LED lighting is the mainstream of the global energy conservation, and high-power LED lighting is the main trend of the future world of lighting lighting system. High-power LED with high brightness, energy saving and environmental protection, safety and high stability, energy-saving than traditional light sources 60% to 70%.
The traditional sound and light control delay controller can achieve good control of the lights in the dark, or come in the evening when the light comes, can effectively achieve "people to light, people go lights out", but because of its switch is used relay like mechanical controllers, so many places in the flow of people due to frequent switching, relatively easily damaged.
According to the existing high-power led high bay light manufacturers products on the market, designed to be applied in corridors, staircases, classrooms and other places of intelligent lighting systems.
The system uses 24 V / 3 A switching power supply, the lower level can be distributed multiple LED intelligent lighting module (see Figure 1). Controller using AT89C2051, constant current drive using PT4115 chip. Bright lights off and brightness by dimming realization and change.
DIM end PT4115 chip available to achieve the output current PWM dimming from 0-100% adjustment, according to the characteristics, design a set of voice control, light control, time control in one of the intelligent dimming module. Its functions are:
(1) When the light (natural light) time, with or without sound, light does not shine.
(2) When no light (natural light) when, if a man produces sound through the controller to determine the time period, if the sky is completely dark down time (defined as the first period), then the LED emitted 100% brightness. The rest of the time period that the sky still bright, the controller can output a 50% duty cycle square wave, so that the brightness of LED 50% will be issued, which can further save energy, improve energy efficiency.
A constant current driver based PT4115
1. 1 PT4115 chip introduced
PT4115 is a step-down constant current source inductor current continuous conduction mode for driving single or multiple series LED.PT4115 input voltage range of 6 V ~ 30 V, adjustable output current of up to 1. 2A Depending on the input voltage and external components, PT4115 can drive up to tens of watts LED.PT4115 built-in power switch, the use of high-current sample set average LED current, and by D IM pin can accept analog dimming and a wide range of PWM dimming. D IM when the voltage is lower than 0. 3 V, the power switch is turned off, PT4115 enters a low current standby mode.
1. 2 LED spotlights drive circuit
When V IN power-inductance (L) and the current sense resistor (RS) of the initial current is zero, LED output current is zero (see Figure 2). At this time, the output switch is turned on, the potential SW is low. Current through the inductor (L), current sense resistor (RS), LED and internal power switch from V IN to ground, the slope of the current rise from V IN, inductance (L) and LED drop decided to produce a pressure in RS poor VCSN, when (V IN-VCSN) "115 mV, the internal power switch is turned off, the current flowing through the inductor to another slope (L), current sense resistor (RS), LED and Schottky diode (D); as (V IN-VCSN) "when 85mV, power switch back on, which makes the average current in the LED is IOUT = (0. 085+ 0. 015) / 2? RS = 0. 1 / R S. If you do not use the dimming function enables DIM pin floating, then set the maximum output current.
2 Based Top249Y of 72W switching power adapter design
2.1 Transformer Design
High-frequency transformer design should pay attention to: 1) the high-frequency transformer design, at maximum output power, the core of the magnetic flux density should reach saturation, in order to avoid distortion at large signal. 2) In the transient process, the high-frequency leakage inductance and stray capacitance chain will cause inrush current and peak voltage and pulse oscillation top, so the loss increases, the switch will cause serious damage. Meanwhile, the output winding turns and more layers for a long time, you should consider the impact of distributed capacitance, reducing the distributed capacitance help to curb high-frequency signal to interference load. The same high-frequency transformer while reducing the distributed capacitance and leakage inductance is difficult, depending on the job requirements should ensure proper capacitance and inductance.
2.2 switching power supply circuit
Figure 3 C 6 for X-type capacitors, filter series mode interference between the grid. L2 is the common mode suppressor, can filter out common mode interference, C 1 is the input filter capacitor. Use a resistance value R 11 2MΩ realization undervoltage and overvoltage detection, while providing lower output voltage ripple frequency voltage feedforward.
