Noob Question Time - What produces the light on the LED?

[soulrider]

Ok, I know this is probably LED 101 here and I HAVE searched and read some articles on LEDS and how they are put together, etc. However, I am still fuzzy when it comes to understanding by what method the LED actually generates the light. I understand in an incan light there is a filament which heats up and starts to glow thus producing light. In a HID there is kind of a spark gap where light is generated (if I've got that right). However, it is my understanding with an LED there is no filament. Also, are there different types of LEDs? And what I mean by that is this, there are the typical cheap bulb-like LED's with two legs/wires sticking out that you see used in electronics to light up things. Is there another kind that is more like just a computer chip. The reason I ask that is after unscrewing the bezel and lens from my Olight M20 the LED appears to be more flat and 'chip-like'. However, now that I look more closely I can see what appears to be a faint reflection from what seems like bubble or dome over the LED. So, is the LED used in the flashlight the same (in function) as the LED's I'm used to seeing or is it a whole new animal? Thanks to anyone who wants to try to educate me on this or point me in the right direction on what to research. Thanks.

Oh and this whole flashaholic thing...I thought I was not going to be prone to that since I just wanted a nice bright high tech LED light since I've never had one before..that's all..no desire to collect them no desire to have multiple lights..(just my Olight M20) However, I find myself really really liking some of the different Ti lights I've seen that people have made (small Ti light with the piston system...drool..). I also seem to be gravitating toward this Tritium concept...maybe I'll stop at two lights...I can do that...right? It's not to late.

 

[Chodes]

What have you read? Have you checked Wikipedia - the LED page seems to answer your question.

 

[Marduke]

Basicially the package can differ greatly, but the basic physics remains the same in your examples.

Most white LED's today work the same way.

In short, a chip produces blue light, which is partially converted into other wavelengths using a phosphor layer on top of the chip.

That wiki article has the details.

 

[Badbeams3]

Put another way...we don`t really understand it...so we just point you in the right direction...maybe you can make sense of it. Myself...I think there`s a mini magic genie rubbing his lantern so fast it sort of glows.

 

[soulrider]

Thanks for the replies. Thanks for answering that the packaging can vary but the concept is the same. Makes sense. I didn't get anything out of the Wiki article. I guess I just don't get the 'electrons recombined with holes thing'. I've read that before in different articles. I was just looking for maybe a different way to explain it but maybe there isn't one and it's just above me. I've never gone to Wikipedia (until now) as I've never ever really considered it a valid source for information based on it's format. But then again you've got to evaluate just about anything your read on the internet and take a good deal of it with a grain of salt. I like the genie idea by the way.

 

[Biker Bear]

LEDs are diode crystals - that is, they only easily conduct electricity in one direction. This is because the parts of the crystal have additives that bias the electrical nature of that portion - one part has an additive that makes it deficient in electrons ("type p" for positive), or have an excess of electrons ("type n" for negative). The spots in the Type P crystal where there "should be" an electron are called "holes" because you can think of them as gaps in a regular structure.

As current flows through the crystal, electrons are drawn off from the p-type crystal - and as new ones move in, cross the p/n junction and "snap" into the "holes", that causes a release of energy in the form of light.

This is admittedly a bit oversimplified, but I hope it gets the idea across.

 

[StarHalo]

Some refinement of Biker Bear's explanation -

A diode is a component that allows current to flow in only one direction - it does this by combining on one side some material that has more positive charge (P-type, too few electrons makes it positive) with some material that has more negative charge (N-type, too many electrons makes it negative) on the other side.

So now we've got a diode with its two sides connected, nothing is separating them physically - with no charge being applied to our diode, the negative and positive sides mingle and combine freely, so right in the middle of the diode there's a balanced area, where all the atoms are no longer positive or negative; this is called the depletion zone, because it creates a large neutral buffer between the two sides - with no charge, our self-balancing diode just separates itself and does nothing.

Once we apply a charge in the correct direction, everything starts moving (if we apply a charge in the wrong direction, it just reinforces the negative and positive of each side and the depletion zone becomes even larger - no charge flows). The positive and negative sides begin flowing into one another with much more energy, so the depletion zone shrinks and vanishes. All the extra electrons on the negative side begin filling the "holes" (places in atoms where electrons are supposed to be but are missing) on the positive side.

Here's where the magic happens - when a free electron fills a "hole", it does this by shifting some of the other electrons in the atom down a step from where they are - picture a line of people in chairs and one chair is open somewhere in the middle; someone new comes by and wants to sit down on the end, so each person on the side of the new guy scoots down one chair allowing the new person to sit down on the end. This is precisely what happens in the atom, the new electron makes some of the other electrons already in the atom scoot down so it can take its place. When an electron scoots down, it releases a photon, and a photon is an individual "particle" of light.

So in summary - the two-sided but normally-neutral-in-the-middle diode gets a charge put across it, and this moves the electrons on one side into the holes on the opposite side; when each electron arrives, the already-in-place electrons scoot down to accommodate it, and this releases energy in the form of a photon.

Do this with trillions of trillions of atoms all bundled together in one space, all the photons being emitted in huge numbers, and presto, you've got a light source, a diode that emits light, a Light Emitting Diode.

 

[Zeruel]

....and yes, it's too late. You won't stop at two lights now. Welcome to the club. :devil:

 

[soulrider]

Biker Bear & StarHalo: Thank you for the great explanations!! That makes more sense now and is understandable. I assumed from reading about the P and N sides and electrons moving from one side to the other that it was similar on a much smaller level to some type of gap being bridged and that was when the light was emitted but never really got a good grasp of it until now, thanks!! Thank you for taking the time out to write out that description instead of just saying 'go read about it' since what I'd read so far wasn't sinking in for me. I appreciate it.

Zeruel: I was afraid someone was going to say I couldn't stop at one or two lights. I really want a nice small titanium light...I'm going to stop after that...ok, I"m going to try. I've seen some pics of some people's collections of titanium lights and it just blows me away. The cost involved alone is staggering.