelor of Science in Electrical and Electronic Engineering degree at the American International University Bangladesh (AIUB), Dhaka, Bangladesh. The authors performed their investigative tasks at AIUB from September 2023 to February 2024.&#x0D; Methodology: The air pollution analyzer was implemented using an Arduino Uno and dust sensor to generate and determine accurate air quality based on specific air contents. The system that was developed used a PM10 detection system that identified the amount of dust particles in the area. Based on PM10 readings, the air quality was identified. Moreover, the Air Quality Index (AQI) was determined using the PM10 readings. The LCD, buzzer, and multiple LEDs were used to display and indicate the air quality condition and levels.&#x0D; Results: The portable air pollution analyzer was successfully tested and found to be accurate and reliable in determining air quality. To indicate different hazardous states of air, red, green, and yellow color LEDs are used. The test outcomes were very satisfactory.&#x0D; Conclusion: This system demonstrates the use of a microcontroller in building a simple yet effective portable air quality detector. It can be scaled up for commercial production.

Study the Effect of Colored and White LED Light Radiation on the Biological Activity of Desmonostoc alborizicum Cultivated Under Modified BG-110 Medium Composition

Study the Effect of Colored and White LED Light Radiation on the Biological Activity of Desmonostoc alborizicum Cultivated Under Modified BG-110 Medium Composition

Design and performance evaluation of a pendulous piezoelectric rotational energy harvester through magnetic plucking of a fan-shaped hanging composite plate

Over the past decade, there has been significant interest in harvesting energy from rotational motion through piezoelectric transduction, with the aim of providing energy-autonomous structural health monitoring systems for rotating machinery. Unlike most existing separated-type magnetically plucked piezoelectric rotational energy harvesters (PREHs) where a separate stationary support is frequently required to place either exciting or excited magnets, we proposed a pendulous piezoelectric rotational energy harvester (P-PREH) which was characterized by the structural integration and simultaneous motion of the piezoelectric transducer and actuator to harvest energy from rotating machines without stationary support. Structure simulation, fabrication, and experimental testing were performed to verify the structural feasibility and investigate the effect of structure and exciting parameters. The results showed that the P-PREH can generate relatively stable output voltage within a wide range of rotary speeds because of the random swing of exciting disk. Besides, the load resistance-dependent power indicated that P-PREH with swing radius of proof mass of 160 mm and the exciting magnet quantity ratio of 0.82 could yield a maximum output power of 0.65 mW at 20 kΩ and 1120 r/min. Also, 50 blue LEDs, array of different color LEDs and a low-power light strip could be lighted by the P-PREH.

Human centric lighting luminaires: practical design

Discoveries in medicine concerning the influence of light on human physiology provoked the creation of the Human Centric Lighting (HCL) approach. Research dedicated to this mainly focuses on optimally matching light parameters to human needs, e.g. increasing concentration, relaxation, etc. However, only a properly designed light source is capable of meeting HCL goals. This paper focuses on the LED luminaire design used in HCL systems. A review of LEDs dedicated to HCL systems was performed. Their advantages and disadvantages are discussed. The Tunable White (TW) design is shown to be the most universal solution for HCL systems because it enables regulation of the colour temperature and spectrum, depending on user needs. However, TW is also the most complex in design. The problems that might arise during TW luminaire design are discussed. Example strategies on how to solve them, focusing on colour mixing and LED arrangement are given. Practical examples of TW luminaire design are also described, each one with a commentary covering encountered issues and their solutions.

