Core ConceptsIn this article, you will learn about the chemical mechanisms underlying light-emitting diodes (LEDs). You will also learn about various types of LEDs, their advantages and disadvantages, and their extensive applications.What are light-emitting diodes?What does your morning routine look like? Perhaps you roll over toward your digital alarm clock, check the time spelled out in its bright numbers, and promptly tap the snooze button. Still half-asleep, you pick up your phone from the nightstand and begin sorting through your overnight notifications. Finally ready for the day after a shower and breakfast, you slide behind the wheel and power on your car. It’s a gray morning, so you need to turn on your headlights. As you stop at intersections along your commute, you patiently watch the traffic lights, waiting for them to switch from red to green.All of these devices – digital clocks, cell phones, modern car headlights, and traffic lights – use light-emitting diodes. Light-emitting diodes (LEDs) are a light source characterized by a junction diode with a semiconductor that releases photons in response to electrons passing through it. Other types of junction diodes exist, but an LED is unique in being a junction diode that produces light. A semiconductor conducts electricity more effectively than insulators (like glass and porcelain) but less effectively than conductors (like many metals).An illuminated white LED.Early precursors to what we now consider LEDs emitted light energy at various regions of the electromagnetic spectrum, but not the visible light region. Unfortunately, these were not very feasible for everyday use, since people could not readily detect this light. It wasn’t until the 1960s that electrical engineer Nick Holonyak created the first semiconductor that emitted visible light. This semiconductor, using the gallium phosphide arsenide (GaAsP) alloy, was the ancestor to the modern LED. But with a high financial cost and few practical applications, it still required more development.Over time, further innovation developed more cost- and energy-efficient forms, as well as more diverse colors, of LEDs. Nowadays, LEDs are ubiquitous across a wide range of industries and products, bringing our devices to life. To better understand how LEDs transform electric charge into light, let’s delve into the physical and chemical principles behind this.How do light-emitting diodes work?GaAsP was the first alloy that successfully emitted visible light in response to electric charge, but it’s not the only one that can serve as a semiconductor. Different alloys have different abilities to conduct electricity, and therefore different abilities to produce light. Let’s explore electroluminescence: the connections between chemistry, physics, and electricity that result in this light production.A Crash Course in LED AnatomyRecall that an LED is a semiconductor junction with a positively doped material and a negatively doped material that emits light when electrons pass through it. The flow of electrons (or any charged particle) is electric current, measured in amperes (amps). Stated simply, an LED is a semiconductor that lights up when current flows through it.Anodes and Cathodes and Current, Oh My!The LED is classified as a diode because its structure has two different materials that form a p-n junction. When current flows through the LED’s semiconductor, it flows from one terminal to the other. One terminal is electron-rich, so it carries an overall negative charge and can function as a cathode. By contrast, the other terminal is electron-poor, has a relatively more positive charge, and serves as an anode.Within a circuit diagram, the symbol for an LED is always drawn pointing from the anode to the cathode. Two arrows, indicating light emission, distinguish this LED symbol from an ordinary diode symbol.In a diode, we call the cathode the n side (“n” refers to its negative charge) and the anode the p side (“p” meaning it carries positive charge). Instead of having electrons like the n side does, the p side has electron holes. You can think of an electron hole as the absence of an electron. For this reason, electron holes have positive charge. An electron and an electron hole have the same magnitude of electric charge, but with opposite polarities, since the electron is negative whereas the electron hole is positive.Exerting a greater electric potential on the p side stimulates electrons to flow from n side to the p side. (Electron flow occurs only in this direction in a diode, although this isn’t the case for all electrochemical cell types.) When stimulated by the electric potential difference (voltage), excited electrons in the n side freely move toward the p side. To reach the p side, they must cross the depletion region, the insulating space between the n and p sides. The depletion region itself is almost completely devoid of electrical charge, except for a few