TOP249Y in this circuit DC voltage range of 100 ~ 450 V, once beyond the voltage range, TOP249Y will automatically shut down. Resistor R 10 20. 5 K using an external resistor value from the current limit set to full peak current is only slightly higher than the low-voltage work, allowing the use of smaller transformer core, while avoiding the start and output load transients the core saturation. VR1 that instantaneous voltage suppression tube model is P6KE200, in parallel with the capacitor C 11 in order to reduce the loss of Zener clamp. Models available for blocking diode D1 UF4006. Target clamping voltage averages about 180 VR 4, R 5, R 6 is the output voltage of the sampling resistor, after sampling and TL431 internal reference voltage to generate an error voltage, and then PC817A optocoupler feedback to the control pin C, and then change the output duty TOP249Y to stabilize the output voltage.
3 AT89C2051 based intelligent controller
Shown, which is mainly composed of a sensor unit, A \ D conversion unit, the controller unit 4 based composition AT89C2051 intelligent controller circuit. AT89C2051 chip for voice and light control signals from the sensor detects the signal data through plastic surgery done after treatment, and then control the LED driver. The circuit of AT89C2051 p3. 0 and p3. 1 as an input signal detecting port, and the remaining 13 ports selectable output control. Software flow chart shown in Figure 5.
4 Summary
led high bay light for sale designed by the author, can effectively monitor, detect changes in the surrounding environment, and promptly closed, open source, and dimming lights. The system as compared with conventional sound and light control delay switch illumination system, not only can save a lot of energy, but its unique dimming module using the electricity efficiency is greatly improved. The system is in the works have a good prospect.
Thursday, December 4, 2014
Tuesday, December 2, 2014
China's LED industry is expected to enter the explosive growth
Guangzhou Xinhua October 17 (Reporter Wu Weihong) Recently, the reporter learned that, with the light-emitting diode (LED) and other green energy in the universal application of the globe, our LED lighting products export is in rapid growth. Insiders said that the current LED industry, strong export and domestic market potential is huge, the next few years, led high bay light price is expected to usher in the explosive growth.
In the 116th Canton Fair lighting exhibition, the reporter saw domestic companies have exhibited a wide variety of LED lighting, some companies develop new products can be manipulated using Bluetooth, a number of new product design novel also won the Fair because of export products design Awards attracted many overseas businessmen to consult.
"This year's LED export situation is very good, stable export markets in developed countries, emerging countries has grown rapidly in the next few years, the domestic market is expected to show explosive growth." LED lighting division, general manager of Shenzhen Mao-Xin Dai Yuanqing electronics company forecast.
Insiders said that the blue LED chips before the invention, can not be applied to the specific white lighting. The emergence of true blue LED into the home, road and landscape outdoor stage large-scale applications, and to subvert the era incandescent and energy-saving lamps, helps to reduce carbon emissions and environmental protection.
Director of the Joint Innovation Center of Guangdong Province semiconductor lighting industry assistant Li Wenyu told reporters that the current rapid development of LED industry, market prospects. Guangdong Province last year, LED exports reached 60 billion yuan, of which the Russian market is growing very fast, the growth rate of 100%.
According to the authoritative estimates, the next 3-5 years, China's LED lighting products exports will remain 40% annual growth, which slowed down the growth rate of the European and American markets, the strong growth in emerging markets.
According to China CCCME, currently Russia, Southeast Asia and the Middle East are our LED lighting products export orders the fastest growing overseas markets.
"At present, the domestic consumer market is not mature LED, LED product advantages and energy-saving ideas need further publicity and guidance, along with the relevant product standards and gradually improve the domestic LED market will usher in rapid growth." Dai Yuanqing said.
LED temperature change of the industry, from the performance of listed companies can also be discerned. Reported data show, A shares of 22 listed companies in the first half of 2014 led street light with solar panel of 11.62 billion yuan, an increase of 32%; total profit of 1.79 billion yuan, an increase of 31%.
However, the Electrical Association also said that while the market prospects, China's LED lighting industry still exists overcapacity, fierce price war, rising costs and a series of issues related to the gradual accumulation of increased market risk, and we must pay attention to the relevant enterprises and departments. From the technical level, although the recent years, increasing research and development of domestic LED enterprise innovation, but compared with international counterparts is still not a small gap.
"Domestic LED enterprise technology still needs to be upgraded, 80-90% of the companies are packaging production, the key chip technology is still controlled by the United States, Japan, South Korea enterprises in the hands." Dai Yuanqing said.
