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What Is A LED And How Does It Actually Work ?

Posted on September 08 2016


Unless you have been living under a rock over the past decade, the term 'LED' should obviously ring a bell to you . Nowadays, most of the newer electrical appliances and lightings use this LED technology as its core, and not without it's reasons.



The most prominent reason for the recent popularity of the LED is it's significant energy efficiency over all other alternatives. However, it also possess other major advantages such as its wide selection of color temperatures, compact and small size, and its wide range of control as well as many other factors.

But what exactly is a LED and how does it works? Why is it the most preferred choice for electrical lighting and appliances today? We are going to dig a bit deeper today and let us begin with a brief introduction to the LED.



What is a LED?



Contrary to popular belief, the LED is not a recent invention. In fact, it's over half a century old, with its first recorded appearance in 1962.

LED stands for Light-Emitting Diode, a diode that emits light. In a LED's case, when the electric current passed the two terminals, it will emit light, hence the name and functionality. When it was first invented, it's still very expensive to make, highly inefficient, and can only emit a small output of light.

However, as illustrated by the Haitz's Law, the LED power output is doubles approximately every three years. Today, the LED has surpassed all other alternative lighting sources when it comes to price, efficiency, and power output.



The Anatomy of a LED



The LED has a physical appearance which can be seen in the photo above. The LED, as a form of semiconductor diode, is made with a semiconducting material mixed (or doped) with impurities so that the materials divide into a p-type, and n-type.




In between the p and n layer, there's a part called the active region, which is actually the boundary between the p-type and n-type materials called the p-n junction.

Both light and electricity are forms of energy, and as we understand, energy will not dissipate, but rather will always transform to another form of energy. When an electric energy passes through the P-N junction as mentioned above, it will be transformed into light. Hence it's called the active region of a LED.

The width of the active region, hence the difference of energy between the p-layer and n-layer, will determine the wavelength of the emitted light, which in turn, determine the color of light.



What Actually Happens in The Active Region



We have learned that the active region, or the p-n junction of a LED, is the part that emits light when an electrical current passes through, but what is the science behind it?


The picture above is a diagram showing the activities of electrons when an electrical current passes through. Called the forward bias, the free electrons (red dots) from the n-type material is moving to fill the holes (blank dots)  in the p-type material. We can see the light blue border which is the p-n junction or active region.

As the electrons move across the diode, they will release energy in the form of photons.  The gap of the p-n junction will determine the frequency of the released photon. Thus, when the gap is wide enough the photon frequency can be visible as light to the human eye.

Even when the band gap is short and the emitted light is invisible to the human eye, it can have its uses, such as the infrared LEDs in our remote controls. As mentioned in the section above, the size of the gap will also determine the color of the emitted light.



The Advantages Of The LED



Most of the advantages LED has over its alternatives are caused by the process discussed above. Electrons are invisible to the human eye, and their movement caused less disturbance compared to the gas movements found in fluorescent lamps, as we've discussed in our previous article.

Other notable advantages of the LED are:



Color Flexibility



As mentioned, to change the color of a LED, we need only to widen or shorten the band gap of the active area. This is a relatively easy process compared to those found in other alternatives where the whole material or chemical (gas) must be changed altogether. In some light source alternatives, changing the color can be simply impossible.






In general, semiconductor and transistor technology allows far more rapid advancement than the tube technology (incandescent, halogen, fluorescent.) This phenomenon allows LED nowadays to emit more lumens per watt than other light source alternatives.





LED can be smaller than 2mm2, and can be arranged together with other LEDs to form any shape. We may see a small LED flashlight, yet we can see LEDs arranged to form a huge UHD TV.






Semiconductors don't require the warm-up time typically found in older tube technology, and can withstand frequent on-off cycling. Compare it to the older fluorescent and incandescent lamps which can easily broke when cycled often, or older HID lamps that require a long time before it powers on.





LEDs can easily be dimmed by lowering the current, or using a pulse-width modulation. This feature is now widely used in smart control systems and the newer smart light bulbs.






LEDs generate very little heat over its usage and project very little infrared heat commonly responsible for damages to certain objects.






A LED has a significantly higher lifetime compared to other alternatives, and can reach 35,000 to 50,000 hours of lifetime. Fluorescent tubes, as a comparison, can only have 10,000 to 15,000 hours of lifetime in average, and incandescent lamps at only 1,000 to 2,000 hours.






Being a solid-state component, LED is more durable than fluorescent, incandescent, and halogen bulbs.




Is It Time to Switch to LED Lighting?



Still using the older fluorescent or incandescent bulbs? Although switching to a LED may be just a little more expensive up front, the longer lifetime and higher energy efficiency will justify your investment in the long run. Resulting in lower cost over a long period of time

Aesthetically, LED can also provide a more flexible design as well as color choices, which can be adjusted to any applications you may need.

As discussed, the LED technology is still rapidly developing at a tremendous pace, and will be more efficient with each passing year.

If you are thinking of switching, we would recommend you start off with a model that we use ourselves in our office. Price economically and UL listed, these bulbs (aff.)  would be a great starting point for you to begin your LED makeover.




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