Illumination Effects on Bacteriorhodopsin Accumulation in Archaeon Halobacterium Halobium

Highlights Effects of varying illumination conditions, including light intensity, light color, and illumination pattern on archaeon Halobacterium halobium growth and bacteriorhodopsin (BR) accumulation were first evaluated. LED green light was much more energy-efficient than the red and blue lights in this research. If energy consumption was not a concern, LED blue and red lights (or their combinations) were more effective for cell growth and BR accumulation, respectively, with a similar light intensity. Abstract. This study was to understand the effect of LED light intensity, color, and illumination pattern on the growth of and bacteriorhodopsin (BR) accumulation in archaeon Halobacterium halobium. Experimental results showed that archaeon growth and BR content increased with increasing white light intensity. Green and white LED lights were found to be the most effective for archaeon growth and BR accumulation; here, effectiveness is defined based on photons shined on the bioreactor. The 12-h light/12-h dark cycle illumination pattern resulted in longer lag phase but achieved higher final cell growth and BR accumulation than continuous white light or an instant flash of light/dark illumination. The fade pattern that had smooth transitioning among green, blue, and red lights was better than the jump pattern without transitioning. The highest cell dry weight and BR content of H. halobium were 1.84 g l-1 and 11.76 mg l-1, respectively, under 29.85 µmol/m2s LED white light illumination. The green LED light of 1.39 µmol/m2s had the highest energy-specific conversion effectiveness and saved energy consumption by 84 and 87% per cell biomass and BR dry weight, respectively, compared to the worst case of LED white light of 29.85 µmol/m2s. Keywords: Archaeon, Bacteriorhodopsin, Halobacterium halobium, Illumination pattern, LED light, Light color.

New portable device for an examination of visual cognitive evoked potentials might extend their diagnostic applications in psychiatry

Despite positive prior results obtained by using event-related potentials (ERPs) in psychiatric patients, they are not routinely used in the clinical setting. This may in part be due to problems regarding a lack of transportable equipment availability. It can be difficult for these patients to repeatedly visit electrophysiological laboratories. To address this issue, we propose using a new, fully portable device for visually evoked potentials (VEP) and cognitive function assessment, that can be used for quick examinations (https://www.veppeak.com). Our device, called “VEPpeak”, is built into a headset with a color LED visual stimulator. It weighs 390 g and is connected to a notebook (PC) with evaluation software via USB. In this pilot study, we verified the device's usability in 31 patients with schizophrenia. We used the oddball paradigm with the recognition of colors for the P300 wave and choice reaction time evaluation. The examination lasted only about ten minutes. The results indicated good reproducibility of large cognitive potentials (P300) with prolonged P300 latencies and reduced amplitudes in patients compared to 15 control subjects. The P300 latency and reaction time prolongation in patients correlated with their age and the sedative effect of the pharmacotherapy.

Going beyond the 20th century color space to evaluate LED color consistency.

The color matching possibilities between (reference) phosphor-converted LEDs (pc-LEDs) and replacement metameric LEDs made by color mixing technology (cm-LEDs) were evaluated in the classical 20th century CIE 1976 color space developed for perpendicular viewing (based on a 2° colorimetric observer) and in the latest CIE 2015 cone fundamental color space developed for wide field of view observers (10° colorimetric observer). For each given pc-LED 10 different sets of cm-LEDs were designed and evaluated for color consistency in 2°and 10° color spaces. There were 10 different B-color LEDs considered along with constant RGA LEDs. There are thousands of possible distributions that are metameric in the CIE 1976 color space and thousands of possible distributions that are metameric in the CIE 2015 color space for each set of LEDs. From the population of SPDs, we selected 10 metameric SPDs characterized by maximum differences between chromaticities. The results provide evidence that evaluating LED color consistency based only on the CIE 1976 color space is not fully informative because it may provide inaccurate information about light color consistency when the observer has a wide field of view. There are cases showed in this paper where cm-LEDs are color consistent in the CIE 2015 color space but are not color consistent in the CIE 1976 color space and vice versa. Including color consistency in the new CIE 2015 color space should be treated as an additional evaluation tool proving the user additional information relevant to the intended use of the LED. The results illustrate differences in LED color consistency evaluated in different color spaces and provides incentive go beyond the 20th century color space in the evaluation of cm-LED color consistency.

