TechStuff Classic: TechStuff Stares at OLEDs

love all things tech. And now I'm going to talk to you a little bit about classic episode, an episode of tech Stuff that we published way back on March two thousand and twelve called tech Stuff Stairs at O LEDs, O L E d S. Chris Palette and I sat down to talk about what are O LEDs, how do they work, and why are they important? And I think it's funny to listen to this older episode because when we were recording it back in two thousand twelve, oh LED screens were still very much in that R and

D kind of prototype stage. You didn't really see them in very many consumer products. And these days where you're seeing them and all sorts of stuff from smartphone too, tablets, to laptop computers to television sets. So it's neat to

see how things have changed. Enjoy this classic episode. I think by when I first started at How Stuff Works, oh lads, we're still very very much in the prototype stage, and you didn't really see anything on the market at that time, the consumer market anyway, they had an O LEDs type screen and now they're much later in the prototype stage. But we're kidding the lads. Actually, now we're getting to the point where we're finally seeing them scaled up to large screen TVs. But for a long time,

the biggest screen you're gonna get with something like eleven Yeah. Yeah, Well, the genesis of my joke being that people who are really interested in OLED technology have been waiting for them to come out for a very long time, and it seems like they're they've been in development of some kind for a for a long long time. They've been actually pretty common in smaller screens like smartphones, rins for example. Um,

they're they're really great for that. They use less energy than a lot of the other technologies and they're excellent for that. But that's you know, getting them scaled up has taken a long time, and the people who have been waiting, I'm gonna buy an old TV like, well, you know, I wouldn't hold my breath. Well, but finally

they're starting to hit now. But and and also the other thing people have been waiting for, and it's one of the types we'll talk about in a little a little further in in the podcast is the flexible oh lady, that idea of having a display that is actually malleable, that you can bend it around things. And you know, you might use that to have a foldable display. That's what a lot of people talk about. But there are other things you could use it for, Like you could

use it in displays. Stay in a store where you've got round columns and you could have a display wrapping around this round column. Uh yeah, things like that. Well, yeah, and it's uh, and that's the thing about it. I think, Um, despite the fact that it's taken a while to get law er oh lad screens, the technology will be worth the way. But I think it's uh. I think it is a good idea to go ahead and talk about the similarities. And there I think three major similarities between

the technologies red, green, and blue light. Well, the purpose of all all the technologies we're talking about here, you know, plasma l C D and uh you know the oh lads or l E D screens and organic l E D screens. Um, you know, it's it's to display information and it shows us light. Um. The trick is really

how they go about doing that. And we've talked about some of the other technologies in the past, like for example, plasma uses uh gases ionized gas, and basically you they show the different colors by running a charge through the gas and then look like l c D uses liquid crystals, and these liquid crystals actually form a barrier between light and the clear part of the screen, and then the l c D these through various running an electric current

through change shape and that allows light to pass through and there's some color filters in there and that's where we get the displays through that. So that's a liquid crystal display. L E d s are light emitting diodes and we've had those around for for quite some time and they're pretty efficient. They're more efficient than a lot of other forms of lighting. But an O l e D, as Chris had mentioned, is an organic light emitting diode.

And you might think, well, what how that huh, And it really comes down to uh kind of a an organic sandwich. Yes, And the thing is, uh, they're not terribly different from from the typical l E d s, but it's it really comes down to the materials used to make that sandwich. So they're they're they're very thin, alright, So an O L D it's it's solid state, all right, And it is usually between one to five hundred natomie eaters thick, which is pretty thin. That's according to UH

to most estimates. And this does change from one source to another, but it's about two hundred times thinner than a human hair in diameter. Now, human hair is actually come into a variety of diameters. It's like one person's hair might be thinner than another's. Some people have clear hair like me, My hair is invisible to the human eye. But yeah, at any rate, the two hundred it's an average, So it's two hundred times smaller than the diameter of