In the 116th Canton Fair lighting exhibition, the reporter saw domestic companies have exhibited a wide variety of LED lighting, some companies develop new products can be manipulated using Bluetooth, a number of new product design novel also won the Fair because of export products design Awards attracted many overseas businessmen to consult.
"This year's LED export situation is very good, stable export markets in developed countries, emerging countries has grown rapidly in the next few years, the domestic market is expected to show explosive growth." LED lighting division, general manager of Shenzhen Mao-Xin Dai Yuanqing electronics company forecast.
Insiders said that the blue LED chips before the invention, can not be applied to the specific white lighting. The emergence of true blue LED into the home, road and landscape outdoor stage large-scale applications, and to subvert the era incandescent and energy-saving lamps, helps to reduce carbon emissions and environmental protection.
Director of the Joint Innovation Center of Guangdong Province semiconductor lighting industry assistant Li Wenyu told reporters that the current rapid development of LED industry, market prospects. Guangdong Province last year, LED exports reached 60 billion yuan, of which the Russian market is growing very fast, the growth rate of 100%.
According to the authoritative estimates, the next 3-5 years, China's LED lighting products exports will remain 40% annual growth, which slowed down the growth rate of the European and American markets, the strong growth in emerging markets.
According to China CCCME, currently Russia, Southeast Asia and the Middle East are our LED lighting products export orders the fastest growing overseas markets.
"At present, the domestic consumer market is not mature LED, LED product advantages and energy-saving ideas need further publicity and guidance, along with the relevant product standards and gradually improve the domestic LED market will usher in rapid growth." Dai Yuanqing said.
LED temperature change of the industry, from the performance of listed companies can also be discerned. Reported data show, A shares of 22 listed companies in the first half of 2014 led street light with solar panel of 11.62 billion yuan, an increase of 32%; total profit of 1.79 billion yuan, an increase of 31%.
However, the Electrical Association also said that while the market prospects, China's LED lighting industry still exists overcapacity, fierce price war, rising costs and a series of issues related to the gradual accumulation of increased market risk, and we must pay attention to the relevant enterprises and departments. From the technical level, although the recent years, increasing research and development of domestic LED enterprise innovation, but compared with international counterparts is still not a small gap.
"Domestic LED enterprise technology still needs to be upgraded, 80-90% of the companies are packaging production, the key chip technology is still controlled by the United States, Japan, South Korea enterprises in the hands." Dai Yuanqing said.
LEDs Are a Diamond's Best Friend
What makes a piece of jewelry stand out from others doesn't just have to do with the four-C's (cut, color, clarity and carat). Sometimes it has everything to do with the way it looks on display. For jewelers, display cases help protect and highlight products. But for many, the cases also hinder consumers from seeing merchandise details that can lead to sales. As grocers and discount retailers have already discovered, led high bay light fixture wholesale technology helps showcase product details, attract consumer attention and reduce energy expenses. Now the LED lighting trend is making its way to the jewelry industry, where one leading jeweler is turning heads--literally--with its recent upgrade to GE's LED lighting for display cases. As one of the largest independent jewelers in the U.S., The Diamond Cellar in Dublin, Ohio, is known for its expertise in service, selection and, now, its innovative approach to showcasing products throughout its multilevel flagship store. By replacing existing display case bulbs with GE's Immersion(R) LED Display Case Lighting, the retailer is able to add sparkle to all facets of merchandise on display, while guiding a consumer's eye throughout the cases to see the wide selection of jewelry in an effort to increase sales.
GE's LED system uses multiple point sources of light to increase visual reflectivity and shine while reducing operating costs. Its reflector design focuses peak light to the center of the case and radiates light out across the case to eliminate shadows and lighting hot spots often found with fluorescent and halogen lighting. It creates a brighter, more uniform look throughout.
Immersion led high bay light for sale uses advanced thermal management for cooler operation and it consumes as little as 7.8 watts per foot while producing higher lux levels per watt of energy used when compared with fluorescent. While halogen systems produce higher lux levels, the Immersion LED Display Case Lighting offers better optical control and nearly 80 percent energy savings, along with a long 50,000-hour rated life to reduce maintenance hassle and costs. The new LED lighting's environmentally responsible design is not only energy efficient, but also RoHS compliant and doesn't contain lead, mercury or glass.
