The thing I want to talk about next, which is common to both your
which is common to any LCD, or any display, or any OLED, is the back plane.
So.
You know and we'll talk about other displays as well.
They'll have different things that you place on top so an LCD would have area of
liquid crystal OLED would have a area of light ommiting diodes.
But they will all have below them a back
plane which is consisted of transistors which drive these.
Either the liquid crystal or your organic LED's, and
running horse, or the stable technology in the
industry has been more facilicant, because you can deposit it very easily on glass.
>> But, it comes with a maximum mobility
of one.
And, you know, we talk about mobility when we talked about a transistor.
Then, you know, your
, but it's equally important and something you know, as big as this play.
And, this mobility of one only gives the frequency maximum frequency of 240 hood.
Also this amorphous silicone does not, these.
So remember I told you liquid crystal they don't need any color.
They just need a voltage.
So this amorphous silicone is okay for applying voltage.
But these OLED displays, these are organic light-emitting diodes.
So it's a diode and you need to drive it with current.
And if you need to drive OLED with current,
you need a high current and this amorphous silicone
transistor Just cannot comply, just cannot supply that amount
of current which is needed to drive or own it.
So there's a dire need to re, replace it with something else.
So this is how these backplane transistors look like.
They're made in a way that the gate is laid out first.
So first you lay out the gate, then you deposit your channels.
Your channels typically has been of amorphous silicon
But now people are, and then you deposit
your source and drain, and then etch, etch
them out and separate the source and drain.
But
this is wrong, this should be one. So, what people are trying to replace this
with is This material called IGZO, it's essentially a doped zinc oxide.
So either people are trying to replace it with metal oxides
or indium gallium zinc oxide, or some version of zinc oxide.
They have a mobility of 5 to 10, which is five times higher than 1.
they are trying to replace it with
instead of amorphous silicone replace it with polysilicon.
The four letter acronym for that is LTPS which stands for
[INAUDIBLE]
polysilicon.
It's low temperature because it's deposited
at, at a low temperature initially.
And that can give you a mobility of up to 50.
And so this IGZO, it's it's currently
being developed to replace Amorphous silicon for the LCD display.
The OLED displays, they essentially have a much
higher current requirement. They also have they
also need the current to be very stable at low current levels.
And these amorphous silicon or these amorphous zinc oxide transistors.
They always have variability in current when you operate at low current regime.
There are effects known as RTN or other variability effects.
So for
organic LEDs, the only option available is this lower temperature poly-silicon.
And that, this is, again, I talked about
.
I taught that LCD, all you need to do is apply a voltage and OLED you actually
need to drive this diode, so you need to supply it with with current.
And the way this low temperature poly silicon is made is that
You deposit amorphous silicon. And then you, you irradiate it with laser.
So it's made using a laser, sequential, laser process.
So you eradicate multiple sequences of laser.
And it converts into a polysilicon material.
And, this is what currently limits the side of your, size of your OLEG display.
Because they are not Big enough level available
that could crystallize a nine, nine meter squared space.
That's what currently limits the size of your display but this mobility is,
is needed for needed for your transistor. It depends
upon what resolution you want on your display
and what size you want of your display.
And then you have three technologies, amorphous
silicon, metal oxide, and low temperature polysilicon.
And all of these are eventually moving away from
amorphous silicon, either into metal oxide Or low temperature
polysilicon.
[COUGH]
So, you know, coming back to your question,
so we can now compare, now that we understand
these technologies a little bit, we know something how
a series works, which is used in your iPhone.
We know, now understand how the OLEDs work, which
are used in, you know, most of the Samsung phones.
We can now look at some benchmarking, and, you know, try to look at
now again, remember those terms that I threw around in the beginning.
So now, display technology, right?
We understand IPS LCD, right? What IPS LCD means.
We understand OLEDs.
Also we, we looked at that looked at that PenTile technology.
That's a way of putting twice the numer or claiming
you have twice the number of pixels especially the green pixel.
So that is what is used in your Galaxy The F3.
If you look at the picture resolution this is how they report 226ppi for
your iPhone. Your Samsung, it reports a resolution
of 306 pixels, again that's (no period) Six is only the resolution of your green.
Your red and blue have much lower resolution, because it uses that PenTile
technology.
So this is retina up to 10.5, this is retina At 11.2 only
for green, but if you're looking at blue and red, and if you're eyes
are good enough to distinguish blue and red, it's for blue and red, it's
retinal only when you place red 16 inch or higher away from you.
[COUGH]
Brightness, we talked about, right? So LCDs are much more brighter, so it
achieves the brightness of 500 or more. the
they are limited by their brightness by the efficiency of your
LEDs, so it has half the brightness of a Of your LCD display.
But the black level, look at the black level intensity.
So black level intensity in a LCD is minimum of .5
[UNKNOWN]
meters square. In in your S3
which uses a OLED. It's less than .005.
The black is really black in in OLED, and that
gives you an outstanding contrast of more than more than what
your human eye can distinguish. So that, that's Very big selling point
of OLEDs.
Colors also, they, they, so that black curve is your standard RGB gamma.
Your iPhone 4, if you look, it used to
have a smaller gamma as compared to the standard one.
This is again the trade off when you are examining the technology of brightness vs.
color season.
And how a brighter gamut as you know in technology.