ionized impurities. It essentially has no electrons and no electron holes, because the applied electric potential has driven these charged particles away.How Electron Holes Make It HappenHowever, an electron can’t move unless there is a space available for it to move into. This space is the electron hole. The p side has electron holes, so electrons can flow from the n side, across the depletion region, into the p side. As these electrons flow toward the p side and occupy the holes (spaces) there, the p side gradually has no more space available for electrons to move into. By comparison, the n side has more space than it started with. In another sense, as electrons flow from n to p sides, electron holes simultaneously flow from p to n sides.This is basically another example of diffusion, where a substance flows from an area of higher to lower concentration. In this case, electrons are initially more concentrated in the n than the p side; electron holes, more concentrated in the p than the n side. Diffusion helps make the electrons flow toward the p side and the electron holes flow toward the n side.Initially, the n side has negative charge because it contains electrons, while the p side has positively-charged electron holes.Applying a potential difference to the electrodes creates an electric field.The electric field draws electrons toward the p side and electron holes toward the n side.RecombinationAs the flowing electrons reach the p side and encounter electron holes there, and as the flowing electron holes encounter electrons on the n side, recombination occurs. In recombination, an electron “fills” (joins together with) an electron hole. Since the electron and the hole exist at different energies, recombination produces a photon with an energy equal to the difference of the electron and hole energies. Most often this is equal to the bandgap of the semiconductor. Most recombination happens at or near the depletion region, where both types of particles come into contact with each other.In this way, we can see that LEDs are an application of oxidation-reduction chemistry (redox reactions). Reduction, or gain of electrons, occurs at the cathode and oxidation, or loss of electrons, occurs at the anode. This redox reaction does not happen spontaneously in the LED. An electrical energy source, like an electric potential difference, must be introduced in order to give rise to the redox reaction.The sequence of a p side, a depletion region, and an n side, as observed in a semiconductor diode, is known as a p–n junction. Let’s investigate how these redox reactions produce light – and color!The layout of a p–n junction as seen in a semiconductor diode.ElectroluminescenceIn the process of electroluminescence, the semiconductor releases light energy through photons, as a result of current flow. But where does the light come from?Electron holes and excited electrons (or, in the case of an LED, injected electrons) are at different energy levels. In the moments immediately after an excited electron recombines with an electron hole, the electron has filled the hole and is no longer in an excited energy level. The excitation energy is freed as a photon, which we perceive as a transient burst of light. As recombination happens to many electrons inside the LED simultaneously, they emit a lot of photons, so the LED takes on a steady glow.Recombination is the basis of electroluminescence. Electroluminescence, the production of light due to electric current, is just one type of luminescence. Many other types of luminescence exist, including chemiluminescence (light production caused by a chemical reaction) and bioluminescence (light produced by an organism). In an LED, light production is only the beginning: what’s truly impressive is how we can engineer this light to our advantage.Creating Color in LEDsThe first LED, developed by Holonyak, was red. Over sixty years later, we now use LEDs of all colors, lending themselves well to new functionalities and applications in design and art. Having multiple colors on a single device allows that device to communicate several distinct messages. For instance, consider how the red, yellow, and green LEDs on a single stoplight each bear unique meanings.How do these LEDs, having identical structures and chemistry to each other, manifest in different colors? Keep in mind that our vision perceives the visible light region of the electromagnetic spectrum. Within this region, longer wavelengths of light appear red to us and shorter wavelengths appear violet, with the rest of the rainbow spanning the wavelengths in between.Also remember that LEDs emit light as photons, which carry light energy. This emitted light is of a specific wavelength depending on the alloy used in the LED’s semiconductor. The color of the LED corresponds to the wavelength of this particular photon’s light energy. That is to say, selecting a different alloy manipulates the color