human hair. And uh, it's they're different layers within this sandwich, right, and that's what is creating the light that you see. And there's the basics the the bread on this sandwich, if you will, is our pair of electrodes. Right, you've got your cathode and you've got your technically, you also have the substrate. This substrate is the foundation that the O LED sits upon. So substrate is also part of this. But I'm looking mostly at the components that actually make

the lad work. Right, So, yeah, you've got the cathode and the anode, and you've got the jobs of the cathode and the anode are to create a circuit for electricity to flow through, right, right, The electrons flow from one to the other. Yea, from the cathode to the anode. And in a way you have to kind of think of this in uh interesting terms, like, so, cathode is

injecting negative particles into this o led sandwich. Are you positive? Yes, I am positive that they are negative electrons, is what cathodes are putting into their The anode is creating, well what we call them electron holes. They're positive. It's they turn an element to a positively charged element. They actually pull electrons out of it, and so now it's positively charged. So that means that the electrons coming from the cathode are attracted towards the anno side. Hey, you're pretty cute.

And so it has to pass through the other layers of the sandwich. And there are two or three other layers, depending on the type of oh ledge you're looking at, but really the two layer is the most common, So I'll just stick with that. So you've got your emissive layer, this is the layer that actually emits light, and you have your conductive layer, which is the layer that attracts the electrons through the other materials. So if we're looking at top to bottom and the bottom is the substrate,

then the top layer is your cathode. Next down you have your emissive layer, that's where the light comes through. Then you have your conductive layer that's what's pulling the electrons down. Then you have the annode layer. That's what's really pulling the electrons down. It's what's allowing the conductive layer to pull these electrons through. And then you have the substrate. So, uh, why are we getting light? Boy?

This this gets into some interesting physics here. Okay, So you've got the electrons coming through from one side, you've got the electron holes coming through from the other side. So in a way, you can think of negative charge and positive charge. I know that sounds weird, but just go with me here. And when those two meet, the molecule that they meet at becomes uh, actually drops an electron into that positive hole, and as a result, there

is a difference in energy. It releases some energy as a result of that that reaction, and that energy is released in the form of a photon. And we've talked about this before about how if you excite an atom, you know, by telling you it's going to dine world or something, and the electrons moved to a higher energy state.

When those electrons move back down, once that energy has has been removed from the system, once the electrons move back down, they have to release that extra energy, and they often will do this in the form of photons, which we perceive as light. That's exactly what's going on here. Actually, I saw a great video on this uh M my t S site where a professor was explaining how oh LED's work by shocking the heck out of a pickle.

He had a had a cathode and an anode um attached to a pickle and was running a very high electric current through it, which was making the pickle glow. And it was this is what was happening. You had the positive charge in the negative charge meeting and the molecules where it met at that's where it was releasing this electron and uh and and releasing a photon or or it was the electron states were moving down and the photons were being released, and that's why we were

getting light. Um pretty cool. Actually, I kind of wanted to build one, except for the fact that I'm sure I would probably electric you myself. For a second there, I thought you were girk in my chain. Ha ha. Anyway, so when we're talking about electricity, we're not talking about a lot. It said, these are pretty efficient, so we're talking in a realm of just a few volts that are needed in order to excite these molecules so that

they emit light. That's one of the major benefits of old screens is that they don't require as much electricity as some others. You know. Of course, plasma TVs are are notorious for using a lot of electricity. Well, you have to keep pouring in electricity to keep that gas ionized. So yeah, plasma display is not They've gotten a lot better last few years, but is it is, by its very nature, is not the most environmentally friendly way of

creating television. Not that TV is terribly environmentally friendly no matter how you do it, but but it's it's less So yeah, plasma has a reputation for being for being less energy friendly. So yeah, there there there have been some better ones, but still uh and those two different layers of molecules are are are organic, but they're organic plastic thick. It's pretty cool organic plastic like poly aniline

