Hello folks.
So in this video, I want to introduce this this very densely populated chart to you.
And what this chart is plotting, it's plotting the best
efficiencies, the best efficiencies obtained in the different research cells.
And this plot is available on the NREL website, which
is a National Renewable Energy Laboratory and they have done this,
you know, a very nice documentation of how efficiencies have evolved
across different solar cell technologies as a function of time.
So this chart is plotting these efficiencies
as a function of time.
And one of the reasons why, you know, why there's even a need
to make these charts besides to, you know besides to make a record of
these record efficiency cells,
one of the other reasons why NREL does
this characterization is that you know, there could be
there could be a research group or there could be a company
there could be a research group say research group
A or there could be a company say company B.
This research group could claim, you know, that they have made
a cell which has a 45% efficiency, it beats the Shockley-Queisser limit.
Similarlity company B can make another claim that our cell is 2% more efficient
than the best reported silicon cell. So, who is going to monitor it?
Who's go, you know who's going to verify these claims.
So, to kind of, one reason for making these plots is, or one reason
why NREL does this device characterization is to verify these claims made by
either individual labs or companies, and you know, they
verify or certify what their efficiencies in these cells are.
And whenever NREL finds a efficiency which which is
you know, much higher or which is greater than what
has been previously reported for that technology, that cell obtains
a, basically that cell obtains a point on this chart.
So each point on this chart, it represents
represents a record cell at that time. And
sometimes, you know, there are there are new categories which emerge also.
For example, you look at these orange curves over here, and they represent these
new emerging kind of PV technologies, such as dye-sensitized or organic
solar cells.
And you see that, you know, these have really started to appear only after 2001.
So there are new categories which, which,
you know, might appear, appear on these, charts.
And that, that represents that the new technology has been,
new technology has been, reported for solar energy conversion.
Similarly, you know, you see that sometimes
people might come up with a new method
of growing cells, or you know, some new manufacturing method.
For example, most of the most of the
crystalline cells have been either single crystalline or multi-crystalline.
But there has been a new, you know, a new process which is making these thin films
of semiconductor materials, which are still crystalline, and this
has been reported both for silicon, which has been
reported by the start-up company Solexel.
Similarly, this has been reported for
gallium arsenide by another company over here,
which is Alta Devices.
So many times you know on this chart you'll see new categories emerging
and that either represents a new technology for a, for a photovoltaic
conversion or a new process flow and that warrants a
separate, a separate color or a separate symbol on this chart.
So, you know, let's, let's look at what
are some of the record efficiencies, and the way
I, I want to do it is start from
the highest, and then go to the lowest efficiencies.
And so we'll just look at, you know,
if you look at the highest efficiencies over here.
So if you look at the highest efficiency, that is around 44%, and that record
is let me use the same color as that category so let me use a pink for this.
So if I look at the maximum efficiency,
it's around 44% and that record is hold by
this start up company Solar Junction.
And what you see over here that you know you can figure
out a lot about a lot about these multi-junction cells
just by reading or just by looking at this chart carefully.
So if you look at this chart for a multi-junction solar cell which
is plotted in this you know, in this pink kind of color over here.
So you notice that these are always, if you look at this caption over here.
so these are for usually involving
more than one junction.
So this is made up of three junctions, which is what currently holds the record.
There have been some cells which have been
reported for four junctions, but most of these points
over here, these triangle points over here,
they belong to these three junction-based solar cells.
Another thing I notice is that for
these multi-junction solar cells, the people report
efficiencies for non-concentrator, that is at a
concentration of one sun, and that is, you
know, then you achieve efficiencies which are
you know, in this range, the 37% range.
But at the same time when you apply
a concentrator or you increase the concentration of
the sun, by using, by concentrating the
sunlight, Then you get a much higher efficiency.
And the higher you go in concentration,
the higher the efficiency you get.
