What makes leds function

The boom of white bulbs, which are the most used and sought-for ones, came when the blue saltpeter was combined with yellow luminophore to produce long wavelengths. The result of this combination is the light that the human eye perceives as white. Structurally, Light-Emitting Diode LED represents a component in which the contacted chip or combination of chips is sprayed with a material with the desired optical properties LEDs are produced in point or diffuse design, with different beam angles.

The contacts can be surface mounted SMD or flexible or flexible. Multiple LED chip assemblies in a single housing can have separate contacts for each chip, common anode or cathode, or antiparallel, or they can have control electronics on the chip for example, color-changing or flashing LEDs.

The basic single-crystal diodes are usually covered with spherical caps made of epoxy resin or acrylic polyester. Indeed, the materials from which LEDs are made have a relatively high refractive index and a large part of the light emitted would be reflected by total reflection back at the planar interface with the air.

Compared to other electrical light sources bulb, discharge lamp, glow lamp , LEDs have the advantage of working with relatively low current and voltage values. This implies their use in displays in the form of digits and letters. By combining the base colors red, green, blue it is also possible to obtain color screens. Four main advantages of this lighting have to be mention here: it is the energy efficiency, the light efficiency, its ability to light at full intensity immediately after switching on and its lifetime.

The greatest advantage of LED lamps over the incandescent ones is noticeably lower power consumption. A suitable measure for energy efficiency is the luminous efficiency, which means how great a luminous flux is emitted by a light source at 1 Watt. Thus, the LED bulb is about ten times as efficient as the standard incandescent one. To get rid of the depletion zone, you have to get electrons moving from the N-type area to the P-type area and holes moving in the reverse direction.

To do this, you connect the N-type side of the diode to the negative end of a circuit and the P-type side to the positive end. The free electrons in the N-type material are repelled by the negative electrode and drawn to the positive electrode. The holes in the P-type material move the other way. When the voltage difference between the electrodes is high enough, the electrons in the depletion zone are boosted out of their holes and begin moving freely again.

The depletion zone disappears, and charge moves across the diode. If you try to run current the other way, with the P-type side connected to the negative end of the circuit and the N-type side connected to the positive end, current will not flow.

The negative electrons in the N-type material are attracted to the positive electrode. The positive holes in the P-type material are attracted to the negative electrode. No current flows across the junction because the holes and the electrons are each moving in the wrong direction.

The depletion zone increases. See How Semiconductors Work for more information on the entire process. The interaction between electrons and holes in this setup has an interesting side effect — it generates light!

Light is a form of energy that can be released by an atom. It's made up of many small particle-like packets that have energy and momentum but no mass. These particles, called photons , are the most basic units of light. Photons are released as a result of moving electrons. In an atom, electrons move in orbitals around the nucleus. Electrons in different orbitals have different amounts of energy. Generally speaking, electrons with greater energy move in orbitals farther away from the nucleus.

For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level. Conversely, an electron releases energy when it drops from a higher orbital to a lower one. This energy is released in the form of a photon.

A greater energy drop releases a higher-energy photon, which is characterized by a higher frequency. As we saw earlier, free electrons moving across a diode can fall into empty holes from the P-type layer. This involves a drop from the conduction band to a lower orbital, so the electrons release energy in the form of photons. This happens in any diode, but you can only see the photons when the diode is composed of certain material.

The atoms in a standard silicon diode, for example, are arranged in such a way that the electron drops a relatively short distance. As a result, the photon's frequency is so low that it's invisible to the human eye — it's in the infrared portion of the light spectrum. This isn't necessarily a bad thing, of course: Infrared LEDs are ideal for remote controls , among other things. Visible light-emitting diodes VLEDs , such as the ones that light up numbers in a digital clock, are made of materials characterized by a wider gap between the conduction band and the lower orbitals.

The size of the gap determines the frequency of the photon — in other words, it determines the color of the light. While LEDs are used in everything from remote controls to the digital displays on electronics, visible LEDs are popular thanks to their long lifetimes and miniature size.

Depending on the materials used in LEDs, they can be built to shine in infrared, ultraviolet, and all the colors of the visible spectrum in between. While all diodes release light, most don't do it very effectively.

In an ordinary diode, the semiconductor material itself ends up absorbing a lot of the light energy. LEDs are specially constructed to release a large number of photons outward.

Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction. Most of the light from the diode bounces off the sides of the bulb, traveling on through the rounded end. For decades, watt incandescent light bulbs have lit up hallways and bedrooms; watt incandescents have shone softer light from reading lamps and closets.

But incandescent lights are inefficient, waste lots of energy as heat, and have shorter lifespans than fluorescent lamps. Recently, more-efficient compact fluorescent CFL bulbs have become popular alternatives. Where incandescent lights last an average of around 1, hours, CFLs can last 10, hours [source: EarthEasy ].

Unfortunately, CFLs contain toxic mercury that makes them potentially hazardous and a pain to dispose of. Enter the LED light bulb. LEDs offer the advantages of CFLs — lower power consumption and longer lifetimes — without the downside of toxic mercury [source: Scheer and Moss ].

LED bulbs are even better, drawing about 8. 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. Depending on its composition, the plastic lens distributes the light in the room accordingly.

In addition, the plastic composite makes the LED insensitive to shocks and vibrations. The wavelength of the emitted light can be determined very precisely by doping the semiconductor material.

Depending on the application, LEDs can be produced with different light colors and color temperatures. Due to the narrow wavelength range, no other radiation in the infrared or UV range is generated. The basic LED functionality and its structure has been described before. There are still different subtypes of light emitting diodes. The abbreviation SMD stands for surface mounted device. With this design, the housing also serves as a heat sink for the LED chip.

This allows good heat dissipation, which reduces the chip temperature. Due to the good cooling, the LED can be operated with a higher current, which allows a high efficiency to be achieved.

For this reason, they are often used in large numbers in a single light source. For example, in lamps with a large beam angle, several LEDs are usually arranged in a circle. By combining different LED types it is also possible to achieve certain color spectra.

The abbreviation COB stands for chip on board. Here, the LED chip is attached directly to the printed circuit board with thermal adhesive. Due to the direct contact between the semiconductor and the board, the power dissipation can be dissipated even better than with the SMD version.

This further improves cooling, which further increases efficiency. Many futuristic lamp designs have only become possible through COB technology. On the other hand, a high chip density allows a high light output to be generated in the smallest of spaces.

This makes it possible to produce very bright LED spotlights, among other things. The functionality of an LED lamp has become much more complex compared to conventional light sources.