Trystan Casey
Light-emitting diodes (LEDs) are semiconductor devices that emit light when an electric current flows through them. This phenomenon, known as electroluminescence, was first observed in 1906 by Henry Joseph Round, who noticed that certain crystals emitted light when a voltage was applied. Since then, various materials have been discovered to exhibit electroluminescence, including semiconductors, phosphors, and even diamonds. The specific colour of light emitted depends on the energy band gap of the semiconductor used, with different materials producing light in the infrared, visible, or ultraviolet range. LEDs have become widely used due to their low power consumption, thinness, and ability to produce bright, energy-efficient white lighting.
| Characteristics | Values |
|---|---|
| Name of phenomenon | Electroluminescence (EL) |
| Process | Radiative recombination of electrons and electron holes in a semiconductor produces light (be it infrared, visible or UV) |
| Materials exhibiting EL | Silicon carbide crystals, semiconductors containing Group III and Group V elements (e.g. gallium arsenide, gallium nitride, indium phosphide), certain organic semiconductors, zinc sulfide doped with copper or silver, diamond with trace amounts of boron |
| Light colour | Dependent on the energy band gap of the semiconductor used; can be controlled by manufacturers |
| Power consumption | Low compared to neon or fluorescent lamps |
| Thickness of material | Thin |
| Directionality of light | Lambertian radiator; brightness is the same from all angles of view |
| Light homogeneity | Perfectly homogeneous |
Explore related products
What You'll Learn
Light-emitting diodes (LEDs)
In LEDs, electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The wavelength of light, and therefore the colour, depends on the type of semiconductor material used to make the diode. The band gap of the semiconductor determines the energy required for electrons to cross it, which in turn determines the colour of the emitted light. The intensity of the light depends on the amount of power being pushed through the diode.
White light can be obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device. Alternatively, white light can be produced by using individual LEDs that emit the three primary colours—red, green, and blue—and then mixing all the colours to form white light. Another method is to use a phosphor material to convert monochromatic light from a blue or ultraviolet LED to broad-spectrum white light.
LEDs only light up when voltage is applied in the forward direction of the diode, and no light is emitted if voltage is applied in the reverse direction. The efficiency of LEDs decreases as the electric current increases, and higher currents also produce more heat, compromising LED lifetime.
Electric Guitar String Tension: Higher or Lower?
You may want to see also
Explore related products
Electrons and photons
The behaviour of electrons and photons in electrically energized materials is governed by the photoelectric effect. This effect describes the interaction between light and electrons, where photons of light carry energy that can be absorbed by electrons within the material. When a photon possesses energy greater than the binding energy of an electron, it can cause the ejection of that electron from the material. The kinetic energy of the ejected electron remains unchanged, while the rate of electron ejection increases with the intensity of the incident light.
The photoelectric effect has been extensively studied, with Albert Einstein making significant contributions in 1905. Einstein proposed that light energy is composed of discrete packets called photons, each containing energy proportional to the frequency of the light. This hypothesis explained the experimental observations of the photoelectric effect and played a pivotal role in the development of quantum mechanics.
Photons themselves can be generated in various ways. One method is through the change in energy states of electrons. When electrons transition from a high-energy state to a lower-energy state, they can emit photons. This process is observed in blackbody radiation, where the heat of an object is felt from a distance due to the emission of photons. Additionally, electrons with high kinetic energy, such as those in particle accelerators, can produce high-energy photons when their path is altered by a strong magnetic field.
The understanding of electrons and photons has led to numerous practical applications. For example, LEDs have become a common light source in various devices, offering bright and energy-efficient lighting. Additionally, the photoelectric effect is utilized in switches that respond to light, such as nightlights and photomultipliers. By harnessing the behaviour of electrons and photons, scientists and engineers have developed innovative technologies that continue to shape our daily lives.
Connecting an Electric Keyboard to Your Mac: A Step-by-Step Guide
You may want to see also
Explore related products
Electroluminescence
The most common electroluminescent devices are composed of either powder or thin films. Powdered zinc sulfide doped with copper or silver produces light in the greenish or bright blue range, respectively. Thin-film zinc sulfide doped with manganese emits orange-red light. Another example is gallium arsenide (GaAs), a semiconductor commonly used in light-emitting diodes (LEDs). LEDs are semiconductor devices that emit light when an electric current flows through them. The earliest LEDs emitted low-intensity infrared light and were used in remote-control circuits.
Electroluminescent technologies have relatively low power consumption compared to other lighting technologies, making them valuable in the advertising industry for billboards and signs. EL manufacturers can precisely control which areas of an electroluminescent sheet illuminate, allowing advertisers to create dynamic content that is still compatible with traditional advertising spaces. EL films have the unique property of appearing equally bright from all angles, making them well-perceived by the human eye.
Volta's Electric Pile: Unlocking Electricity's Power
You may want to see also
Explore related products
Incandescent lightbulbs
An incandescent lightbulb, also known as an incandescent lamp or incandescent light globe, produces light by heating a filament inside the bulb until it glows. This process is known as Joule heating. The filament is typically made of a material with a high resistance, such as carbon or tungsten, and it is enclosed in a glass bulb that is either evacuated or filled with inert gas to protect the filament from degradation.
In 1906, William D. Coolidge developed a method for creating ductile tungsten filaments, which were then used in incandescent lightbulbs sold by General Electric starting in 1911. Since then, incandescent lightbulbs have become widely used for various applications, including regular lighting, specialty lighting, and heat lamps.
The Electoral College: When Does It Vote?
You may want to see also
Explore related products
Fluorescent bulbs
The central element of a fluorescent bulb is a sealed glass tube. The tube contains a small amount of mercury, an inert gas (usually argon), and a phosphor powder coating on the inside of the glass. The tube has two electrodes, one at each end, wired to an electrical circuit. When the lamp is turned on, the current flows through the electrical circuit to the electrodes, and the voltage causes electrons to migrate through the gas from one end of the tube to the other. This energy changes the mercury from a liquid to a vapour.
As electrons and charged atoms move through the tube, they collide with the gaseous mercury atoms. Most of the photons released from these mercury atoms have wavelengths in the ultraviolet (UV) region of the spectrum. This UV energy is then converted to visible light by the fluorescence of the inner phosphor coating. The phosphor coating is heated by the difference in energy between the absorbed UV photon and the emitted visible light photon.
Fluorescent lamps come in various shapes and sizes. They are more energy-efficient than incandescent lamps, but less efficient than LED lamps. They also have a higher initial cost than incandescent lamps, but this is offset by their lower running costs. Fluorescent lighting is declining in popularity, being replaced by LED lighting, which is more energy-efficient and does not contain mercury.
Resetting an Electric Safe Lock: A Step-by-Step Guide
You may want to see also
