Recorded Live Session I

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From the course by Technical University of Denmark (DTU)

Organic Solar Cells - Theory and Practice

640 ratings

Technical University of Denmark (DTU)

Organic Solar Cells - Theory and Practice

640 ratings

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).

From the lesson

Organic and Polymer Solar Cells

By the end of this module you should: -Be able to identify the different steps in the theory behind the solar cells -Be able to measure the efficiency of a solar cell -Be able to describe the different layers in the solar cell and understand their function -Be ready to argue for different applications of the solar cells.

Recorded Live Session I56:02

Meet the Instructors

Eva Bundgaard
PhD, Senior Scientist
DTU Energy
Frederik C. Krebs
PhD, Professor
DTU Energy
Mikkel Jørgensen
PhD, Senior Scientist
DTU Energy
Morten Vesterager Madsen
Researcher
DTU Energy

>> [INAUDIBLE] Okay, so now it's 12 o'clock.

Yeah, so.

>> Okay, thanks a lot.

Thank you all, for joining today, for joining the course.

We have probably approaching 20,000 students registered for the course.

So thank you for that.

The support has been overwhelming.

It's always been it's also been a pleasure to see you on the forum,

how you all contribute, and help each other out on answering questions.

Many of the questions that we could answer but

maybe we are not up at the time of their posts.

So it's great to see that you, you help each other out.

It's also great to see that the most of those who started are still following

the course, so, so we haven't scared you away yet and we are really happy for this.

The purpose of this session's, of course, to give you live on this try out,

this live session [INAUDIBLE].

We see they have, of course,

some small problems with sound, maybe video, who knows.

At least we'll record it and make it available in the end.

So, I say we start out and the way it is going to work is that [INAUDIBLE] is going

to ask some of the questions to us, to this panel which is Mikkel and Eva and me.

And once we've answered those, we will take any questions that you have and

you can type it to the box, and so, yeah.

Start out the big one, part of this we'll we'll run for an hour and

then we'll have to stop because, the time limits, an hour.

But we take as many questions as we can.

Okay so the first place we saw quite a bit in the forums is the reading

material I guess most of you already realize by now but just to clear it up

the course [INAUDIBLE] .com as well as links the syllabus in the weeks.

This [INAUDIBLE] webpage and this is mostly where you can,

where you can find our reading material.

And I'm sending in a full PDF doc.

Okay, so the first question we saw in the forum that we wanted to,

to look into is, what are the difference between [INAUDIBLE] and [INAUDIBLE] cells.

And also, what is it that makes such a big difference,

when we go from one generation, to the next?

What is it that makes solar cells sufficiently different from iii?

That it's a new generation, and that in,

in the end you can [INAUDIBLE] that makes [INAUDIBLE] the third generation iii.

>> I'll take this one.

Well, of course there's always a first generation and

that is in the case of solar cells was the first reincarnation of the solar cell and

that happened to be made from a crystal-, a block crystalline silicon.

And silicon is a, does not have a direct bandgap so

that means you need to use a pretty thick piece of material

to get enough of salt in, in the layer that needs [INAUDIBLE] to the sun.

And this of course is part

of the fact that this was actually a quite impressive solar cell type.

It had had the draw back you needed a lot of materials which needed the and

also you needed a high processing temperature and

could cut this material into a thin slice.

It's basically a rock solid and you cut it to this thin slice, a wafer.

And the idea was,

of course to maybe use something else that had bigger absorption, cross section.

And that you could make progress at a lower temperature.

And, and if all this [INAUDIBLE] he has this [INAUDIBLE].

And it's certain, certainly not an, an indirect bandcap and

a dierct band cap meaning that it's, as part of much.

But when the photon's, this,

this hitting, material therefore the ability of absorption is much higher.

Therefore, you can get away with using much, much, much thinner layer,

of of a more compared to crystalline silicon where you need a thicker layer.

A thin works, on solar cell.

And also [INAUDIBLE] it also show, turned to be impossible to make a thinner

solar cell possibly at a much lower temperature using much less material.

There were then other changes with with the [INAUDIBLE] solar cell or

the thin film solar cell [INAUDIBLE] second generation solar cell.

