What is LED (Light-Emitting Diode)?

An LED (Light-Emitting Diode) is a semiconductor device that emits low spectrum inconsistent light when the PN joint is directly polarized and an electric current passes through it.

What is LED (Light-Emitting Diode)?

What is LED Features and Working Principle, How Does It Work?

The color depends on the semiconductor material used to make the diode, and it can vary from ultraviolet to visible to infrared.

Ultraviolet diodes are called UV (Ultraviolet Light) and infrared light-emitting diodes are called IRED (InfraRed Emitting Diode).


The first led was developed by Oleg Vladimirovich Losev in 1927, but it was not used in the industry until the 1960s.

The LEDs had only low light intensity in red, green, and yellow, and it was possible to manage them on and off with the remote control.

At the end of the 20th century, ultraviolet and blue LEDs were invented, which led to the development of white led, a phosphor-coated blue light led that produces yellow light.

White led is like moonlight that provides high brightness, which expands the use of lighting systems.

How Does It Work?

The operation of the LEDs consists of the loss of energy of an electron in the semiconductor materials, passing from the transmission band to the valence band.

This lost energy can occur as a displaced photon with random amplitude, direction, and phase.

Whether the energy lost when an electron passes from the conduction band to the valence band will depend primarily on the type of semiconductor material, whether it will emerge as an independent photon or another form of energy.

When a semiconductor diode is directly biased, the p region holes move to the n region and the n region electrons to the p region.

Both displacements of the loads form the current passing through the diode.

If electrons and holes are in the same region, they can reunite, that is, electrons hold holes that fall from a higher energy level to a more stable lower level.

This process generally emits a photon indirect bandgap or direct bandgap semiconductors with energy corresponding to the bandgap.

This does not mean that there is no photon emission in other semiconductors.

However, these emissions are more likely than indirect bandwidth semiconductors compared to indirect bandwidth semiconductors.

Therefore, self-emission does not occur prominently in all diodes and can only be seen in diodes like visible light LEDs.

It has a special constructive arrangement and the energy of the banned band corresponding to the visible spectrum to prevent the radiation from being reabsorbed by the surrounding material.

In other diodes, energy is primarily released in the form of heat, infrared radiation, or ultraviolet radiation.

If the diode releases energy in the form of ultraviolet radiation, it absorbs ultraviolet radiation emitted by the diode.

It then produces visible radiation by means of fluorescent or phosphorous substances that emit visible light.

The semiconductor device is encapsulated in a more durable plastic cover than the glass used in incandescent lamps. Although plastic can be colored, it does not affect the color of the emitted light.

This is usually a composite light source with different parts, so the intensity pattern of the emitted light is quite complicated.

To get a good light intensity, the led current should be chosen well.

For this, it should be taken into account that the operating voltage varies from about 1.8 to 3.8 volts and varies according to the application of the current range that must circulate.

Typical values ​​of the direct polarization current of the current are between 10 and 40 mA.

In general, LEDs have better efficiency. Therefore, the lower the current through it, a compromise occurs between the light intensity and efficiency they typically produce in their optimized operation.

The first LED emitted in the visible spectrum was developed in 1962 by General Electrical engineer Nick Holonyak.

OLED Technology

In direct current (DC), all the diodes emit a certain amount of radiation when the electron-hole pairs reunite.

In short, when electrons fall from the transmission band to the valence band, they emit photons in the process. As a result, its color will depend on the height of the tape, that is, the materials used.

Silicon or germanium diodes emit far-infrared radiation far from the visible spectrum. However, with special materials, visible wavelengths can be achieved.

LEDs and IREDs have special geometries to prevent the emitted radiation from being reabsorbed by the surrounding material.

The first diodes discovered were red-colored and infrared diodes and more advanced technological advances that allowed the making of diodes.

In particular, in the late 1990s, Shuji Nakamura developed blue diodes. By adding reds and greens to the previously developed combinations, they added white light.

Zinc selenide diode can also emit white light by mixing the blue light it emits with red and green light created by photoluminescence.

The latest innovation in the field of LED technology is ultraviolet diodes, which have been successfully used in the production of black light to illuminate fluorescent materials.

Both blue and ultraviolet diodes are expensive compared to the most common and are therefore less used in commercial applications. Typical commercial LEDs are designed to be 30 to 60 mW of power.

In 1999, diodes capable of operating at 1 watt for continuous or daily use were introduced to the market.

These diodes have much larger semiconductor matrices to withstand such powers and include metal fins to dissipate heat generated by the Joule effect.

Today, LEDs are being developed and used in various fields with much higher performance and lighting applications.

Using 20 milliamps (mA) direct polarization current from Nichia Corporation, it developed white light LEDs with a luminous efficiency of 150 lm/W.

This efficiency is only 1.7 times higher than a high color and fluorescent lamp and 11.5 times higher than an incandescent lamp compared to other light sources in terms of performance only.

Its efficiency is even higher than that of the high-pressure sodium vapor lamp, which is considered one of the most efficient light sources.

At the beginning of the 21st century, the development of OLED diodes made of organic semiconductor polymer materials began.

Although the efficiency obtained with these devices is far from inorganic diodes, their production aims to be much cheaper than themselves.

It is also possible to add large amounts of diodes to any surface using painting techniques to create color screens.

OLED is a diode based on an electroluminescent layer created by a film of organic components that reacts to a specific electrical stimulation that automatically generates and emits light.

OLED-based technologies do not just have an application as image replication screens.

The advantages of this new technology are enormous, but many of them have a number of disadvantages, although they are purely situational.

Hybrid Lighting Systems are a technological solution that aims to take advantage of the high efficiency of typical LEDs and the low costs of OLEDs.

Two examples of such a technological solution are designed by Cyberlux under the name HWL (Hybrid White Light) and HML (Hybrid Multi-Color Light). As a result of these studies, it can produce much more efficient and cost-effective lighting systems.

Where is the LED used?

Infrared diodes have been used in remote control of television systems, air conditioning equipment, music equipment, all remote control applications, and device detectors since the mid-20th century.

It is also used for data transmission between electronic devices such as computer networks and devices such as mobile phones and handheld computers. Although this data transmission technology is older than Bluetooth technology, it can still be used today.

LEDs are widely used in all kinds of status indicators in signal devices and information panels.

They are also used in the lighting of liquid crystal displays for mobile phones, calculators, electronic logs, bicycles, and similar uses.

In addition, it is also used in laser printers, which are frequently used in conjunction with office applications, and that serve as documentation.

LED lighting has excellent advantages. These; It has many advantages such as reliability, more energy efficiency, more resistance to vibrations, better visibility in different lighting conditions, less energy distribution, less risk to the environment, ability to work continuously.

LEDs, unlike most of the lamps used so far, can produce different colored lights with high luminous efficiency with filters to achieve a similar effect.

White Light LEDs are a very well established initiative to replace existing bulbs with much more advantageous devices.

Today, technology is available that consumes 90% less than common domestic incandescent bulbs and 40% less than most fluorescent lamps.

Also, they can last up to 20 years and cost less than traditional fluorescent bulbs.

It is also used in the emission of light signals transmitted over fiber optics.

The LED display is a very bright display, consisting of green, blue, and red rows, individually controlled to create very bright and very high contrast vivid images, arranged according to the RGB architecture.

It gives good color support, extremely high brightness, ability to be fully visible in sunlight compared to others on LED displays.

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