GE's LED system uses multiple point sources of light to increase visual reflectivity and shine while reducing operating costs. Its reflector design focuses peak light to the center of the case and radiates light out across the case to eliminate shadows and lighting hot spots often found with fluorescent and halogen lighting. It creates a brighter, more uniform look throughout.
Immersion led high bay light for sale uses advanced thermal management for cooler operation and it consumes as little as 7.8 watts per foot while producing higher lux levels per watt of energy used when compared with fluorescent. While halogen systems produce higher lux levels, the Immersion LED Display Case Lighting offers better optical control and nearly 80 percent energy savings, along with a long 50,000-hour rated life to reduce maintenance hassle and costs. The new LED lighting's environmentally responsible design is not only energy efficient, but also RoHS compliant and doesn't contain lead, mercury or glass.
Global LED Market to Reach $14.8 Billion by 2015
Global led high bay light supplier is expected to witness rapid growth, led by increasing demand for efficient displays and lighting fixtures along with the rising awareness levels about energy conservation. Though high prices restricted the initial use of LEDs to a small group of applications (which included decorative lighting, exit signs, architectural lighting, and entertainment lighting), the current LED market is relatively broad in terms of end-use applications and encompasses notebook PCs, LCD TVs, residential and commercial lighting, handsets, and signals and displays. Improvements in luminous efficacy and application technologies of LEDs led to their utilization in backlights, landscape lighting, traffic lights, and automobile lights. Due to rising environmental concerns, most of the governments are focusing on phasing out of incandescent lights, replacing them with energy efficient LED lights. Short-term growth is likely to be propelled by the growing popularity of LED TVs and notebooks, while general lighting segment is expected to drive market growth in the long run, as stated by the new market research report on Light Emitting Diode (LED) market. Mobile phones emerged as the leading end-use market with more than 25% share of value sales for 2009, while led high bay light for sale is expected to post the fastest growth in terms of volume sales. The market is also expected to benefit from rapid technological advancements that are expected to bring down the number of chips per box as well as the average selling price of LEDs.
Although the global economic crisis significantly influenced the operations of LED market in 2009 leading to a sales decline in major LED utilizing sectors such as mobile phones, large outdoor displays and automotive, the decline was partly offset by the increasing use of LEDs in segments such as backlights for notebook PCs and LCD televisions, apart from the lighting sector.
Although the global economic crisis significantly influenced the operations of LED market in 2009 leading to a sales decline in major LED utilizing sectors such as mobile phones, large outdoor displays and automotive, the decline was partly offset by the increasing use of LEDs in segments such as backlights for notebook PCs and LCD televisions, apart from the lighting sector.
Launch of innovative LED solutions to personalize homes
Royal Philips Electronics says it is underlining its global leadership in lighting by substantially broadening its portfolio of LED-based lighting solutions which enhance the lives of people at home and in cities. Light + Building - the world’s leading lighting and architecture fair – is providing Philips with a platform to launch additions to its portfolio of complete and innovative LED lighting solutions for consumer and professional applications, including:
• A breakthrough 12 watt led high bay light price as a substitute for a 60 watt light bulb
• LivingAmbiance – a revolutionary approach to mood creation, wirelessly integrating multiple luminaires and lamps in one system for the home
• The Lirio by Philips, Arcitone and Ledino collections of distinctive, high-design consumer luminaires to match modern interiors.
• New solutions and concepts enabling municipalities to create more livable cities through the adoption of LED street lighting
• LED luminaire and control solutions for offices and shops
Philips is introducing a revolutionary concept in home ambiance: LivingAmbiance. Using a simple remote control, LivingAmbiance enables a room to be easily matched to the mood or the occasion, integrating multiple luminaires and lamps wirelessly to generate any desired type of ambient lighting.
LivingAmbience also incorporates Philips’ latest generation of LivingColors, the acclaimed range of consumer luminaires which enable thousands of colors to be chosen at the touch of a button. The new-shape range of LivingColors colored and white light luminaires build on this proposition by adding adjustable and dimmable white light for daily activities as well as offering more possibilities for ambiance creation.
As LED technology opens up the application of architecture and design in home lighting, Philips will introduce a collection of home luminaires at the cutting-edge of contemporary interior design. Three new product families - Lirio by Philips, Arcitone and Ledino - each enable consumers to express themselves by applying the design flexibility of led high bay light manufacturers with bold new forms, materials and finishes.