That's why people of course search for another, yet

another version version that didn't have some of those disadvantages of them.

There we came up with the organic sort of, third generation.

So all the different types of solar cell approaches that qualifies.

>> Okay and thank you the answer, Fredrick.

I think if you want the books and to have updates and.

First of all, why do the parliaments who use have the that they have

can exhumed them?

Why does this make this good solar cells also or why this fits the solar cells?

Or how do we what role does the solar spectrum play in all of this?

So I think it's, [SOUND] take that?

>> Yeah. >> [COUGH] Well, yes, w,

we can tune the absorption of spectrum color of the, the [INAUDIBLE].

that's one of the advantages you can tailor to,

to have any absorption you like.

Of course in practical terms it's it's not that easy,

but we do have methods to make either, green, or blue, or red color.

And this is, in terms of use, or usage, it's

a great relevance for tandem solar cells where you would ideally one part of iii,

one part of the spectrum whereas it's transparent in a different region.

And you want a complementary column too that absorbs let's

say in the opposite way.

If you had more junctions of course you want differently absorbing materials,

materials absorbing in several different areas of the solar spectrum.

Interest to, to have absorption in all the solar spectrum,

because that's where the energy from the sun is.

We initially of course go for

the area of the solar spectrum where there is most energy.

That is in the visible region and the, the near-infrared.

The solar spectrum extends far out beyond

4,000 nanometers there's not so much energy.

So the question is, what, how much effort should you

put in to design the material and how much energy can we expect?

This is currently an, an, an area of active research.

So I think that answers >> Yeah.

>> All the questions.

>> Thank you very much, and I can see you are getting some questions in.

Right after we'll try and save a little bit in our the questions here to,

sort of, try to accommodate that.

One question we saw was when you get your degree what can you do with it?

And so, I think on my part I can say

we have a technique, some experiments you can do.

It's still in Danish.

We are working on it's translating it.

[INAUDIBLE] but we'll will make this available directly.

Following that I don't think I think if some of you can say anything about

what we can do with a [INAUDIBLE] degree.

I think it depends on what kind of instrumentation you would have available.

If you will have the [INAUDIBLE] connect with a server and

go out [INAUDIBLE] But it very much depends on what

kind of instrumentation you have [INAUDIBLE]

within the that you have available

[INAUDIBLE] Also been working on my web page,

then we can document the things that you mentioned.

And we really encourage you to do that.

It's not available yet but it will be at some point.

>> Yeah, at some point.

And we had a follow up question, that we mentioned this on the phone.

Can I have a new label?

>> On the solar cell?

Yeah. >> Yeah, I mean definitely,

will move gently.

We don't, depending, we've,

we've shipped already, a few different types of, solar cells to you.

If you have a carbon based one I think the majority of people who will receive,

that have received it sort of all black, is no silver, all shiny,

[INAUDIBLE] all black, all red from the [INAUDIBLE] or blue.

And they are agreed.

The, this carousel does not like liquid water near [INAUDIBLE].

So if you try and steam off the label, I, I wouldn't recommend it.

I think you could get away with it.

Then, on a separate note, the the cell does not like sharp [INAUDIBLE],

it's quite a thin, so it's only about 100 microns thick.

And if you, it is possible to it sharp, if you do so,

you may risk de-laminating the two layers of the soil.

Basically two layers that are put together and

if you extend it tear too hard the label you may de-laminate the soil some.

So I think the odds suggest if you do in gentle, gently yes but a.

You may afford a risk at destroying [INAUDIBLE] And that's, I'm, I'm sorry.

We [LAUGH] that's data there, I cannot help, we cannot help you.

And so be gentle, that's all I'll say.

No sharp edges, no sharp things, no excessive [INAUDIBLE] Now,

don't dip it necc, necessarily in water.

I think it'll work, it'll short in water.

I don't think you can leave it there for long time.

We didn't test it, if you do it.

>> Perhaps we should also say it shouldn't be necessary to leave

it there because how could it [INAUDIBLE]?

>> Okay. So the next question that came in live is

[INAUDIBLE] On top of that,

I look at [INAUDIBLE]

>> It stopped with

the the commercial problems.

