A lighting and LED reference guide about the basics, the industry and us as consumers
How Do LEDs Work?
On its most basic level, the semiconductor is comprised of two regions. The p-region contains positive electrical charges while the n-region contains negative electrical charges. When Voltage is applied and Current begins to flow, the electrons move across the n region into the p region. The process of an electron moving through the p-n junction releases Energy. The dispersion of this energy produces photons with visible Wavelengths.
When a light-emitting diode is switched on, electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor.
An LED is often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern. LEDs present many advantages over Incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. LEDs are color-controlled monochromatic, narrow bandwidth Lux producing devices. Depending on how the LED chip is packaged determines the beam (narrow or wide) angle. Factors that affect the Beam angles include the shape of the Reflector cup, size of the LED chip, epoxy lens shape, and the distance between the LED chip and the top of the epoxy lens.
For many applications, LED Lamps are superior to incandescent lighting. So why is it that in tens of millions of switches, indicators, control panels, signs, annunciators, displays, decor lights and dozens of other applications, design engineers still specify incandescent technology? It might be that they’re just a few years behind what’s really happening in LED illumination. Unlike incandescent Bulbs that give off the full spectrum of light in a spherical pattern, LEDs emit a focused beam of a single wavelength (color) in only one direction, in a variety of angles. For many applications, such as indicators or switch illuminators, this is not a problem, but it took the development of multi-chip arrays and high-flux LED chips to begin to achieve the effect of an incandescent Filament. Major advancements in LED technology have taken place in recent years such as development of new ‘doping’ technologies that increase LED light output by as much as 20 times over earlier generations, and allow the production of daylight-visible LEDs in virtually any color of the spectrum. In addition to red, yellow, and amber/orange, LEDs are now available in many colors from leaf green to ULtra blue. Even white light, long thought to be an impossibility, is now available in three different shades as a light-emitting diode.
The efficiency of LEDs is most apparent in applications requiring color. Light from a typical incandescent bulb must be filtered so that only light from a particular part of the spectrum (e.g., red, amber or green, etc…) for example—is visible. While LEDs deliver 100 percent of their energy as colored light, incandescent bulbs waste 90 percent or more of their energy in light blocked by the colored lens or filter. Incandescent bulbs also waste 80 percent to 90 percent of their energy on heat generation to reach the temperature for which (Kelvin scale) they are designed. With LEDs you get a more color-controlled monochromatic intense light. Observe the color difference between the third brake light on many modern cars. One third of all third (center brake light) brake lights are red LED clusters.
Many car manufacturers frequently use LEDs because the third brake light is often inaccessible and replacement is essentially impossible. The next time you’re in traffic look for one of these and notice how much more vivid red this light is than that emerging from standard—filtered—incandescent taillights. LEDs are color-controlled monochromatic, narrow bandwidth lux producing devices.
LEDs are available in both visible and infrared wavelengths. Infrared LEDs reach wavelengths of 830 nanometers to 940 nm. Visible colors include red, yellow, orange, amber, green, blue/green, blue, and white. These fall into the spectral wavelength region of 400 nm to 700 nm. The colored light of an LED is determined exclusively by the semiconductor compound used to make the LED chip and independent of the epoxy lens color. Molding different LED chips within a common housing creates multicolor LEDs. Applying positive and negative Voltages turn on each color.
What Parts Make Up An LED?
LED lighting starts with a tiny chip (most commonly about one square millimeter) composed of layers of semi-conducting material. LED packages may contain just one chip or multiple chips, mounted on heat-conducting material called a heat sink and usually enclosed in a lens. The resulting device, typically around 7 to 9 mm on a side, can be used separately or in arrays.
LED devices are mounted on a circuit board, which can be programmed to include lighting controls such as dimming, light sensing and pre-set timing. The circuit board is mounted on another heat sink to manage the heat from all the LEDs in the array. The system is then encased in a lighting fixture, architectural structure, or even a “light Bulb” package.
