How does led lighting work

The boundary between the two types is called a p-n junction. The junction only allows current to pass through it one way, this is why they are used as diodes. LEDs are made using p-n junctions. As electrons pass through one crystal to the other they fill electron holes. They emit photons light. This is also how the semiconductor laser works. Above: A laser also creates light, but through a different construction. Read more about semiconductor devices used in electronics here.

To understand p-n junctions and semiconductors better you will need to invest a good amount of time in a lecture, it is not a simple phenomena and far too lengthy to cover here. See a 59 minute introduction lecture to solid state semiconductors here. Phosphors are used to help filter the light output of the LED.

They create a more pure "harsh" color. Engineers had to figure out how to control the angle the light escapes the semiconductor, this "light cone" is very narrow. They figured out how to make light refract or bounce off all surfaces of the semiconductor crystal to intensify the light output. This is why LED displays traditionally have been best viewed from one angle.

The metal tabs on the sides of each help distribute the heat away from the LED. Photo: Whelan Communications. This type of display is only usable for large area applications and decorative backgrounds in small spaces.

The human eye can only effectively perceive the image at more than 6 meters distance. The tricolor array is arranged in the close-up at the top right. There are also orange, green, blue, violet, purple, ultraviolet LEDs.

For more details on elements used for each color go here. Above: Two different types of LEDs, both in a strip mount configuration. Above: this experiment of a tunnel diode atop a GaAs semi-insulating substrate convinced Pittman and Biard that there must be light emission going on, and resulted in further experimentation.

The early years of the s consisted of a 'race' in the field of semiconductors. Gallium arsenide and germanium were some of the first semiconductors uses before silicon became the preferred material in the industry. These devices were being developed as diodes since they can pass current in one direction by not the other.

Biard and Gary Pittman. Gary had been working in the related field of solar cells since In their efforts to try to make an X-band GaAs varactor diode they created tunnel diodes which had been developed first at Esaki.

They placed the tunnel diode on a GaAs substrate and discovered that there must be light production going on during forward bias operation. Using an infrared detector just brought in from Japan they tested it and discovered that the devices lit up brightly! The LEDs were first used with IBM computers to replace tungsten bulbs that controlled punch card readers infrared light was sent through the holes, or blocked by the card.

Today there is a myriad of applications for the LED. The First LED patent click to enlarge. Above: Walter T. Matzen top and Bob Biard bottom worked on parametric amplifiers, this helped lay groundwork for the LED.

Later Gary Pittman and Mr. Biard worked on varactor diodes which led to the LED as we know it. Read the full story of their work with this PDF here. Round discovered electroluminescence when using silicon carbide and a cats whisker. Oleg Losev independently discovered the phenomena the same year.

London, United Kingdom. So, an LED bulb was traditionally dimmer than an incandescent bulb, and most people want their lamps and ceiling fixtures to be pretty bright. Now, LEDs bulbs have brightened up. You can now find LED replacement bulbs that emit light equivalent to a watt incandescent light bulb or higher, which makes them a viable technology for basic lighting needs at home.

And a LED replacement light bulb has a life 24, hours longer than that of a traditional incandescent watt bulb. And it's cheaper. First, there's the reduced energy use. The LED method of producing light uses far less energy to heat than do other lighting technologies. But energy efficiency is just part of the story. The other part is time efficiency: A good-quality LED bulb theoretically can have a life span of 25, hours or more , while incandescent bulbs have a 1,hour life span.

Solid-state lights like LEDs are more stable light sources than incandescent or fluorescent bulbs, and the difference is startling: You'd have to leave a LED light on for 24 hours a day, seven days a week for three years before it matches an incandescent bulb's life span.

In fairness, not all LED light bulbs last as long as they can in theory. Some may have shorter life spans if parts wear out prematurely.

Because of that time benefit, things get a bit more muddled when you get into the cost issue. LEDs are poised to take over household lighting. It's estimated that LEDs will account for 75 percent of all lighting sales by If you look at what the scientists are saying about LEDs, the picture does look pretty rosy. Breakthroughs are popping up at a breakneck pace. Except there's one problem. A growing number of studies have come out about the blue light that LEDs emit.

There are only 8, hours in a whole year — imagine how long an LED bulb would last in the average home! That makes LEDs sound pretty great — and they are — but there are reasons incandescent and compact fluorescent bulbs are still around. The biggest reason is price; LED bulbs cost more than the other options, even though prices for LED bulbs have come down in recent years. However, their longer life spans and dramatically lower power usage help make up for the higher barrier of entry.

In addition to the high cost barrier, LEDs are vulnerable to high temperatures. If LED circuitry gets too hot, more current will pass through the junction mentioned earlier in this article.

When the junction gets too hot, it causes the bulb to burn out [source: LEDs Magazine ]. And even though LEDs are free of mercury unlike CFL bulbs , they may contain other dangerous elements such as lead or arsenic [source: Scheer and Moss ].

Further, one study found light pollution increased with the use of LED bulbs [source: Brady ]. Some people also prefer the look of incandescent light, feeling they're warmer than the yellowish-looking CFL bulbs and the bluish brightness of LEDs.

The difference in lighting types can take some adjustment, but LEDs are also available in a variety of hues. LEDs are dimmable unlike CFLs and are perfect for encouraging plant growth, since they efficiently put off tons of light without producing heat that could potentially be damaging to plant life. While CFLs and incandescent bulbs are limited to the color of their enclosure, some LED bulbs can be changed to emit millions of colors.

These bulbs are typically more expensive than their white LED bulb counterparts, but they can be programmed to change color with the time of day, giving people more control over their environment. LEDs have come a long way since the early days of lighting up digital clock faces.

LCD displays were even a major step above HD rear-projection sets that weighed well over pounds But LED technology changed the market. While LCD TVs were far thinner and lighter than massive rear-projection sets, they still used cold cathode fluorescent tubes to project a white light onto the pixels that make up the screen.

Those add weight and thickness to the TV set. LEDs solved both problems. Have you ever seen a gigantic flat-screen TV barely an inch thick? It was probably an LED television. Instead of fluorescent tubes, LEDs shine light from behind the screen, illuminating the pixels to create an image. They can also provide a wider color gamut, producing more vivid pictures. There are several different types of LED-backlit sets are on the market — and not all are created equal. Many sets use white LED edge lighting to shine light across the display.

The only real advantage afforded by these sets is thinness. Some configurations even allow for a technique called local dimming , where LEDs in different parts of the display can be brightened or dimmed independently to create a more dynamic picture [source: Morrison ]. Since the white fluorescent lamps have to remain on during TV use, some light tends to bleed through and lighten the picture in dark scenes.

The organic materials used to create these semiconductors are flexible, allowing scientists to create bendable lights and displays — some manufacturers have already started producing smartphones and other devices that use smaller OLED screens.

As the technology allows better and larger displays, you may start seeing them in places you would never have been able to find a screen before. OLEDs also allow individual pixels to be turned completely off, letting viewers see true black. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Need help? Just contact us via chat, email, phone, or pop in and see us.

We'll find the perfect bulb for you. You can simply replace your existing lamps or upgrade to the latest versions if you're feeling green. Log in. February 10, Posted by Sarah Levison. What is an LED? Indicator — an inexpensive, low-power device that is used as indicator lights in cars, panels, and other electronic devices. Illuminator — a high-power device that provides illumination. These are the type of LEDs you buy to illuminate rooms in your home or office.