Multi-walled carbon nanotubes decorated ZnMoO4 nanoflakes and their supercapacitive property

In this work, multi-walled carbon nanotubes decorated ZnMoO4 nanoflakes are synthesized by facile and rapid template-free hydrothermal approach. The prepared materials are characterized by various characteristic techniques. The synthesized materials are subjected as electrode materials for supercapacitive properties. The specific capacitance of 737 F g−1 is obtained at the current density of 1 A g−1 from ZnMoO4 nanoflakes. Further, the capacitance of prepared material is improved by doping a small amount of multiwall carbon nanotubes (MWCNTs). As a result, the specific capacitance of 1004 F g−1 is observed at 1 A g−1 from MWCNT/ZnMoO4 composite. The constancy of the prepared materials is performed up to 5000 cycles at 5 A g−1. Further, aqueous asymmetric supercapacitor is also designed by MWCNT/ZnMoO4 (as positive electrode) and activated carbon (AC) (as negative electrode). The high energy density of 28.61 W h kg−1 is calculated with power density of 725.52 W kg−1 from MWCNT/ZnMoO4//AC device. In addition, two yellow color LEDs are also powered by series connected two MWCNT/ZnMoO4//AC devices.

Preference of pear psyllid (Cacopsylla pyri) for specific colour inspires new application in plant protection

AbstractUnderstanding the cues used by insects to select their hosts is essential for developing sustainable control strategies, particularly for plant disease vectors. Pear psyllids (Cacopsylla pyri) are vectors of the bacterial disease pear decline caused by ‘Candidatus Phytoplasma pyri’. Yellow sticky traps are typically used to monitor pest insects, but they are non‐specific and capture many beneficial insects, too. Against the background of improving visual traps, this research aimed to investigate the colour choice behaviour of C. pyri. Our first approach was to screen insect colour preferences by performing choice assays with different LED colour wavelengths in a small‐scale choice arena under controlled conditions. Over six LEDs tested, there was a strong significant preference of C. pyri for green 1 (532 nm) followed by green 2 (549 nm). Yellow (576 nm), orange (593 nm), red 1 (619 nm) and red 2 (633 nm) were less attractive than green. Subsequently, the trapping of pear psyllids was tested in the field using newly developed traps covered with transparent‐coloured PVC sheets with a similar wavelength of the preferred LEDs. Red and completely transparent traps have been used as control and combined in randomized blocks in a pear orchard. Field trials revealed that green traps ranging from 525 to 537 nm attracted significantly more pear psyllids than longer wavelength green (543 nm), red and transparent ones. The construction of specific green‐coloured sticky traps seems promising for improving psyllid trapping, especially during an early infestation at low population densities. Thus, these visual traps should be considered in future and integrated into psyllid monitoring as part of integrated pest management.

Dynamic visible light positioning based on enhanced visual target tracking

In visible light positioning systems, some scholars have proposed target tracking algorithms to balance the relationship among positioning accuracy, real-time performance, and robustness. However, there are still two problems: (1) When the captured LED disappears and the uncertain LED reappears, existing tracking algorithms may recognize the landmark in error; (2) The receiver is not always able to achieve positioning under various moving statuses. In this paper, we propose an enhanced visual target tracking algorithm to solve the above problems. First, we design the lightweight recognition/demodulation mechanism, which combines Kalman filtering with simple image preprocessing to quickly track and accurately demodulate the landmark. Then, we use the Gaussian mixture model and the LED color feature to enable the system to achieve positioning, when the receiver is under various moving statuses. Experimental results show that our system can achieve high-precision dynamic positioning and improve the system's comprehensive performance.

Poster Session: Threshold versus intensity curves measured with a new high-brightness display system.

Classical threshold vs. intensity (tvi) curves were measured using optical systems and were generally limited to increment test stimuli and relatively simple spatial patterns. Modern displays provide more flexibility in terms of stimuli spatial profiles but are usually dim enough that there may be rod intrusion when measuring cone responses. Here we describe a high-brightness display system and present tvi's for increment and decrement achromatic tests. The system consists of a PROPixx three-chip DLP LED color projector (VPixx Technologies, Saint-Bruno, Canada) controlled via a Datapixx display driver, with 12-bit digital to analog conversion per RGB channel. Light from the projector is collected in a large diameter lens and focused on high gain rear projection screen. Retinal illuminance of the background may be varied in three ways: (a) varying the mean current supplied to the LEDs from the controller (adjustable in software); (b) using calibrated neutral density filters mounted near the eye; and (c) changing the midpoint of the RGB channels in software (e.g., making the white background as R=G=B=0.1 instead of 0.5). Method (c) is made easier by the fact that the PROPixx "gamma curve" is linear, which also means that no RGB bits are lost to gamma correction. We will show thresholds for achromatic tests on a white background varying from 0.56 to 4.03 log trolands, with preliminary results suggesting differences in the tvi curves between the increment and decrement tests.