And this is, kind of, again, represented over here, where you
can see that this particular cell had a concentration of 406x.
And you had a concentration of 406 suns.
And the maximum efficiency, the record efficiency holding sun
currently, cell currently, it had a concentration of 942x or
942 sun.
And you can go higher than that, but of course that would heat up your cell.
So, so far you know, maximum concentration
which holds this record efficiency is around 940x.
So, similarly, you know, you can also see that when, which technology
is still currently being researched and which technologies have matured out.
So if you see these, some of technologies, for example,
multi-junction cells or if you see over here, if
you see these, organic cells over here, you
see that the efficiency are still rising when I'm,
when I'm, currently, you know, when, when I'm looking at
the years which are close to, the current time stamp.
So you see that the efficiencies are still rising as a function of time.
Versus is if you look at this square blue
chart over here, and this square blue chart over here,
this represents the efficiency of a single-crystalline cell.
We see that the efficiencies,
they evolved, you know they evolved a bit in the 1980's and 1985.
And you see this record cell of Sun Power over here.
But more recently, in the last decade these efficiencies have not moved much.
So pretty much, you know, people have squeezed out most of the
juice that they can out of these single crystalline-based silicon solar cells.
And, at the same time, so we started from the top over here, so we started with
this, multijunction solar cell, so that record-holding cell currently is
three junction, and if you use a highly concentrated light, and below that, if,
you know, if you look at efficiencies below that, they are again hold by,
these are held by these gallium arsenide-based cell.
which are mostly made up of single crystalline and
more recently there has been this work on making
these thin layers of single crystalline gallium arsenide, and
that is uh reported in these cells by Alta Devices.
Then if we, if we, if we climb down further in efficiencies, then we
find our good old friend, crystalline silicon-based solar cell,
which are the dominant, dominant PV technologies.
They hold, in fact, more than 85 percent of the market.
And you see they have efficiencies of maxing out at around 25 percent.
And then if we go further down this chart in efficiency, then we will see
these bunch of curves which are denoted by
this green color and they represent these
different thin film technologies and these thin film
technologies have what you know what has been
typically called a second generation of, second generation
of photovoltaics and there are many of these technologies.
So, there's a CIS which is Copper Indium Gallium Selenium.
There's a CdTe which is sold by
First Solar and there is amorphous silicon based technology.
And then there are these polycrystalline and nanocrystalline
based silicon technologies. And you see that, you
know, they have efficiencies which max out around 20 percent,
for CIS or CIGS based technologies. But they have
a much lower cost as a, you know, a much
lower cost of making this, making this PV module as compared
to some of these crystalline silicone based cells, so, you know,
they might still fare better on that dollar per watt metric.
But you see they're bunched up over here, so
they have efficiency of between 30 to 20 percent.
And you see these these
these green dots, which are filled with yellow,
and these represent these CdTe-based technologies, so you see,
these cells by First Solar, and they
have reported a maximum efficiency of close to 20%.
And then finally we reach towards the bottom,
so we reach this bottom of the pyramid over here.
But there is plenty of room over here and there's you see
plenty of action going on over here. See a large number of data
points in the, in the recent years and these belong to these what
is called as "Emerging PV." So what's included in here is these dye-
the dye-sensitized based cells or these organic solar cells.
You see they have, they have an efficiency which max out currently around 20%.
So, they have an efficiency of between seven to 12%, which seems to be very low,
but at the same time they can potentially be made using very low cost technologies.
The pipe dream for these kind of technology
is that essentially they can be made just
like we print paper, so we can have
a press which prints these emerging PV based technologies.
And so they, they lie at this
at this at this triangle, which is
at the bottom of this efficiency curve.
So this this efficiency curve, you know is something that I'll
I'll come back to when we talk about these individual technologies,
but it's a very good way to summarize or get your,
wrap your head around where these
efficiencies of these different technologies lie.
And what has been, how the progress
has been over, over the last three decades, okay.