Light-emitting diode

Small parts can make light.

They use power to glow. This happens when electricity flows through them.

These lights can be many colors. Some are red, green, or blue. To make white light, they mix colors together.

We use these lights every day. You might see them in traffic lights.

They are also in fairy lights.

These lights are very good. They do not use much power. They also last a long time.

It is fun to see them shine!

An LED is a tiny part that makes light.

It uses a material called a semiconductor. When electricity flows through it, light comes out.

This happens because tiny parts called electrons move. They join with "holes" in the material. This act lets out energy as light. This way of making light is called electroluminescence.

The color of the light depends on the material. Some LEDs make red, green, or blue light. To make white light, we use two main ways. One way is to mix red, green, and blue light.

The other way uses a coating called phosphor. This coating changes blue light into white light.

LEDs are very useful. They use less power than old bulbs. They also last a long time. You can find them in traffic signals.

They are in car headlights and even fairy lights. They are even used to help plants grow.

A light-emitting diode, or LED, is a tiny electronic part that makes light.

It works by turning electricity into light. This makes LEDs very useful for many things. They are much better than old light bulbs in several ways. They use less power to work. They also last a long time and are very tough.

You can find them in car headlights, traffic signals, and even fairy lights.

Inside an LED, there is a material called a semiconductor. When electricity flows through it, a special thing happens. Tiny parts called electrons move and join with "holes" in the material. This process is called electroluminescence.

When they join together, they release energy as light particles called photons. The color of the light depends on how much energy is released. This energy is tied to something called a band gap. A larger gap creates higher energy light, like blue or ultraviolet. A smaller gap creates lower energy light, like red or infrared.

People have been studying this for a long time. In 1906, Henry Joseph Round discovered this effect at Marconi Labs. He saw crystals emit different colors when electricity passed through them.

Later, in 1927, Oleg Losev made a silicon carbide LED. Real, useful LEDs arrived in 1962 from Texas Instruments engineers. At first, they were very expensive to make. By the 1970s, companies like Monsanto and Hewlett-Packard made them much cheaper.

Making white light was a big step for science. In the early 1990s, Shuji Nakamura, Hiroshi Amano, and Isamu Akasaki created blue LEDs. This work won them the Nobel Prize in Physics in 2014.

Blue light is needed to make white light. One way to make white light is to mix red, green, and blue LEDs.

Another common way uses a phosphor coating. This coating takes blue light and turns it into white light.

This method is used in many common light bulbs today.

LEDs are used in many parts of our daily lives. They are in the screens of many electronic devices.

They are used in aviation lighting and medical devices too. Some special UV LEDs are even used to check bank notes for fake marks.

They can even help plants grow in special lights.

While they are great, they do need specific types of power. They usually need low voltage and DC power to work best.

A light-emitting diode, or LED, is a specialized electronic component. It uses a semiconductor material to convert electricity into light. This process is known as electroluminescence.

LEDs are essential in modern technology because they are highly efficient. They consume much less power than traditional incandescent bulbs. They also offer longer lifetimes and improved physical robustness.

Because they are small and switch on and off very quickly, they are used in everything from tiny sensors to massive displays.

The physics of an LED relies on the movement of subatomic particles. Inside the semiconductor, electricity causes electrons to move. As these electrons flow, they recombine with "electron holes."

This recombination releases energy in the form of photons, which are particles of light. The specific color of the light depends on the energy of these photons. This energy is determined by the semiconductor's band gap. The band gap is the energy required for electrons to cross a specific barrier within the material.

A larger band gap produces high-energy light, such as blue or ultraviolet. A smaller band gap produces lower-energy light, such as red or infrared.

Engineers can create different types of single-color LEDs by selecting specific semiconductor materials. Blue LEDs often use Indium Gallium Nitride (InGaN) quantum wells. These wells are sandwiched between thicker layers called cladding layers.

By changing the ratio of Indium to Gallium, the light color can shift from violet to amber. Ultraviolet LEDs can be made using Aluminium Gallium Nitride (AlGaN). Some specialized UV LEDs emit light at 250–270 nm. This specific wavelength is useful because it matches the absorption spectrum of DNA. Such devices are being researched for future disinfection and sterilization uses.

Producing white light is more complex than producing a single color. There are two primary methods to achieve this. The first method uses an RGB system. This system mixes individual red, green, and blue LEDs to create white light.

This method allows for great color flexibility. However, it requires complex electronic circuits to control the blending. The second, more common method uses a phosphor coating. In this setup, a blue or ultraviolet LED shines on a phosphor material.

The phosphor converts the monochromatic light into a broad-spectrum white light. For example, many white LEDs use cerium-doped YAG crystals. These crystals appear yellow when the LED is turned off.

The history of the LED is a journey of many decades. Henry Joseph Round first discovered electroluminescence in a solid-state diode in 1906. He observed carborundum crystals emitting various colors when voltage was applied.

In 1927, Soviet inventor Oleg Losev created a silicon carbide LED. However, commercially viable LEDs did not arrive until 1962. That year, Texas Instruments engineers patented an efficient near-infrared emission. While early LEDs were expensive, companies like Monsanto and Hewlett-Packard reduced costs significantly by the 1970s. A major breakthrough occurred in the early 1990s. Shuji Nakamura, Hiroshi Amano, and Isamu Akasaki developed blue LEDs. This discovery made full-color displays and white lighting possible. They were awarded the Nobel Prize in Physics in 2014.

LEDs are used in a massive variety of applications today. You can find them in automotive headlamps and traffic signals.

They are used in aviation lighting, stage lighting, and camera flashes. Even specialized horticultural grow lights use LEDs to help plants.

They are also found in medical devices and advertising displays.

Despite their many benefits, LEDs have specific limitations. They generally require low voltage and direct current (DC) power. They cannot provide steady light from an alternating current (AC) source without a power supply. They also have lower maximum operating and storage temperatures than some other components.

Understanding LEDs helps us see how light technology is evolving. The field involves complex trade-offs between efficiency and color quality. For instance, some white LEDs have high luminous efficacy but low color rendering. This means they use very little power but may not show colors accurately.

Other LEDs prioritize color rendering, making them better for high-quality lighting. As research continues, scientists aim to improve the efficiency of green LEDs. Currently, the blue and red LEDs are much closer to their theoretical maximum efficiency. This ongoing development connects semiconductor physics to the way we illuminate our entire world.