of an LED.A variety of monochromatic colored LEDs.Let’s take Holonyak’s original alloy, gallium phosphide arsenide (GaAsP), as an example. Using GaAsP in the semiconductor results in a red LED. But GaAsP is one of many alloy options; there are other alloys that also create red light, and still more alloys that produce other colors.As we know, distinct wavelengths distinguish different colors in the visible light region. Electrons that release higher-energy photons, translating to light energy with shorter wavelengths, produce colors like violet and blue. Contrarily, if the electrons emit lower-energy photons with longer wavelengths, this yields colors closer to orange and red. Middle-of-the-road wavelengths lead to yellow and green colors.The electromagnetic spectrum. Numbers represent wavelengths in units of meters.To alter the color of an LED’s light, you can alter the alloys within its semiconductor. This is referred to as doping the semiconductor, and the alloy used to alter the semiconductor is called the dopant. It’s possible to dope the n side, the p side, or both. When designing an LED, we select a specific alloy based on what color light we want the LED to emit.To do this, we have to consider how each element in the alloys will interact with each other. If the dopant will serve as an electron donor to the initial alloy’s elements, then this dopant will introduce additional valence electrons to the semiconductor. These extra electrons do not stay bound to the atoms, so they move about the semiconductor, contributing to its electric charge. By contrast, using a dopant that serves as an electron acceptor will break some existing bonds in the semiconductor, producing electron holes.This is the rationale behind doping. Whether a dopant serves as an electron donor or acceptor depends on which elements are in the initial alloy, and whether we are doping the n side or p side.So how does a white LED produce its color? White light is comprised of all colors of light, so it incorporates all wavelengths within the visible light range. In order to yield white light, we need an LED that can produce all colors. There are two ways to achieve this.RGB LEDsThe first method to produce white light using LEDs is through RGB LEDs. RGB stands for “red, green, blue,” three colors that can combine together to make new colors. For example, combining red and blue makes purple. An RGB LED contains red, green, and blue bulbs within the same LED unit. Each of the bulbs’ intensities can be adjusted individually. When all three bulbs are of the same intensity, contributing red, green, and blue in equal proportions, the resulting color is white. If you were to adjust the intensity of only one or two of these bulbs, it could produce other colors of the rainbow.Why use red, green, and blue as opposed to any other three-color combination? The human eye contains red, green, and blue cones, which are photoreceptor cells that respond to wavelengths in the visible light region. Using red, green, and blue as the color components of an LED provokes an equal magnitude of response from all three types of cones. When red, green, and blue cones all have the same magnitude of response, the human eye perceives the color as white.The additive color model conceptualizes RGB color combinations.Phosphor ConversionThe second strategy to obtain white light is to utilize a phosphor coating. A phosphor is a substance that emits light in response to electromagnetic radiation exposure. By taking an LED that emits a single color, and coating the LED in a phosphor layer, it’s possible to convert that color into white. Let’s explore this in a bit more detail.Making a phosphor-converted LED (pcLED) is as simple as covering the original monochromatic LED in a phosphor layer. The phosphor material itself is approximately yellow in color. But what happens within this layer to filter the original color into a white color? The phenomenon that’s responsible for this is the Stokes shift. We say that the Stokes shift has occurred when a photon is emitted at a lower energy (longer wavelength) than it was absorbed at.The Stokes shift explains differences in wavelength (and, by extension, differences in energy level) that arise during emission.The Stokes shift is useful for describing how light converts to white from any other color. Most commonly, a pcLED begins with a blue LED whose light undergoes the Stokes shift when the LED is coated with a yellow phosphor. The phosphor absorbs the blue light from the LED, but emits yellow wavelengths of light. Since yellow wavelengths are longer (lower energy) than blue wavelengths, the Stokes shift has occurred, and the result is emission of white light.Take another look at the additive color model image showing how individual colors can combine to produce other colors. The center of the image, where the blue segment and the yellow segment overlap, is white. This is a visual way to