It has been several commercially initiatives.

The, you know, the, the majority of commercial activity

within the field of [INAUDIBLE] is linked to, material providers.

So the more companies that provide inks, or materials or shop component for

the organic source, these type of companies, are more likely to.

Grow to a to a size beyond determined by public funds.

Most of the people are trying to get buy materials where we are are academics,

studying.

So that means that they're a market for

this type of common use is 100% linked to nearly 100% or fully linked.

To the public funding of goal into [INAUDIBLE] use.

There has been a few companies where their, I should say, goal,

declared goal of making and manufacturing and modeling ODP.

One of best examples that [INAUDIBLE] went bankrupt in 2012.

There's also a company called Extronics that changed the strategy in the end,

for funding for solvency and is now acquired by SunWave, and then

there's been a few other small companies, and I think they are starting to survive.

There's, a real answer to the, these regulations.

And if something isn't correct and it's taken to a company is.

So these companies, if they are in existence for

much longer they will, are fully linked to investor demand.

And the answer of course, is that OBE is an under performer.

It's not good enough.

To compete with other emerging technologies.

Solar cells are not good enough.

Yet.

Certainly not the old way, silicon and maybe solar technologies

could potentially compete, but they still rely heavily on subsidies.

So public, subsidies in use.

[INAUDIBLE] many, many,

many different ways of recording

people just using [INAUDIBLE] No?

Yeah?

[LAUGH].

Okay. Another question about [INAUDIBLE].

Basically, how do you [INAUDIBLE].

What is [INAUDIBLE]

[INAUDIBLE] [COUGH] Of course it's

been something to [INAUDIBLE] it depends a lot on the way

this decision is [INAUDIBLE] in principle we can, can work and

if use like better than some of the Earth and [INAUDIBLE].

But today Egan Chris from I.T. works quite well.

And a huge line to overpass I, I, still think that the the organic technologies

has the potential to poll really well in in Grade A where it's 100% accused line.

But in just looking at margins it's it's not as if

there's no magic area you have to suddenly make.

The world of energy new technology.

You are looking at.

And this could be a competitive edge, for sure,

but it's not going to make up for, a low efficiency or

the low efficiency that ["OPD/g"] has today when you compare to.

>> I was going to say, there is an aside to that question.

[INAUDIBLE]

>> That's a good

part, I think that's also why the other parts raised up on

the partial shading and maybe we should take that down.

>> Yeah. >> Yeah I mean

to me it's different [INAUDIBLE].

A real shock to Jonathan.

So its, if you shower it really, really kills the, the [INAUDIBLE] forms.

[INAUDIBLE] About to die, therefore had a shadowing,

much much better than the, typical PM function type so it's.

[INAUDIBLE] Okay.

You have a new question from which is is there

any negative reactions related to the [INAUDIBLE].

Yeah, I mean absolutely.

[COUGH] Actually, the some of the, you that receive.

Some of you who received the sample have received the cells experiment where

we work on a very very low cost material that has ten teacher forms problems.

And you can actually see these problems in the.

And, especially when you should take this type of solar cell to a heat cycle.

You will see the grow.

And when the grow, they won't eventually eh, induce failure, eh, in the,

in the device.

So if you say that, here the device fails,

it's not because the solar cell material stops working.

But because a, should say.

The defect in the manufacturer.

Shortcoming in the manufacturer.

So you got excess to low cost barrier.

And it had the deficiency of these bottles that really needs cycling.

Because leads to this gradual growth of problems

that causes failures to the device.

Due to inoperation or delamination or other things.

So in that case, that type of solar cell would be very sensitive to heat cycling.

The OPV in general is not, it would not like higher temperatures.

So the higher the temperature, the faster the degradation reactions are.

Generally a, a chemist would look at any chemical reactions.

And say that they would increase the temperature ten degrees

any reaction taking place is increased by a factor of four.

That's a very rough rule of thumb.

At least if you go up by ten degrees we have a process that is happening in there

that may be a to start the process.

[INAUDIBLE].

We generally see this in addition to this style of course.

Although, effects the solar cell efficiency probably [INAUDIBLE] has

an glass position temperature, something like that.