The basic LED consists of a semiconductor diode chip mounted in the Reflector cup of a lead frame that is connected to electrical (wire bond) wires, then encased in a solid epoxy lens. LEDs emit light when Energy levels change in the semiconductor diode. This shift in energy generates photons, some of which are emitted as light. The specific Wavelength of the light depends on the difference in energy levels as well as the type of semiconductor material used to form the LED chip.
Level 1 – The chip or die
Level 2 – The LED component
Level 3 – LED array; may include optics, heat sink and/or Power supply
Level 4 – LED Luminaire
How Were LEDs Developed?
LED technology was actually invented in 1927, when Oleg Losev published details of the first-ever light-emitting diode in a Russian journal. The first visible-spectrum (red) LED was invented in 1962 by Nick Holonyak at General Electric.
The first commercial LEDs were commonly used as replacements for Incandescent and neon indicator Lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches. Until 1968, visible and infrared LEDs were extremely costly — on the order of US$200 per unit — and so had little practical use.
The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators. Hewlett Packard (HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later, other colors became widely available and appeared in appliances and equipment.
In the 1970s commercially successful LED devices at less than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with the planar process invented by Dr. Jean Hoerni at Fairchild Semiconductor. The combination of planar processing for chip fabrication and innovative packaging methods enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to meet the necessary cost reductions. These methods continue to be used by LED producers.
As LED materials technology grew more advanced, light output rose, while maintaining efficiency and reliability at acceptable levels. The invention and development of the high-Power white-light LED led to use for illumination, which is fast replacing incandescent and fluorescent lighting. Most LEDs were made in the very common 5 mm T1.5 and 3 mm T1 packages, but with rising power output, it has grown increasingly necessary to shed excess heat to maintain reliability, so more complex packages have been adapted for efficient heat dissipation.
Packages for state-of-the-art high-power LEDs bear little resemblance to those of early LEDs. The first experiments with blue LEDs were conducted in the 1970′s by Jacques Pankove (inventor of the gallium nitride LED) at RCA Laboratories, but the initial results were not disappointing. Research related to blue LEDs continued and, in the late 1980′s, some key breakthroughs in GaN epitaxial growth and p-type doping were achieved by Isamu Akasaki and Hiroshi Amano, who worked for the University of Nagoya, in Japan. Following in the footsteps of the two researchers mentioned above, in 1993, Shuji Nakamura of Nichia Corporation of Japan demonstrated the first high-brightness blue LED Based on InGaN. Then, in 1995, Alberto Barbieri from the Cardiff University Laboratory in the United Kingdom investigated the efficiency and reliability of high-brightness LEDs, demonstrating very high results by using a transparent contact made of indium tin oxide (ITO) on (AlGaInP/GaAs) LED.
These developments led to the appearance of the first white LED. The popularity and range of uses of LEDs skyrocketed in the 1990s, as the use of small light-emitting diodes became common in a wide variety of products, not only as light sources but also for LCDs and laptop panels. Nowadays, a LED can be found just about anywhere a light source is present, and by 2020 they will be account for the vast majority of all lighting sources.
How are LEDs manufacturered?
There are seven steps of LED manufacture:
- Other Molding
- Circuit Board Assembly
- Final Assembly
Sapphire Substrate creation Manufacturing of flexible mold for nano printing PC structure imprinting onto substrate Dry etching Epitaxial-layer growth Electrode processing Chip dicing Reflector molding LED chip bonding Wire bonding Encapsulating silicone material Silicon lens molding Lead frame cutting Mounting LED package The following is a series of videos introducing and exploring the processes by which LEDs are manufactured. LED Manufacturing process
LED chip placers
LED chip placers part 2
LED manufacturing from Philips
Chip placement – awesome!
What LED Technologies Exist?