Construction of multi walled carbon nanotube decorated CoMn2O4 hexagonal nanoplates for high performance aqueous asymmetric supercapacitor

The fabrication of transition metal oxide with carbonaceous material results in hybrid electrode with good charge storage capacity, higher energy density and power density than transition metal oxide electrodes. In this work, hybrid electrode material of CoMn2O4 hexagonal nanoplates and multi-walled carbon nanotubes (MWCNTs) is synthesized by co-precipitation process. The transmission electron microscope (TEM) analysis of prepared material shows that CoMn2O4 nanoplates are uniformly anchored on MWCNTs which helps to keep good electronic channel throughout the electrode material. Further, the MWCNT/CoMn2O4 is widely examined as high-performance electrode material in supercapacitor and, its capacitive faradaic charge storage mechanism is studied. The synergistic interaction between MWCNTs and CoMn2O4 hexagonal nanoplates resulted in the specific capacity of 156.75 mAh g−1 at 1 A g−1 which is higher from the specific capacity of sole CoMn2O4 nanoplates (113.37 mAh g−1 at 1 A g−1). Further, asymmetric supercapacitor is designed and high energy density of 58.41 W h kg−1 is observed at power density of 502.5 W kg−1. Furthermore, four parallel connected yellow color LEDs and a toy motor fan are functionalized by MWCNT/CoMn2O4//AC device.

Multi-walled carbon nanotube decorated CoS microspheres and their supercapacitive properties

In the present work, microspheres of CoS are synthesized by most adoptable hydrothermal method. The synthesized material is figured out by numerous characteristic techniques. Further, the prepared CoS material is used as electrode material for supercapacitor and high specific capacity of 112.62 mAh g−1 is obtained at 1 A g−1. Furthermore, the capacity of sole product is boosted by adding a small amount of multi-walled carbon nanotubes (MWCNTs) and improved specific capacity of 158 mAh g−1 is obtained from MWCNT/CoS at 1 A g−1. Owing to high specific capacity of composite, aqueous asymmetric supercapacitor (ASC) is designed by MWCNT/CoS as a positive electrode and activated carbon (AC) as a negative electrode. The high energy density of 31.6 W h kg−1 is obtained at the power density of 750 Wh kg−1 from MWCNT/CoS//AC. In addition, two parallel connected red color LEDs, kitchen timer and a motor fan are functionalized by two MWCNT/CoS//AC devices.

Development and performance evaluation of a wheel-type cantilevered piezoelectric rotational energy harvester via an unfixed exciting magnet

A wheel-type cantilevered piezoelectric rotational energy harvester (wheel-type PREH) via an unfixed exciting magnet was presented to harvest energy from rotational motion without or far away from a fixed support. To verify the structural feasibility and figure out the effect of rolling exciting magnet and excited magnet on the dynamic characteristics and power generation performance of the wheel-type PREH, the theoretical analysis, simulation, fabrication and experimental testing were performed. The results showed that the performance of the wheel-type PREH depended on the rotary speeds, proof mass and piezo-cantilever mass, number of exciting magnets, cylindrical sleeve materials and so on. When other parameters were constant, there were multiple optimal rotary speeds for the maximal amplitude-ratio, output voltage, electrical energy and output power to achieve peak. Besides, the total number of voltage crests per second did not change with rotary speed. There was a constant optimal resistance load for the wheel-type PREH at different rotary speeds to achieve maximal power. The PREH prototype could yield a maximum output power of 0.74 mW at 767 r/min with optimal load resistance of 215 kΩ and 40 different color LEDs in parallel and a low power light strip could be lighted by wheel-type PREH.