How do LEDs work ?

In order to understand LED, or to call them by their proper name, Light Emitting Diodes, we need to understand semiconductors and electroluminescence. Semiconductors are elements (or compounds) which have conductivity between that of conductors (like metals) and insulators (like glass). A process called doping is used to add impurities to the semiconductor so as to create two different types of semiconductor layers in the same chip. This happens because the impurity modifies the electron configuration of some of the atoms of the material, thereby rendering some atoms electron deficient (possessing “electron holes”) and some electron surplus. One layer becomes electron deficient, while the other becomes electron surplus. The junction of these two layers is called a p-n junction, and this p-n junction forms the foundation of all LEDs.

How do LEDs work

Electricity being essentially the movement of electrons through the element, it can only flow from the negatively charged electron-excess region to the positively charged electron-deficit region, or in other words, electricity can flow only in one direction across the p-n junction. Now electrons move from the negatively charged atoms to positively charged atoms, they fill the deficit areas (called “electron holes”) in the positively charged atoms. While filling them, they emit photons by the process of electroluminescence. These photons are “particles” of light, and when they are emitted in sufficient quantity, we can say that the p-n junction is emitting light.

The process by which this is turned into a fully functional Full spectrum LED grow lights is too complex to cover here, though if you want a more in-depth analysis, you can refer to this paper.

Evolution of LED Performance



Commercial marketing of LEDs had begun much before of course, with Texas Instruments getting the first patent for the commercial LED in 1962. The product them came up with, however, cost $130 apiece, which made it extremely costly for the time. Over the years, however, prices of LEDs have dropped, and today we have LEDs being used in the great majority of electrical implements.
History of best LED grow lights

Such diversification of LED applications influenced the grow lights industry rather late. It was only in the early 21st Century that attempts were made to create arrays of 120 5mm diodes to produce commercial grow lights. Such arrays made use of up to 5 different types of LEDs, two in the red light region, one in the orange/yellow region and two in the blue region. Such an arrangement attempted to create the natural absorption spectrum of chlorophyll and carotenoids, which are the primary energy conversion materials in the plant leaves. The original attempt offered very poor wattage, leading to less than promising results when applied in indoor gardening. Coupled with the fact that one array cost about $100, this method offered too low a rate of returns on investment to be sustainable in the long run.



Today LED grow lights offer a wide range of spectrums and users can choose to buy light arrays catering to various “bands” of spectrum depending on what the needs of their plants are (see “Types of LED lights”). More importantly, the prices offered today allow the average grower to recoup the price difference in just 18 months (assuming the replacement of 1000W of HID lighting with 350W LED lighting, which provide the same light output due to greater efficacy of the latter). Indeed, the time period is even lower in cases of large commercial entities. It is not surprising, therefore, that LED lights are rapidly displacing MH and HPS grow lights as the favorite type of lighting for indoor horticultural twilight projects.