understand a phosphor’s purpose, which is to create white light by combining blue and yellow light.Theoretically, we could use other combinations of LED colors and phosphor colors to produce white light. Any two segments of the additive color model that overlap in the white segment would suffice. However, the only feasible pcLED involves a blue LED alongside a yellow phosphor coating. This is because the Stokes shift works by decreasing a photon’s energy during emission, i.e. emitting the light at a longer wavelength. Blue has the shortest wavelength (with the exception of violet) out of all colors in the electromagnetic spectrum’s visible light region. This means that blue LEDs have energy that can undergo a Stokes shift, whereas other colors would undergo the Stokes shift less effectively.For example purposes, let’s say our initial LED was red rather than blue. This red LED emits photons at relatively long wavelengths, so our eyes perceive them as red in color. The red light would then pass through a phosphor. Normally, the light would undergo the Stokes shift as it passed through the phosphor, and then the phosphor would emit it as yellow light. This scenario is impossible if the starting light is red. Red light is already lower-energy than yellow light, so red light cannot undergo a Stokes shift to create yellow light. Instead, the better option is to begin with a high-energy color (blue) and use the phosphor to convert it to a lower-energy color (yellow).Color is just one aspect of light production. To maximize the other aspects, such as brightness and resolution, electrical engineers needed to build upon the LED. This is how the organic LED was born.Organic Light-Emitting DiodesAt this point, we’ve already discussed how various chemical elements can affect LEDs’ light production. For the most part, these have been limited to metallic elements, in the form of alloys. But by introducing organic elements into the LED’s circuitry, the impact is game-changing.Organic molecules facilitate light production in an organic light-emitting diode (OLED), a variation of the traditional LED. More specifically, hydrocarbon chains within the OLED react with electricity input to yield light. The structure of an OLED is more complex than a traditional LED’s, but their fundamental physicochemical principles and processes, including recombination, are similar. Let’s take a closer look.Building upon the technology of traditional LEDs, OLEDs are the mechanism behind captivating digital displays.How are OLEDs structured?Recall that traditional LEDs consist of a p–n junction between a semiconductor’s two layers (one p-type and one n-type layer). When a potential difference is applied to a traditional LED, electric current passes through the semiconductor. Meanwhile, electrons flow in the opposite direction and recombine with electron holes at or near the depletion region. This is the basic framework of an OLED too, but we also need to accommodate the organic chemistry principles that set OLEDs apart from traditional LEDs.We can think of an OLED as a six-layered sandwich. The substrate is the sandwich’s bottom base, made of glass. Working upward, we have an anode layer, which has a positive charge just like in a traditional LED. On the other side of the anode layer is the organic layer, which is itself made of two films called the conductive layer and the emissive layer. The organic layer is where the magic of organic chemistry happens. These films each consist of different organic molecules (hydrocarbon chains). The conductive layer’s molecules transmit electron holes from the anode layer while the emissive layer carries electrons from the next layer, the cathode layer. The cathode layer has an overall negative charge due to having these electrons. Finally, topping off the sandwich is the seal, made of glass like the substrate. Both the seal and the substrate exist to protect the OLED’s architecture.Essentially, the organic layer in an OLED is analogous to the depletion region of a traditional LED. It’s where electrons and electron holes encounter each other and recombination can occur. And, true to its name, the emissive layer is where the electrical energy produces light. Let’s see how.A visual diagram of the individual layers of the OLED “sandwich.”How do OLEDs work?As with a traditional LED, it all begins with applying a potential difference across the two electrodes. This launches an electric current, and with it, an electric field. The anode and cathode conduct electric charge through the organic layer that separates them. Due to its overall positive charge, the anode attracts electrons to itself; in other words, it provides electron holes to its neighboring layer, the conductive layer. Likewise, because the negatively-charged cathode provides electrons to its adjacent emissive layer.Returning to our sandwich structure, we see how these electrons and electron holes are drawn, in