and polyfluorine. Okay, all right, you know Pollyanna, you know when you when you say we're organic plastic, that sort of sounds like it's oxymoronic, like you know organ chuah wa um. Well that that's actually UM. We should talk about to the different types of OH leads because there are r G B OH lead screens and then there's the white lead screen UM, which sort of uses a color sandwich to UM, and by by activating red, green,

and blue, you get white UM. And uh. You know those the red, green and blue are are pressed together in the same pixel. So by doing that you can you can have the have basically a pure white UM and it's it. It works a little slightly differently than than the others simply because of at UM. There are people say that it has a longer life than the traditional O lead screens UM, but that is supposed to be one of the advantages of it UM. And it's also possible to uh to scale the white OH lead

screens up a little easier from what I understand. Yeah, it's also been talked about as a potential replacement for things like fluorescent lights, where not just for displays, but for actual lighting, because that's it's even more efficient than fluorescent lighting is. And uh, you know you don't have

that mercury that you gotta worry about in fluorescent lights. Yeah. Guys, if you have those little fluorescent bulbs, which are you know, more energy efficient incandescent bulbs will good on you, but be very careful with them, yes, because those suckers do contain some very toxic chemicals in them that can be

very dangerous. Yes, you do not want to bust them, right, So the O lead lights might be a nice alternative to that, you know, if if it's efficient enough so that they make economic sense to the consumer, because you know, you gotta worry about that, uh, and also the fact that they don't have these toxic chemicals necessarily inside them.

If they are just as efficient or more so, then makes perfect sense to go and switch to a We're gonna get back to our discussion about how oh LEDs work and what they are all about in just a second, but first let's take a quick break to thank our sponsor. There are actually several different types of oh LAD screens just LAD displays. We talked about the foldable oh LEDs. Now, these are using a substrate that is flexible. So you know,

your typical substrate. When I think of substrate, I think of something that is that is, you know, pretty solid, or sometimes it can be a little brittle or whatever, but it doesn't bend. It's not bendi bendy. Right. Well. The the idea being that you're going to build your

circuit material on top of this material. So I mean you're this it's a board, so you you know, you're I'm going to add the stuff to it, right, Yeah, Usually you want something that's fairly solid, although you know, obviously for other applications you would need something that's flexible. Let's say that you want to create a display on say a jacket, which might very well be something not

necessarily that the consumer would ever see. But let's say an advertising company creates this, uh, this type of of jacket that can have a flexible screen on the back of it, and then next thing you know, you've got this new way for at trade shows where people can show off cool technology and it's literally playing on their backs. Um, I mean, I could even imagine it going so far as to let's say you've got a courier service and you are sponsored, they run ads on your back as

you you're a bike courier. I look forward to seeing that. I look forward to seeing all the accidents that will happen as result people turning their heads to see what to watch. Yeah, they're like, I want to follow this guy another mile. I have to see how this turns out. Clearly that if you did that, you would have to make very visually stunning types of ads that don't need any audio. That would be that would be the real challenge there. Look, I'm just trying. I'm just I'm just

trying to create some jobs out there. That's what I'm trying to do. Okay, But you also have you have your passive matrix oh LED. Now passive matrix, oh lads. You know we talked about the cathodes and the anodes. Well, that's not necessarily a sheet on top of you know, when I said sandwich, it sounds like you're talking about solid sheet. That's not necessarily the case, although that can

be done a passive matrix oh LED. What it does is it arranges the cathodes and anodes into strips, and one sets strips are vertical and the other sets strips are horizontal. So you could think of it like all the anodes are streets and all the cathodes are avenues. So at these intersections where the cathode and and O meat that's where you have your pixels and your pixels

of course, that's the point of light. So when you talk about how many pixels the display has, as so many points of light it is capable of displaying at one time more than that, it would be a very low resolution television. Uh. The so this is one way of doing that where you have the just at the intersections of these strips, that's where the pixels are uh.