Infrared Original Type Gallium Arsenide (GaAs) A spectral peak at 940 nm makes this LED invisible to the human eye. Voltage drop is 1.2 – 1.3 volts. Drive Current is 50mA.
High-Efficiency Infrared Gallium Aluminum Arsenide (GaAlAs) 880 nm & 940 nm Gallium Aluminum Arsenide accounts for the higher Efficacy as compared to the Gallium Arsenide LED. Also, this LED features a shorter peak Wavelength—880 nm. Voltage drop is around 1.4 volts. Drive current is 50 mA. Because the spectral output extends into the low 800s nm (wavelengths visible to the human eye) this LED is dimly seen in a dark room.
Original High-Efficiency Red (630 nm) 1960 – Gallium Phosphide doped with Zinc & Oxygen (GaP: Zn, O) This LED is efficient (1 to maybe 2 Lumens/Watt) at a few milliamps or less. At 20 mA, it’s about 2 – 3 times as efficient as the original formula visible red LED. Color varies with current. At 0.5 – 1.0 mA the LED output is nearly pure red, at higher currents it appears more orange. If the Lamp is not tinted red, the emitted light color ranges from orange to yellowish-orange at 30 mA. Spectral output is a broad band, nominally peaking at 697 nm and maybe only peaking that far out in the red at really low currents. At higher currents, there is a very weak secondary spectral band in the blue-green band around 510 nm. Maximum drive current is usually 30 mA, but this LED has a noticeably nonlinear light output that increases less than proportionately with current above a few milliamps. Voltage Drop is around 1.9 volts.
Original-Formula Visible Red 1968 – Gallium Arsenide Phosphide (GaAsP) on a Gallium Arsenide (GaAs) Substrate Spectral output peaks around 660 nm. Color is a pure red. Efficacy is low. Most LEDs using this technology need a maximum continuous drive current of 50 mA, but at a typical current of 20 mA it is reasonably bright. Efficacy is maximized at currents of 20 mA and up. Voltage drop is 1.6 – 1.75 volts.
ULtra Brightness Red (660 nm) 1980 – Gallium Aluminum Arsenide Phosphide (GaAlAsP) Overall Luminous Efficacy of this LED is, at best, 9 lumens/watt. Output peaks between 650 nm and 670 nm. Color is pure red to laser red with a dominant wavelength (monochromatic light of matching color) in the 640s but can range from about 635 to about 650 nm. Efficacy maximizes at currents near 20 – 25 mA. Voltage drop at 20 mA is 1.8 to 1.9 volts. Maximum rated drive current is 30 mA but sometimes 50 mA. Dimly glows at 1.5 volts.
High-Efficiency Red, and Orange 1990 – Gallium Arsenide Phosphide (GaAsP) on Gallium Phosphide (GaP) substrate This was the first non-low-current, high-efficiency red LED. The Gallium Phosphide substrate is transparent to the emitted light and Gallium Arsenide is not. This is one reason why this LED is more efficient than the original-formula red. Color is orange-red with a dominant wavelength around 620 nm. A slight variation of this has a dominant wavelength usually around 610 – 615 nm and is considered orange. Drive current is 5 – 20 mA. Maximum current is 30 mA. Voltage drop at 20 mA is around 1.9 volts.
What Is The Future For LEDs?
Compact fluorescent (CFL) Bulbs are only a temporary solution to Energy-efficient lighting; LED light bulbs will eventually be what we use to replace Incandescent bulbs. LEDs have not yet displaced CFLs from the market because the first generation LED bulbs had a narrow and focused light beam, and the cost of the LED bulbs was too high.
Recent developments in LED technology, however, have been addressing these issues. LEDs have been ‘clustered’ to provide more light, and mounted within diffuser lenses which spread the light across a wider area. And advancements in manufacturing technology have driven the prices down to a level where LED bulbs are more cost-effective than CFLs or incandescent bulbs. This trend is continuing, with LED bulbs being designed for more applications while the prices are going down over time.