opposite directions, to the midpoint of the organic layer. Now that it has fewer electrons than before, the conductive layer’s charge is more positive relative to the emissive layer, which received the cathode’s electrons. Considering this charge difference, the conductive layer is comparable to a traditional LED’s p side and the emissive layer is comparable to the n side.At this stage, the electron holes in the conductive layer need to be filled with electrons. Electron holes flow more readily than electrons do, so they transfer from the conductive layer to the emissive layer. During this process, the electrons fill the electron holes, creating excitons. As in a traditional LED, this recombination causes a fleeting release of light energy, or photons. This light emission is visible through the glass seal and substrate, so we perceive the OLED as illuminating.I’ll Have One Electricity Sandwich, PleaseTo recap, this electroluminescent step happens in the emissive layer, one of the carbon-based films in the middle of the OLED sandwich. Current passes through these hydrocarbon molecules, but the photon production and release continues only while a current is being applied. Applying more current results in a more intense brightness.In part due to this intensity, OLEDs are renowned for their superior display quality when used in screens. Through this sandwich format, it’s possible to control each pixel individually. To make a pixel appear black, all you have to do is switch off the OLED behind it. There is no backlighting whatsoever, so the resulting black images have a deeper darkness than they would without the use of OLEDs. It also enhances contrast between light and dark pixels for a more refined display.How do OLEDs produce other colors? Doping with different alloys is not necessary to change an OLED’s color because OLEDs don’t employ the traditional LED’s p–n junction structure. Instead, all it takes is inserting a colored filter above the substrate or beneath the seal. By placing the filter between the glass layer and one of the electrodes, the light passes through the filter during emission. In doing so, the light adopts the color of the filter.The filter, as well as the emitted light that passes through it, is either a red, green, or blue color. We can combine each resulting red, green, or blue OLED in different amounts to produce new colors according to the additive color model. To create white color, OLEDs in each of the three RGB colors would be incorporated in equal quantities. To create black color, as mentioned above, the OLED would simply be turned off.When it comes to OLED-powered screens, there is an alternative method for producing color. Screens are made of pixels, an array of display units that work together to produce a cohesive image. Subpixels, each one taking on a red, green, or blue color, exist as even smaller units within a single pixel. A screen that uses OLEDs arranges these subpixels in a pattern that make the overall image sharper, or higher-resolution.OLEDs vs. Traditional Light-Emitting DiodesOLEDs and traditional LEDs have comparable energy efficiencies. So why utilize OLEDs at all, when traditional LEDs are already available? Most people would agree that OLEDs have a stronger aesthetic appeal. Their ability to produce a more diffuse light, which translates to a less harsh glare, makes OLEDs a great option for home lighting. For other devices, OLEDs provide both form and function.For instance, it’s possible to manufacture OLEDs in a thinner format than traditional LEDs allow, resulting in more lightweight devices and giving OLEDs a central role in design-centric applications. Picture the newest devices on the market: a sleek smartphone, a practically weightless computer monitor, a paper-thin television. These elegant features are possible because of OLEDs. Behind the scenes, OLEDs are brighter and capable of a shorter response time (and thus a faster refresh rate) compared to traditional LEDs. As a result, screen displays are of higher quality and transition between images more seamlessly.Unfortunately, there are drawbacks to using OLEDs as well. Due to having higher manufacturing costs, devices with OLEDs boast bigger price tags than those with traditional LEDs. The life expectancy of an OLED is also shorter than a traditional LED’s. And as the organic substances in an OLED break down over time, the device’s display can experience new problems with its intensity or color. With more innovation, the OLED manufacturing process may be able to resolve some of these flaws and make OLEDs an unbeatable choice for electric applications.Why do we use light-emitting diodes?The development of LEDs was a groundbreaking advancement in electrical engineering, even extending beyond to other fields, such as the tech industry. That being said, LEDs are not the only mechanism we can use to produce light from an electric circuit. What are the reasons