If you passed that then of course is a totally different rate machine.

In terms of degradation that you get access to.

In generally means that when you increase temperature, degradation goes faster.

Cycling effect on, on thermal expansion and contraction is also more significant.

But it's more linked to mechanics.

The mechanical failure of the parts rather than,

than changing chemical reactions due to increased temperature.

You can always say that above 65 degrees OPV's start to see or

demonstrate faster degradation.

>> Perhaps add to that, that you have to have examples of solar cells placed

outside in Denmark where there are great cycles of temperature.

>> Yeah, we have samples of those two years outside where they're

still operating beyond T80.

And, and we also have the devices outside now since 2009 of course they've

degraded substantially, but they are still there.

Of five years on, and they're still operating.

But not, not at, not anywhere close to the, the starting point.

But they are still, they are not dead.

They, they are still, still possible to extract energy from five years on.

So, you know, thermocycling from day and night.

Day and night, and it's possible.

>> Okay, we are a lot of new questions coming in.

I think one that can just quickly answer this.

How many OPV facilities, research facilities are there in the world?

Eh, I can see here Andy's mentioning [INAUDIBLE] our place in Denmark and

Frankfort and Melbourne.

The, if you I think you answer is in terms of wall to wall

manufacturing capacity or I think.

>> Just in general.

>> If you take laboratories I mean it's an enormous amount.

I mean especially in Asia those,

my guess is there are thousands of laboratories in the world.

That has the capacity to make organic sources and they do it regularly.

It doesn't you're actually [INAUDIBLE] those

people who at one point Academics will make a study.

Where they're looking at something and

at the OPV the solar cell device is one way of studying some other materials.

So from that point of view they are a lot of them.

So my guess is a 1,000 at least worldwide.

>> For large scale?

>> There is few.

>> Very few.

>> So if you are looking at all 20 people that actually,

maybe there's 20 labs that, that claim to be able to do it.

And maybe they have people who really can do if you came with a shotgun and

then say do it now.

There's probably very few labs that can do it.

Just like that.

Okay?

At least one.

>> [LAUGH] >> Yeah.

>> Well, we still have a lot of questions in here.

And so one we can take now is.

How would this, a organic solar cell work with one wave length,

short wave length so basically how much effect can it have?

>> I think both that, but

also in general what can we do to may be extended solar cells and so on.

>> I think, I mean, well, the free OPV that, that's been sent for

the Coursera courses.

Harvest for about 650 nanometers.

We regularly make it and some of you will received these more green polymers.

More people have received the red, red one.

This, [INAUDIBLE] ship the blue and the green and

they go to maybe about furthest out maybe about 800 amperes.

Now, Eva here in her heyday made all the way to 2,000 nanometers.

The difficulty that you often use voltage [INAUDIBLE].

At the moment I would say that going much

beyond a 1,000 nanometers is actually quite cheaper.

Okay, another quick question.

Since it's of course, a big investment to start out with,

factories that can, when manufacturers go into those own solar cells.

It will be possible to retrofit em, existing plans that,

that draws off the plan.

Eh, I guess that's basically the question.

Is it possible to retrofit a plant that makes other printers.

>> So that they manufacture OPV?

Yeah, absolutely.

You need print, a printing machines.

Of, of course there are several different processes we've developed many in

the past.

Different process types, different machine,

you can do onscreen printing, there's a lot more [INAUDIBLE].

I'm sure you if you made an error or something,

it's a question of what machine do you have available.

It's certainly possible to tailor it inks and process so

it matches your machine, but this can be done.

We've done it several times.

>> Another question, unrelated,

is, relating to civility now,

what is the average working night at OPV.

>> Average, [CROSSTALK]. >> Eh, I mean, it, it depends, a lot,

on the purpose.

We do testing outside of, of the landscape.

And there we put significant effort towards packaging

the source of what this is really what matters when you go.

When you really want solar cell [INAUDIBLE].

It inherits the abilities of technologies.

It's on the order of several years.

May, maybe as much as eight to ten per day, if packaged correctly.

So it's all about packaging correctly.

And then not introducing errors when you install.