The ‘sticker shock’ of the new LEDs remains a deterrent to their widespread acceptance by consumers. However, the latest LED bulbs when compared with CFLs and incandescents for overall efficiency as well as cost-effectiveness. The LED lighting industry is set to dominate the global market more than a century after its discovery, benefitting from a widespread ban of conventional incandescent bulbs and as the market share of competing green replacements fade. Light emitting diodes (LEDs) have a vital edge in that they have superior energy efficiency and longer lifespans compared with rivals, while a global glut in LED chips means they are becoming more competitive. A forecast explosion in LED sales by more than 40 percent annually will see the technology eclipse high-efficiency rivals such as compact Fluorescent Lamps (CFLs). Meanwhile, the main LED market challenge of high upfront costs is eroding. And, while concerns remain of a potential manufacturing bubble stemming from a boom-bust cycle of over-capacity – which has been seen in other clean energy technologies sectors such as wind and solar – freedom from subsidy programmes may see demand rise more smoothly than with fickle government support.
There are 4 main areas that directly affect the ROI in regards to LED lighting, Market share, laws banning old inefficient lighting, the final edge of life for old light bulb production & payback timeframe regarding quality of 1st and second generation LED bulbs. In general terms, LED lighting ROI is 18-24 months.
LEDs will surge in the U.S. lighting market, to a 36 percent share in 2020 and 74 percent in 2030, a U.S. Department of Energy report forecast last year, implying $30 billion in annual energy savings by 2030. The study, “Energy Savings Potential of Solid-state lighting in General Illumination Applications”, forecast rapid gains after 2014 as prices continue to fall. Predictions are even more aggressive for the global 55 billion euro ($71.86 billion) General Lighting market (which excludes automotive and specialist backlighting), forecasting a 45 percent LED market share in 2016 from 9 percent in 2011. LEDs would usurp traditional efficient light bulbs such as CFLs, the consultants said in their “Perspectives on the global lighting market” study in August.
Developed countries are banning incandescent light bulbs on the basis that they are inefficient and contribute to global warming and energy insecurity, while governments chase building efficiency programmes. The International Energy Agency reported that 26 of its 28 member countries had policies in place to phase out incandescent bulbs as of 2011, except in New Zealand and Turkey. The European Union (19 EU countries are IEA members) last year phased out all non-directional, clear incandescent light bulbs usually used in household illumination. The United States banned 100-Watt incandescent light bulbs from October last year, followed by 75-watt bulbs this month and with 60-watt bulbs to follow. Among emerging economies, China said it would ban 100-watt incandescents from October last year, with other varieties following through 2016.
Incandescent light bulbs produce light when an electric Current runs through a wire inside the bulb’s glass globe, causing the wire to heat up and glow. Halogen lamps are similar but add a gas which extends the product lifespan and allows them to operate at higher temperatures. LEDs generate light when electricity flows through an electronic component called a diode. CFLs and fluorescent tubes emit light when electricity excites a mix of gases inside the bulb, creating invisible ULtraviolet light that is absorbed by the bulb’s fluorescent coating and transformed into visible light.
LEDs will become dominant in the wake of the incandescent ban, but it is actually an old technology. Britain’s H.J. Round is credited with being the first person to publish the light emitting diode effect, in 1907. Modern LEDs are superior to CFLs in terms of total environmental impact including the energy and natural resources needed to manufacture, transport, operate and dispose of light bulbs, concluded a report published in September by the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL) and UK-Based N14 Energy Limited. It compared the most typical and widely available light bulb in each technology class: LEDs, CFLs and incandescents. With regards to operating efficiency, LEDs and CFLs were neck and neck: the bulbs each created about the same amount of light (800-900 Lumens) but the incandescent bulb consumed 60 watts of electricity, followed by the CFL’s 15 watts and LED’s 12.5 watts. But LEDs beat CFLs on overall environmental performance, including the energy and resources needed to make them.