why LEDs should, or should not, be used in certain applications?Alternatives to Light-Emitting DiodesTo understand the role that LEDs play in the electrical world, first we need to evaluate other common alternative lighting options.Incandescent LightingWhen someone says “light bulb,” you probably picture an incandescent light bulb. Incandescent lighting is a very basic form of electricity. Incandescent light bulbs contain terminals and a filament within a glass exterior. Current flows through the terminals in order to heat the filament. The metal filament conducts heat. After sufficient heating, the filament glows brightly, producing light.There are a few subtypes of incandescent lighting. Halogen lighting is one example. A halogen light bulb contains a halogen in gas form, and its filament is made of tungsten. Current flows through the filament, causing some tungsten to evaporate. The evaporated tungsten reacts with the halogen gas in the halogen cycle reaction, which redeposits some evaporated tungsten particles back onto the filament. This way, every time the bulb is lit, the tungsten particles can repeatedly evaporate and return to the filament. This cycle contributes to halogen light bulbs having a longer lifespan than incandescent light bulbs.An incandescent light bulb.A halogen lamp utilizing a halogen light bulb.Compact Fluorescent LightingPerhaps the most distinctive-looking light bulb is the compact fluorescent light (CFL) bulb. In its most common form, this type of “bulb” is actually a simple tube that spirals upward from the base. A fluorescent material coats the interior of the tube, which contains a ballast along with argon and mercury gas.The ballast supplies an electric current, which moves through the tube, exciting gas molecules along the way. Upon excitation, these molecules produce ultraviolet light. When this ultraviolet light comes into contact with the tube’s fluorescent interior coating, the coating absorbs the light energy and emits it in the form of visible light.A compact fluorescent light bulb.Advantages of Light-Emitting DiodesOver decades, electrical engineers have refined each of these lighting options, but it’s hard to beat the benefits of using LEDs. There are several properties that make LEDs a dynamic competitor in the electric field (ha!).Energy EfficiencyWhat may be the LED’s strongest selling point is that it’s a highly efficient light source. A light bulb is more efficient when it requires less energy input to yield a certain energy output. We can consider this energy output in terms of light energy or heat energy, but light bulbs produce both. In an LED, the majority of electrical input is devoted to achieving its main purpose – producing light. The same can’t be said for other light sources.Take incandescent light bulbs as an example. Heat (and lots of it – several thousand degrees) must warm up the filament before any light emission can happen. By the time the bulb manages to produce light, it has already been releasing lots of heat. This is why incandescent bulbs tend to feel hot to the touch. Due to losing most of the energy input in the form of heat rather than contributing to light production, incandescent lighting is a relatively inefficient light source.Luminous EfficacyThis is where LEDs take center stage as a strong alternative to incandescent lighting. An LED and an incandescent bulb could produce the same amount of light, but the LED would have required less energy input to get there. Moreover, a larger proportion of that energy input is contributing to light production in an LED than in an incandescent bulb. Another name for this proportion is luminous efficacy. As a consequence of having higher luminous efficacy, LEDs also create less heat output than other forms of lighting. Less heat production makes them fit for use in electronic devices that could be sensitive to overheating, such as cell phones.Eco-FriendlinessSo how do LEDs compare when stacked up against CFLs? Early marketing focused heavily on the fact that CFL bulbs are more environmentally-friendly than their precursor, the incandescent bulb. The more efficient a light bulb is, the more eco-friendly it is, because less energy is necessary to light it. LEDs surpass both CFLs and incandescent bulbs in this regard. In addition, CFLs contain small amounts of mercury gas that get released when the bulb eventually breaks or is disposed of. (It’s worth noting that routine use of a CFL bulb doesn’t present any mercury exposure.) But, boasting a mechanism that doesn’t involve mercury, LEDs create less pollution and pose less risk to the user’s health.And don’t let their small size fool you – LEDs are surprisingly powerful. Due to their high energy-efficiency, their lifespan typically surpasses that of an incandescent, halogen, or CFL bulb. As far as size is concerned, an LED’s small format makes it a versatile choice for devices that are tiny or have an