Not terribly efficient compared to other oh leads and uh and also for all of these screens, if you're wondering about controlling brightness, that's a function of how much electricity is flowing through the system. If you're pouring more juice into it, it's gonna be brighter less juice not as bright, which makes sense. Next, we have the active matrix OH lead and this has a full sheet of the cathode and and it's sort of like the sandwich example I was giving earlier. So in this case, there is a

film transistor that is uh gotta. It's an anode layer overlay, and that's what forms the matrix. Uh not the kind that NEO goes through with all the zeros and ones, but this in the it forms the same feature as the intersections on the passive matrix. OH lead, tank, I eat an exit. Oh gosh, wow, out of all of those, you know, I'm surprised you didn't say I know kung fu or just whoa uh you got your transparent oh lads. Now these are really super cool. Like everything every single

element in this oh lead is transparent. So when light is uh is flowing through this system, then you see it projected within a clear screen, and when it's not, you can just look through the screen. Now, this is used in things like heads up displays, so you know you're flying exactly flying a plane, driving a car or whatever. If you've got a heads up display that can show within the uh the windscreen or or cockpit screen or whatever,

that is very likely a transparent oh lad. I've also seen this used in smart Windows, which was something new. I mean, I had heard about smart windows before, but it was the first time I had seen one was at CS where I think it was Samsung that had it. Where it's a smart window. What that could display information and it could do things that give you like little

information like news items or the weather or whatever. Although when you're looking out a window, if you need a weather report, when you're looking out a window, you're not being terribly observant. Well, it might be nice to know what the temperature is going to be. You can open the window. Oh okay, all right, so you're looking at the future forecast. Alright, fine, fine, yeah, you know, all right, Okay, I withdraw my objection. Uh what about active matrix leeds.

I talked about those. That's one of the that's the one with the thin film transistor. Do you want to just okay? Now they used as a lot in the phones. So oh yes, yes, yes, yes, that's the one that does have that thin film transistor I was talking about. That's the one that ends up taking the place of

the intersections. The thin film transistor itself has the connections on it on the anode side where it activates where the pixels are, and these pixels are active the fact that they are so thin is a benefit when you're talking about these electronic devices. It makes it so much easier to uh, you know, fit it into these things

tablet form factors and smartphones. Yeah, if we were still using if we were using things like l c D technology for all of these devices, they would be significantly or at least noticeably larger, like thicker and and somewhat heavier. And I mean heavy being a relative thing. But in the case of it, every ounce counts. Yeah, and in a tablet or something like that, you know, if it adds six ounces. Yeah. There's one more type of O lead thy talk about, which is the top emitting OH lead.

And this has got a substrate that is either opaque or reflective, and they are often used. This is often uh like this, this is just one subtype of O lead. It can actually be combined with another type of O lead. So, in other words, that active matrix old we were just talking about, that method of display could be combined with the top admitting OH lead. Uh. And this is something that's often used in things like smart cards. Future Jonathan here saying, hey, these old leads are pretty great. I

bet pasted Jonathan and Chris would have really dug them. Anyway, it's typ for us to take another quick break to take our sponsor. So lots of different applications of oh leads, not just uh displays on phones or um or TVs or or even you know, computer monitors that kind of thing. Uh. It's interest seeing because even though it sounds pretty complex, really it's simpler than things like l c D technology.

It is. It is much simpler in the grand scheme of things, um, even though it's more advanced technology, and it's taken years to kind of get the prototype, the manufacturing process efficient enough so that we can build screens that are at the size that we're used to. Even so, you know, we have mentioned that, yes, there are television screens coming out like large ones TVs that use oh LAD displays. They are incredibly thin, like to the point where you can't even really get a good picture of

them when you look at them in profile. UM. However, they also tend to cost a princely some Yes, that's what I was getting at, is that we have reached the point where the manufacturing process has allowed us to build these, but they're still prohibitively expensive. For I'd say the majority of the consumer market, new TV is likely to cost you several thousand dollars. We're talking like ten grand easy, ten tho dollars for lad screen easy. Um that that's a lot of money for a new television set.

