The goal of the course is to give students awareness of the largest alternative form of energy and how organic / polymer solar cells can harvest this energy. The course provides an insight into the theory behind organic solar cells and describes the three main research areas within the field i.e. materials, stability and processing. NOTE: This course is a specialized course on organic solar cells. If you are looking for a more general solar cell course, we strongly recommend Introduction to solar cells (https://www.coursera.org/learn/solar-cells).
Testing and Encapsulation
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來自 Technical University of Denmark (DTU) 的課程
Organic Solar Cells - Theory and Practice
657 個評分
從本節課中
Solar Cell Fabrication
By the end of this module you will be able to: -Describe the lab scale techniques and the pros and cons -Describe the difference between coating and printing -Identify the different coating and printing techniques.
與講師見面
Eva BundgaardPhD, Senior Scientist
DTU Energy
Frederik C. KrebsPhD, Professor
DTU Energy
Mikkel JørgensenPhD, Senior Scientist
DTU Energy
Morten Vesterager MadsenResearcher
DTU Energy
Now, once we've completed the solar cells by either
one of few in-line printing or coding steps or completely by discrete processing steps,
we of course need to test them.
And there you also need roll-to-roll processing machine.
We have several machines for this purpose.
We have machines that can do IV testing,
so under illumination of light.
We have multiple LBIC systems,
where you basically make an electric image of the solar cell.
We also have roll-to-roll,
simply voltage or testing methods where we can apply contact to the device
in a roll-to-roll fashion and do some sort of measurements that
we think is of particular interest at the point that any possible time.
Now the testing is of course critical because we want to know
if we've made a new ink for a certain purpose,
we want to confirm that it actually works or that also that the solar cell works,
especially because we later on have to patch those solar cells.
So laminate them or encapsulate them,
and then patch testing of the individual solar cells at least becomes difficult.
I can already see now what should be apparent by now,
that if you process these cells as fast as you've seen in the videos,
you'll realize that it's impossible to go in and measure these by hand.
So it needs to be fully automated.
And generally when you do roll-to-roll development,
you have to think in a manner that everything scales to the same speed.
So it doesn't make sense for instance,
that you roll-to-roll process one or two of the layers.
And then you have to cut out the cell and measure with a voltmeter,
or perhaps cut it out and put it in evaporator.
Or do discrete non-roll-to-roll processing step
in a roll-to-roll process. This will never work.
Even at the very end,
when you've finished a solar cell,
ideally the end user or
your solar cell phone should also operate in a roll-to-roll setting.
Otherwise there'll be a bottleneck or you slow
down the further processing or integration of your solar cell.
Now the testing is, of course,
extremely important especially because you're going to continue work on the phone.
In a solar cell case,
we want to package it,
so typically we process the solar cell directly on a of moisture and oxygen barrier foil.
We have this barrier foil that is then impervious to water and oxygen,
but the solar cell is just printed on the backside of
this and that means it's exposed to the atmosphere.
So when you operate the solar cell by shining light at it,
it will break down very quickly as you learned
in the sessions on stability of the organic layers.
So it needs to be packaged.
And before we package it,
because the packaging is an expensive step, it's time consuming,
the risk or the potential loss
you can have from either packaging something that doesn't work,
or destroying something in the process of packaging,
is large because you have to remember that
all the processing steps that lead up to the final packaging step are then lost.
So it could be good cells that are lost because you did something wrong at the end.
So the problem with a serial process like
this discrete process is: that the longer you get into the process,
the more expensive the roll is,
therefore the more expensive or the more hard any loss will be to you.
Therefore testing is essential.
You can at least avoid
packaging areas or lengths of foil that doesn't work or that you shouldn't package,
and you can focus on the stuff that works really well.
Now so after testing of course, it's very easy,
I already showed you we have this barcode,
so we know each piece of foil.
And when you do roll-to-roll testing you also read the barcode.
So for for this final solar cell with this given serial number,
you know exactly how those different cells,
or how all the solar cells on this particular motif,
or this particular foot of foil material, how they perform.
This is also then read both when we do testing,
but then also when we laminate.
So the lamination or the packaging is a totally different process.
There will take a piece of clean barrier foil,
we apply an adhesive of some sort,
it can be different types, plastics, acrylics, etc.
We force two the foils together through a nib,
we get a thin adhesive layer there.
And there are different lamination methods that are possible.
There is the pressure sensitive adhesive.
It is the easiest one to carry out
on a laboratory scale or even on a small roll-to-roll scale,
because the glue is already prepared on a liner,
pretty much like double-sided sticky tape.
So you can apply the glue to one side of the foil,
and then you just laminate the two foils together with the glue already present,
and your solar cell is done.
The disadvantage of the pressure-sensitive adhesive approach is
that the permeability of water and oxygen is quite high.
So the the quality of the packaging in terms of permeation of water and oxygen is
not as good as what you can get with the two other methods that are currently available.
One of them is where you have a liquid ink that is then cured by either UV or just heat.
Or you could have something called hot-melt,
where the glue was already applied and it's in a dry form,
it can be very thin, and then you have to heat this up over a hot roller so it melts,
and then you force the two foils together
right at the nib with the hot rollers and then just after the rollers,
the foiled is cooled and then this molten glue solidifies,
and you have a perfect seal.
So the hot-melt and UV curing methods
are totally different from the perspective of temperature,
you need some temperature for the hot-melt methods,
where you don't forcibly need it for the for the UV curing glue.
If it's a liquid glue that you cure
by UV or heat-- or simply heat of course, then you need heat.
Now at the moment at this pilot scale level,
UV curing adhesives are by far the most performing,
whereas in the ultimately up-scaled version,
it's likely that the hot-melt type sealants
will outperform all other glues both in terms of cost and in terms of speed,
because curing can be very very fast.
It's basically a question of cooling the foil down.
Disadvantage of the UV curing glues is that it does take some time for them to cure.
And once they are cured there is a Y where the the process of three
keeps going on even after you start illuminating.
So they need a certain light dosage to
initiate the process and then they will cure for awhile.
Now we've seen how we take a material,
converted into an ink,
develop a printing or coding method for it,
and we take it, transfer it first through
some small piece of research equipment to a roll-to-roll process step.
Now discretely processed solar cells are more than sufficient for us.
It could have been in line.
Let's just assume that we,
in discrete process steps,
made all the layers in the stack.
We tested it, and finally packaged the solar cells.
This then represents the finely scaled solar cell
where the solar cells are available on a roll,
and on a simple roll like, for instance,
in this course you've been encouraged to acquire freeOPV.
On a hundred meters of foil,
you have more than 2000 of those free OPV modules.
And this means that on a small compact roll you can have many many many many solar cells.
A lot a lot a lot a lot of
single junction solar cells all prepared so that you can go and play with them,
learn from them, look at them, test them.
But the point is that,
with simple equipment, we can make a lot of cells with very little manual labor,
and there is really the advantage of the scaled roll-to-roll production
that with very little both manual labor and materials input and energy input,
we can produce a lot of cells in very little time.
For optimized inks, so where inks have been optimized for a given print for
a given printing process for a given machine for a given solar cell device,
the manufacturing speed can be very very high.
The freeOPV sample, for instance, you'll receive,
has a total processing time of just one second,
so it's very very fast in manufacture.