intricate lighting design. In fact, having a more compact shape than other lighting options gives LEDs better optical control, directing light where it ought to go, instead of dispersing it in all directions like other bulbs do.Disadvantages of Light-Emitting DiodesLumen DepreciationDespite their compelling qualities, LEDs aren’t infallible as a light source. Remember that LEDs produce light in response to an electric current passing through them. Therefore, an LED’s brightness is directly proportional to how much current passes through it; more current means brighter light.It may seem desirable for an LED to emit as much light as possible, but an LED can burn out if too much current flows through it. Unlike other light sources, like incandescent bulbs, LEDs don’t burn out suddenly when exposed to too much current. Instead, an LED’s brightness weakens over time. This weakening is referred to as lumen depreciation.When an LED experiences too much lumen depreciation, it emits light ineffectively and will eventually need to be replaced. However, we can minimize lumen depreciation by taking the simple precaution of using a resistor. A resistor is an electrical component that resists current flow within a circuit. By placing one or more resistors prior to an LED in a circuit, in series with that LED, less current will reach the LED. Therefore, the LED will emit less light than it’s fully capable of, but its lifetime will last longer. Using a resistor with a greater resistance value will decrease the LED’s brightness.A diagram showing an LED’s role in a simple electrical circuit. Note that the LED symbol points in the direction of current flow (I). Resistors (R) can be used within the circuit to manage the LED’s intensity.Battery LifeThe other problem with using an LED at its maximum brightness level is that doing so tends to drain a battery faster. The LED requires more electrical energy in order to emit brighter light, so the LED’s battery (or other power source) will deplete more quickly than if the LED were used at a moderate brightness. This is especially important to consider when including LEDs in a device, such as a cell phone, that relies heavily on battery power.What if you want the functionality of an LED but admire the aesthetic of an old-fashioned light bulb? Luckily, nowadays there are LEDs available that are designed to resemble incandescent bulbs. In spite of its shortcomings, one of the LED’s biggest strengths is its adaptability – allowing you to have the best of both worlds.Applications of Light-Emitting DiodesGood or bad, LEDs are everywhere, and their uses continue to grow. Their adaptability is the very feature that makes them so widely relevant. With a multitude of different colors, formats, and intensity levels, there’s an LED suitable for just about any contemporary device.They’re not just for complex gadgets like robots, either. LEDs provide backlighting to your smartphone, your television, and maybe your computer keyboard too. They’re everywhere from your supermarket ceiling to the adjustable overhead lamps commonly used in dental chairs and operating rooms. (Something to think about during your next root canal.)Or, you might encounter LEDs while you’re on the road. Notice them in the car headlights passing you by (and in the navigation lights on the airplanes flying overhead). Whether present in an eye-catching billboard, street signs, or atop an emergency vehicle, LEDs help get important messages out quickly.And be on the lookout next time you’re seeing a show – LEDs power sports facilities, spotlights, and even art displays. Or perhaps your next celebration will feature an LED glow stick or decorative holiday lights. Simply adding transistors, resistors, and capacitors to the same electric circuit gives the LED a strobing or flashing effect. The only thing more endless than the applications of an LED are the possibilities.A computer keyboard using RGB LED backlighting to create a rainbow gradient effect.A string of multicolored LED holiday lights.A traffic light with red, yellow, and green LEDs.ConclusionLight-emitting diodes (LEDs) are such resourceful light sources that they have reinvented technological devices, hardware, and the field of electrical engineering. In response to an electric current, LEDs work by recombining electrons with electron holes within their semiconductor, which excites the electrons and results in the release of light energy after excitation ends. Doping the semiconductor with a different alloy, using RGB LEDs, and phosphor conversion are methods of implementing color variations. Organic LEDs (OLEDs) use a six-layered structure including hydrocarbon molecules to produce brighter, sharper images. Hailed for their energy efficiency and versatility, which make them effective alternatives to incandescent and compact fluorescent lighting, LEDs are widely integrated into our daily lives due to their extensive applications.