During 2010 Philips will introduce a new range of outdoor luminaires – CitySoul, CitySpirit, MileWide and StreetStar – all built around LEDGINE, a future-proofed and fully upgradable platform for outdoor luminaires to maintain pace with progressive improvements in LED technologies.
Philips is also exploring the potential of applying LED to help ‘declutter’ city streets increasingly obscured by a variety of elements, including lighting fixtures. Visitors to Light + Building will be able to see a number of proof-of-concept demonstrations in new street lighting designs, including advanced new LED luminaires which rendering lighting virtually invisible during the day, but still ensure bright, white light at night.
• A breakthrough 12 watt led high bay light price as a substitute for a 60 watt light bulb
• LivingAmbiance – a revolutionary approach to mood creation, wirelessly integrating multiple luminaires and lamps in one system for the home
• The Lirio by Philips, Arcitone and Ledino collections of distinctive, high-design consumer luminaires to match modern interiors.
• New solutions and concepts enabling municipalities to create more livable cities through the adoption of LED street lighting
• LED luminaire and control solutions for offices and shops
Philips is introducing a revolutionary concept in home ambiance: LivingAmbiance. Using a simple remote control, LivingAmbiance enables a room to be easily matched to the mood or the occasion, integrating multiple luminaires and lamps wirelessly to generate any desired type of ambient lighting.
LivingAmbience also incorporates Philips’ latest generation of LivingColors, the acclaimed range of consumer luminaires which enable thousands of colors to be chosen at the touch of a button. The new-shape range of LivingColors colored and white light luminaires build on this proposition by adding adjustable and dimmable white light for daily activities as well as offering more possibilities for ambiance creation.
As LED technology opens up the application of architecture and design in home lighting, Philips will introduce a collection of home luminaires at the cutting-edge of contemporary interior design. Three new product families - Lirio by Philips, Arcitone and Ledino - each enable consumers to express themselves by applying the design flexibility of led high bay light manufacturers with bold new forms, materials and finishes.
During 2010 Philips will introduce a new range of outdoor luminaires – CitySoul, CitySpirit, MileWide and StreetStar – all built around LEDGINE, a future-proofed and fully upgradable platform for outdoor luminaires to maintain pace with progressive improvements in LED technologies.
Philips is also exploring the potential of applying LED to help ‘declutter’ city streets increasingly obscured by a variety of elements, including lighting fixtures. Visitors to Light + Building will be able to see a number of proof-of-concept demonstrations in new street lighting designs, including advanced new LED luminaires which rendering lighting virtually invisible during the day, but still ensure bright, white light at night.
Intematix Lighting-Quality LEDs Set New Price-Performance Benchmark
Intematix Corp., a leading innovator in phosphors, LED components and solid state lighting solutions, today announced the introduction of its C1109D that sets a new value benchmark for lighting-quality LEDs. Ranging from 450 lumens at 143 lumens per dollar in cool white, to 345 lumens at 110 lumens per dollar in high color quality warm white, the ceramic-packaged LED is nominally rated at just 4.7 watts. A typical incandescent bulb would require 25 to 30 watts for an equivalent light output. The led street light with solar panel is suited for a wide array of luminaires, especially those demanding maximum operational cost-efficiency, such as street and roadway lighting, garages, gas station canopy, warehouse, and recessed downlights in restaurant, hospitality and other high usage applications.
“Breaking through 1-cent per lumen for a high color quality, warm white LED is precisely what the LED lighting industry needs in order to encourage more rapid adoption of this energy saving technology”
.“Breaking through 1-cent per lumen for a high color quality, warm white LED is precisely what the LED lighting industry needs in order to encourage more rapid adoption of this energy saving technology,” commented Ilkan Cokgor, Director of Business Development, Lighting Products, for Intematix. “While the business case for led street light wholesale in many 24x7 applications can be fairly clear, luminaire manufacturers are still struggling to show a short enough payback for the more common 12x7 applications, as you find on our roadways, in our parking lots and outdoor service environments, and in many downlight applications. With the LED offerings that have been available up to now, in order to make the business-case work, luminaire manufacturers are often forced to consider potentially less capable LEDs that may not deliver a consistent and high quality color over the long term. A quality LED product, at a breakthrough price point, is the solution.” As with other Intematix patented chip-array-on-ceramic LEDs, the C1109D leverages Intematix' widely recognized patent-backed phosphors, with special production techniques, to deliver impressive color quality and highly controlled bin selections. At 4.7 watts, C1109D series delivers 95 lumens per watt (lm/W) from the 5000K correlated color temperature (CCT) cool white version. The 3000K CCT warm white version is a high color rendering implementation (CRI >80) well suited to general purpose lighting. At 9mm x 11mm, the package is compact enough for use in integral replacement lamps, such as R or PAR type bulbs, as well as other types of downlights and recessed fixtures. The C1109D has several advanced design wins in luminaires that have received Energy Star certification.
