Cómo funciona un LED ⚡ Qué es un LED (Diodo emisor de luz)

one of the most common ways to generatelight is currently using an LED or light emitting diode and like the rest of the diodes as we saw in a previous chapter One of its characteristics is that it only allows the passage of electric current in one direction but we don't talk about why they emit light so in this chapterwe will see how an LED works but first I want to thank PCBWay for sponsoring this video PCBWay has a wide range ofPCB development solutions and right now you have an offer for the assembly of components from only 30 USD and including for freethe stencil used for the welding process so if you have any project in mind don't forget to visit their website LED lights have several features that make them one of the preferred options to illuminate such as having low energy consumption greater impact resistance and longer life and therefore they are available in many different formats but instead of going directly to analyze an LED we will start reviewing how a common diode works because in theory these can also emit light only that they do it inefficiently if we have a circuitwith a lamp and a power source energy will pass freely This is because electrons can move freely between metal atoms and when connected to the power source they are forced to move by adding a diode to the circuit depending on its position, thecurrent can pass freely or be stopped and the reason why it happensthis is because of its interior composition of the diode there is a semiconductor materialsuch as silicon more specifically, two types of this material if we took a piece of pure silicon and saw its atomic structure we will find that each atom has four valence electrons which are shared with others four silicon atoms around him forming a crystalline structure with covalent bonds that is, they share their electrons and therefore they have a total of 8 valence electrons per atom resembling noble gases the most stable elements known to man if you don't like chemistry don't panic the important thing here is that they understand that 8 electrons per atom is the numbermagical that keeps everything tightly connected in fact, so strongly connected that when a new electron wants to go through silicon the electrons that make it up cannot move hindering the flow of current but this can be changed through a process known as DOPING in which impurities are added to silicon to control its conductivity and convert it into a semiconductor of type N or type P if we add impurities that have 5 valence electrons instead of 4 then we will have atoms with a total of 9 electrons and since 8 was oursmagic number we could say that one of the electrons will be left over or be freer than others which will allow when we connect it to a power source it can move and act as a conductor This alloy is known as Type N semiconductor because it has surplus electrons, thewhich we remember, have a negative charge on the other hand if we do the Doping with impurities that have three valence electrons we will have atoms with a total of seven electrons that is to say that we would have a gap allowing electrons to be move through it and generating a movement of the gaps in the opposite direction since this alloy would have one less electron that the stable way this would have a positive charge and it would be called semiconductor type P Moreover, to simplify the visualization we will say that each hole corresponds to a positive charge in this way, when a PN junction is generated depending on the polarization of the voltage source, there will be two possible results if the positive pole is connected to the semiconductor type N and the negative pole is connected to the semiconductor type P the holes and free electrons will move away preventing an electric current from being generated This case is known as reverse polarization.

on the other hand, if we reverse the polarity of the voltage source semiconductor free electrons type N they will be able to jump through the semiconductor type py close thecircuit allowing the passage of the current This case is known asdirect polarization and it is precisely here that the physical phenomenon that produces the emission of light occurs if we return to our visualization of the atomic structure and we focus exactly on the point in which the two semiconductors make contact we are going to find that electrons are being moved from an atom with more valence electrons to an atom with fewer valence electrons this is extremely important because this difference in the amount of valence electrons It is also related to the amount of energy that they possess in other words, an electron thatfound in an atom with 5 valence electrons it has more energy than another electron in an atom with 3 valence electrons this means that every timean electron crosses this junction there is energy that is being lost but, as the law of conservation of energy says it is not created or destroyed, just transforms and in this case the energy that the electrons lost when jumping from one outlet to another became light or more specifically photons the fact that this happens at the atomic level has another implication since electrons move always from an atom A to an atom B the amount of energy transformed in each jump will be constant which in practical terms means that the emitted light will always have the same wavelength spectrum and also that by changing atoms A and B that is, the impurities withinsemiconductors we can emit lights with different spectra or referring specifically to the visible spectrum we can emit different lightscolors At this point we already know how the light is emitted but we still don't talk about why if this phenomenon occurs in a common semiconductor diode we don't see them shine continuously there are two reasons mainly the first one is that in many cases our eyes are unable to see the spectrum that is being broadcast I could not find an exact demonstration of this but if I found a video in which a solar panel emits infrared light when applying a voltage and a diode generates a voltage atbe enlightened all of which is related to the same phenomenon the second reason why a common diode does not shine it's simply the shape if we think the light is being generated only at the points where the two semiconductors are in contact how are we going to see them if for the most part this area is being covered in this patent in which the embodiment is described of one of the first light emitting diodes the solution is extremely simple move the semiconductors away from the connectors so that they do not cover the emitted light and reduce the thickness of one of them to such an extreme that light is able to pass through in a way we could say that this hasn't changed much to this day let's analyze an LED from the inside out the first thing we will need is a substrate in which to put the rest of the materials To this we add a layer of semiconductor type N and then another thinner semiconductor type P the order being important because when reaching the latter is when the transformation of energy occurs then we add some cables so that the electric current can flowbetween the semiconductors and the light is emitted being these extremely thin not to cover it technically only with this we already have a functional LED but to be more efficient we will add a small reflector to direct the light which will be integrated in one of the electrodes and before covering everything in a transparent epoxy resin so that the set is more resistant we will add one last element a layer of phosphorus although this is used only in some cases such as white light in this particular case the diode actually is emitting a blue light which upon impact on the phosphorus layer causes this to emit a more yellow light and it is the mixture of these two spectra the one that generates the perception of seeing a white light the last thing I want to talk about is RGB diodes that can produce multiple colors although the truth is not much mystery the RGB name refers to the colors that compose it red, green and blue Well, effectively within this type of LEDs there are three pairs of semiconductors specifically selected to produce each color and by independently varying thevoltage that passes through each of them the perception ofdifferent colors I remind you that I have several more animations on my channel in case you want to see them and also that you can support me in Patreon to make more videos That is all for now and see you in the next chapter.

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