You can do that by making stronger color phrases,
but at the same time it will reduce your brightness.
So iPhone 5 finally they have you know (no period) Exact RGB Color Gamut.
The alloy in the Galaxy S3 they always come with a color gamut of
more than what you need because you have these alloys they have very distinct
primaries so you always get a much larger
color gamut as compared to you know (no period)
your, your LCD band, whether it's a good thing or not.
I'm not sure.
Because sometimes people say it gives saturated
color, but some other people like it.
The gamma, which again, you can define by your output,
which is your input on this is on a log scale.
So your i-phone would have a way linear linear response with a slope of
exactly 2.2 or 2.6, you know, 2.6 is iPhone
4, this is more 2.3 which is close to 2.2. the
also have a similar 2.3 but it degrades that lower intensity because
it's LED, and it doesn't have exact linear response, it degrades
at lower lower
light level. Viewing angle, so we
talked about this, viewing angle is much better in OLED,
so if you have a LCD, if you look at thirty degree angle You only get 57% your
degraded by 57% or 64%. In in OLED, your only degraded by 28%.
So OLED, just by the inherited nature of it's technology, it has better viewing
Power, the power is actually very interesting thing.
We have a homework problem about it, but NCD power depends upon it depends upon
the efficiency of how efficiently you can get
out the light using data from your backlight.
and OLED depends upon the efficiency of your OLED.
Or if you're owners and then this is currently high but
it has been going down very steadily because
[UNKNOWN]
the LED themselves are getting better and
better with each technology innovation so it
would be way interesting you know, proposition
of a few years of, from now because
[UNKNOWN]
are getting better and better in terms of their efficiency.
Spectrum.
So, you know, it's election time, so it's, it's, we should have a poll and a quiz.
So
the thing if, if you have an image like, you know, on your smartphone which is
mostly black, and it has a slight You know
tinge of white text in middle. The question is, which, for
the same brightness, what will consume less power to generate this image.
Would it be OLED? Or would be
it LCD?
So how many people think that OLED
will consume less power for generating this image.
I don't know how many people think it's, LCD.
So, the thing is, most of this, most peculiar
thing about this image is that it's mostly black, right?
So, if it's mostly black, OLED doesn't have to do anything, right?
It just turns off And it's black, right? If I'm LCD I have to essentially
turn on all my killer, my color, fit, all my three pixels to generate,
you know, to, to, generate the black, right?
So it's a white black light and to generate
black I have to turn on all my pixels, right?
So.
For a image like this, a OLED display will have a, it just consumes 40% of the
power that your LCD consumes. So, what about this image?
So, if I took
this image and,
you know, generated the same image using either a OLED.
Are generated using the same MA as using LCD.
So how many think OLED would be more power efficient in reading that kind of
image?
[LAUGH]
So, for a, for a image like this, your
OLED consumes twice the power of your LCD, because
for your OLED, you know, that has to turn
on each of those pixels to generate the light.
So By the way, you know, if you look at most of the
default wallpaper that comes with your S3, they have a texture like this.
Most of your default wallpaper that come in your iPhone,
they have a texture which is more bright, because it
is suited that way.
So, I'm going to go 5 minutes over, but I
want to mention the emerging display technology which are out there.
So, there's a lot of stuff going on which is going to com out.
Some of it is already out, but.
And there's some x-factors, too, you know, which make it very appealing.
So most, most LEDs, most OLEDs and LCDs, they're not sunlight
readable because they, they work on the principle that you
generate light from the surface. So if you have if you have a light
background light that is strong which can easily diminish off the,
I talk about the LCD has a intensity of 500 candelabra meters squared, right?
Sunlight is ten times of that.
So if you just take it out in the sunlight, you cannot,
you know, neither of your Samsung or your iPhone would work in a sunlight.
So, you need to make it sunlight readable.
Flexible display is something, you know, which has been always talked about.
It never shows up to the party, but
[COUGH]
this is something which is out there, electrophoretic display.
So, this is what you use in your Kindle your old Kindle.
>> Alarm and it started to move away from it.
But, what how this works, it has again the,
the back plane is the same for all emerging displays.
The way it works is that you have these
dioxide and carbon dies and you apply a voltage.
And, depending on what voltage
you apply, you, you either get a black or a white surface It's it requires, it's
stable once you remove the voltage, so it requires no power, no power in standby.
[UNKNOWN]
makes it and it's it's very slow to switch, so
you can switch it you know, one page in 30 seconds.
So and also it's not available for a color.
The thing is, is something with son, it's shipping in some, with some selected OEMs.
And it combines this thing with the conventional SCT technology.
So half of your pixel is Is light
coming in but half of it is covered by this electrophoretic pixel.
So you can have, it work in your room
but when you go out, you use that electrophoretic display.
So this is again somehting these are
mostly currently way far out from commercialization.
This is a company that came form the University of Cininati and
the way tthat this works is that you have a liquid and it's it's response
to the electrical signal you apply Again, this is readable in sunlight.
This is the most coolest one, but the farthest away from commercialization.
You have one photonic And you change the
side effect depending upon where to you apply.
And this one system can
convey either red, green or blue.
So, and then you need to have an X-factor finally you
need to roll it out or it has to roll into something.
Something cool has to happen with it, right?
So these must, some of these enable us
to make us to make something display them with.
so
[MUSIC]