“Breaking through 1-cent per lumen for a high color quality, warm white LED is precisely what the LED lighting industry needs in order to encourage more rapid adoption of this energy saving technology”
.“Breaking through 1-cent per lumen for a high color quality, warm white LED is precisely what the LED lighting industry needs in order to encourage more rapid adoption of this energy saving technology,” commented Ilkan Cokgor, Director of Business Development, Lighting Products, for Intematix. “While the business case for led street light wholesale in many 24x7 applications can be fairly clear, luminaire manufacturers are still struggling to show a short enough payback for the more common 12x7 applications, as you find on our roadways, in our parking lots and outdoor service environments, and in many downlight applications. With the LED offerings that have been available up to now, in order to make the business-case work, luminaire manufacturers are often forced to consider potentially less capable LEDs that may not deliver a consistent and high quality color over the long term. A quality LED product, at a breakthrough price point, is the solution.” As with other Intematix patented chip-array-on-ceramic LEDs, the C1109D leverages Intematix' widely recognized patent-backed phosphors, with special production techniques, to deliver impressive color quality and highly controlled bin selections. At 4.7 watts, C1109D series delivers 95 lumens per watt (lm/W) from the 5000K correlated color temperature (CCT) cool white version. The 3000K CCT warm white version is a high color rendering implementation (CRI >80) well suited to general purpose lighting. At 9mm x 11mm, the package is compact enough for use in integral replacement lamps, such as R or PAR type bulbs, as well as other types of downlights and recessed fixtures. The C1109D has several advanced design wins in luminaires that have received Energy Star certification.
New alloys key to efficient energy and lighting
A recent advance by Arizona State University researchers in developing nanowires could lead to more efficient photovoltaic cells for generating energy from sunlight, and to better light-emitting diodes (LEDs) that could replace less energy-efficient led street light wholesale bulbs. Electrical engineers Cun-Zheng Ning and Alian Pan are working to improve quaternary alloy semiconductor nanowire materials. Nanowires are tens of nanometers in diameter and tens of microns in length. Quaternary alloys are made of semiconductors with four elements, often made by alloying two or more compound semiconductors. Semiconductors are the material basis for technologies such as solar cells, high-efficiency LEDs for lighting, and for visible and infrared detectors.
One of the most critical parameters of semiconductors that determine the feasibility for these technologies is the band gap. The band gap of a semiconductor determines, for example, if a given wavelength of sun light is absorbed or left unchanged by the semiconductor in a solar cell. Band gap also determines what color of light an LED emits. To make solar cells more efficient, it's necessary to increase the range of band gaps. Ideally, the highest solar cell efficiency is achieved by having a wide range of band gaps that matches the entire solar spectrum, explains Ning, a professor in the School of Electrical, Computer and Energy Engineering, a part of ASU's Ira A. Fulton Schools of Engineering.
In LED lighting applications, he says, more available band gaps means more colors can be emitted, providing more flexibility in color engineering or color rendering of light. For example, different proportions of red, green and blue colors would mix with different white colors. More flexibility would allow white color to be adjusted to suit various situations, or individual preferences. Similarly, Ning says, detection of different colors requires semiconductors of different band gaps. The more band gaps that are available, the more information can be acquired about an object to be detected. Thus, all of these lighting applications can be improved by having semiconductors with a wide range of band gaps. The researchers say the hurdle is that every manmade or naturally occurring semiconductor has only a specific band gap. One standard way to broaden the range of band gaps is to alloy two or more semiconductors. By adjusting the relative proportion of two semiconductors in an alloy, it's possible to develop new band gaps between those of the two semiconductors. But accomplishing this requires a condition called lattice constant matching, which requires similar inter-atomic spaces between two semiconductors to be grown together.