I would not be prepared to spend that much on a TV. And if you're talking about using a competing technology that costs say one fifth of that, you know or or or yeah or less? Well, yeah, it depends I think the last thing. So for example, I I purchased an l E ED l c D h D t V for um way less than that, like less than a tenth of that. And so you look at that and you're you're saying, yeah, the the technology, the display technology is clearly superior in that clearly clearly huh,

in that it's got a very crisp picture. The colors are are very true true blacks. Yes, because you don't have that backlighting, just like plasma. Plasma does not have backlighting, but l c D does, which is why if you've ever had l C D television new mine is an l c D t D. It's just back split by l E D S. Yeah, so that's why L E

D l C D. Yeah, so when you both. But but if you're watching in a dark room and it's a scene that is like someone walks into a pitch black room in the house, or there's suddenly like a blindfolds being put on or whatever, you start to notice like, wait a minute, my my screen is actually kind of glowing, like it's not really black. It's just really dark, and I can see that there's light trying to shine through. Hey, it's pitch gray in there. Yeah, that's not a true black.

But oh lads, and uh and true l E D t v s and um uh plasma TVs they have true blacks where because there's no light coming through right that that part of the screen is inactive, So it's as dark as it's gonna get. Um. Yeah, so that's another nice thing that the color ratios on these contrast ratios are really really good. The but yeah, it's even though it's superior, it's just it's gonna take a while before that price is gonna drop low enough for it

to be within the reach of the average consumer, I think. Yeah. And the flexible displays are are always off too. I think those will probably we'll price see those used in commercial projects first. Oh sure, well, I mean that's where the money is. People are gonna be willing to spend that for their company to do advertising or to do whatever. Um, I'm sure some mogul will add them to their UM sports stadium just because they can. Yeah. Now, eventually, look

at what I got. Yeah, eventually we may see that

incorporate into consumer goods. Like I could imagine a like an o lad bracelet, right, like a thick oh lad bracelet that fits arounder wrist and it can display the time, and it can do other suff sure where it would be really thin, so you can have one that is you know, is you can even get some of different lengths, so you can get one that fits your wrist really snugly, and then you can show all this uh this UM content off, Yes snugly, and the battery and and processor

and everything would be on the underside of it, so it's not always on display. Uh that unless you're you know, a nurse, in which cases the other way around. Uh the but yeah, that I could easily see that happening further down the line. Um, And the potential for oh LEDs is pretty high. I mean we're like I said, We've already seen it in consumer goods like like smartphones and tablets, where it's really helped make these things as

sleek and slender as they possibly can be. I can't wait to see by the time this podcast goes out, will know more about it. But I can't wait to see how the new iPad looks, UM. And I'm sure that it's going to be using an organic light emitting diode screen, possibly a retin a display. We don't know because as we're recording this it's the week before Apple has its big announcement. Maybe it won't be an iPad

it all. Yeah, that's true, and I could come out that the March seventh, uh discussion it has nothing to do with an iPad, in which case I'll just be like, well, I guess we're waiting around, but I would be surprised to see that because the iPad two came out in large last year. Yeah, whenever south By Southwest rolls around, that's when it's time for a new iPad. Al right, guys, Well, I think that wraps up our discussion on oh LEDs UM.

They're pretty cool and yeah, if you want to learn more about them, please go to how Stuff works dot com and look at how oh LED's work. We have a lot of of information on it. There are a lot of different illustrations that show this process of the electrons moving from the cathode to the an out and exactly how that creates the the light that these layers are emitting. Um, it's very interesting stuff and it makes

it a lot easier to understand. And we have come to the conclusion, my friends, of yet another classic episode of tech Stuff. I hope you enjoyed it. I know I did. And if you have any suggestions for future episodes of tech Stuff or questions or comments, send them my way. The email addresses tech Stuff at how stuff works dot com, or you can drop me a line on various social media. If you want to learn how to contact me there, head on over to our website

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