"This is why we cannot grow alloys of arbitrary compositions to achieve arbitrary band gaps," Ning says. "This lack of available band gaps is one of reasons current solar cell efficiency is low, and why we do not have LED lighting colors that can be adjusted for various situations." In recent attempts to grow semiconductor nanowires with "almost" arbitrary band gaps, the research team led by Ning and Pan, an assistant research professor, have used a new approach to produce an extremely wide range of band gaps.
They alloyed two semiconductors, zinc sulfide (ZnS) and cadmium selenide (CdSe) to produce the quaternary semiconductor alloy ZnCdSSe, which produced continuously varying compositions of elements on a single substrate (a material on which a circuit is formed or fabricated). Ning says this the first time a quaternary led street light fixture Manufacturer has been produced in the form of a nanowire or nanoparticle. By controlling the spatial variation of various elements and the temperature of a substrate (called the dual-gradient method), the team produced light emissions that ranged from 350 to 720 nanometers on a single substrate only a few centimeters in size. The color spread across the substrate can be controlled to a large degree, and Ning says he believes this dual-gradient method can be more generally applied to produce other alloy semiconductors or expand the band gap range of these alloys. To explore the use of quaternary alloy materials for making photovoltaic cells more efficient, his team has developed a lateral multi-cell design combined with a dispersive concentrator.
One of the most critical parameters of semiconductors that determine the feasibility for these technologies is the band gap. The band gap of a semiconductor determines, for example, if a given wavelength of sun light is absorbed or left unchanged by the semiconductor in a solar cell. Band gap also determines what color of light an LED emits. To make solar cells more efficient, it's necessary to increase the range of band gaps. Ideally, the highest solar cell efficiency is achieved by having a wide range of band gaps that matches the entire solar spectrum, explains Ning, a professor in the School of Electrical, Computer and Energy Engineering, a part of ASU's Ira A. Fulton Schools of Engineering.
In LED lighting applications, he says, more available band gaps means more colors can be emitted, providing more flexibility in color engineering or color rendering of light. For example, different proportions of red, green and blue colors would mix with different white colors. More flexibility would allow white color to be adjusted to suit various situations, or individual preferences. Similarly, Ning says, detection of different colors requires semiconductors of different band gaps. The more band gaps that are available, the more information can be acquired about an object to be detected. Thus, all of these lighting applications can be improved by having semiconductors with a wide range of band gaps. The researchers say the hurdle is that every manmade or naturally occurring semiconductor has only a specific band gap. One standard way to broaden the range of band gaps is to alloy two or more semiconductors. By adjusting the relative proportion of two semiconductors in an alloy, it's possible to develop new band gaps between those of the two semiconductors. But accomplishing this requires a condition called lattice constant matching, which requires similar inter-atomic spaces between two semiconductors to be grown together.
"This is why we cannot grow alloys of arbitrary compositions to achieve arbitrary band gaps," Ning says. "This lack of available band gaps is one of reasons current solar cell efficiency is low, and why we do not have LED lighting colors that can be adjusted for various situations." In recent attempts to grow semiconductor nanowires with "almost" arbitrary band gaps, the research team led by Ning and Pan, an assistant research professor, have used a new approach to produce an extremely wide range of band gaps.
They alloyed two semiconductors, zinc sulfide (ZnS) and cadmium selenide (CdSe) to produce the quaternary semiconductor alloy ZnCdSSe, which produced continuously varying compositions of elements on a single substrate (a material on which a circuit is formed or fabricated). Ning says this the first time a quaternary led street light fixture Manufacturer has been produced in the form of a nanowire or nanoparticle. By controlling the spatial variation of various elements and the temperature of a substrate (called the dual-gradient method), the team produced light emissions that ranged from 350 to 720 nanometers on a single substrate only a few centimeters in size. The color spread across the substrate can be controlled to a large degree, and Ning says he believes this dual-gradient method can be more generally applied to produce other alloy semiconductors or expand the band gap range of these alloys. To explore the use of quaternary alloy materials for making photovoltaic cells more efficient, his team has developed a lateral multi-cell design combined with a dispersive concentrator.
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