So you have to think a lot of how, how, how you, how to affect,

how I'm going to install it, how am I going to handle it on the waits list.

If you do that correctly.

We're looking at several years, as we demonstrate.

But, for instance the free OPV that we shipped to you.

I mean, I have to admit we are not going packaging.

because there is none.

And I'm sure these will effect it, there will be the delamination at edges.

And that, that for

some of you unfortunately will lead to a past interest.

And then, for others, that's also part of the experiment to see how,

how far can you push it.

So, so, the answer is if, if you know where you want to go, you,

we can access any areas.

But then, you have, you have to make the effort.

>> And also, it depends on the materials used and on the outset,

working with solar cells, with all of the layers in the cells.

We'll learn more about this in Group 4.

You'll have to wait [LAUGH].

>> Yeah okay, a question that's coming in here is

probably about MCA efficiency defaults.

I think we can extend this to say,

say something about the differences between the generations of photo cells.

So what is the full energy feedback time compared to different generations?

Are there limits in practice for

the different generations that others don't have?

I think,

I mean, it is a part of the [INAUDIBLE] >> [INAUDIBLE]

>> [INAUDIBLE]

>> Last week, [INAUDIBLE].

>> [INAUDIBLE] [CROSSTALK].

>> But, generally, NCA is, if you, of course, it's a very complicated

diagnosis that some of you made rather challenging, and it certainly is.

But if you step back and you re-look at what it is, it is a housekeeping exercise.

And often can be equated with either housekeeping or an advanced

banking system where you exchange current rates between different monetary systems.

And you have to add all these things.

Some numbers you can add, some you can't.

And the actual mathematics behind is not that complicated.

The amount of numbers that enter the equation is enormous.

And if we step one, one step even further back, it is even simply

using as little energy as possible in the tubes that constitute the solar cell, and

in the process of turning these materials, these raw materials, into a solar cell.

And, you know, the simplest, the fastest answer that goes

without saying is use something that we have a lot of, so for

instance, or diamonds, or whatever that we have little of that's expensive.

Use something that is really, really accessible.

Use very little of it and when you make it into a solar cell, make it as simply,

as quickly as you can using as little energy as possible.

That's is all [INAUDIBLE].

If you find or identify a process and

a solar cell that scores high in these areas, it's bound to have a short.

Take a first generation type like where

you have to purify silicon at very temperature.

[INAUDIBLE] Encrystalize in a particular way.

There you get a very very nice [INAUDIBLE].

Getting it.

The advanced solar system [INAUDIBLE] organic also [INAUDIBLE] throws us off.

You can get everything with very little temperature.

So, eventually, you can dry organically [INAUDIBLE] turn up the heat.

So 100 degrees or

140 degrees still low temperatures compared to most of the second generation,

other second generation sources are hundreds of degrees.

So there, we are lower in temperature, the solar cells are thin,

the field of view you see is about 100 microns thick.

[INAUDIBLE] minimalistic, so

you could say that already in you [INAUDIBLE] you

have a lot of weight, a lot of material there and

[INAUDIBLE] energy embodied in it, both in itself but

also in the process of [INAUDIBLE] to the world.

And so, and this is really what [INAUDIBLE] is all about.

Keith Matill uses [INAUDIBLE] to make sure that [INAUDIBLE] and move fast.

Yeah? >> I think that was a good, good answer.

Let's see what I have on my list.

Oh, yeah.

There's one, one important one here.

Of course, many of you ordered the [INAUDIBLE] solar cell.

And I can see [INAUDIBLE] web page that

many of you would like to [INAUDIBLE] this article is [INAUDIBLE] access,

but I think [INAUDIBLE] >> Yeah.

I'll try this afternoon [INAUDIBLE] if it's possible to urgently get it paid

[INAUDIBLE] open access.

Of course, it's a little erratic that the source says, free, and

then, you have to be subject to extortion to actually read about it.

And this, of course, we'll have to change.

I'll see if I can get this changed this afternoon or

how soon we can actually get it on market.

Hopefully, the next session, the.

>> We have parts of [INAUDIBLE] I think that would be possible.

>> Yeah. >> And then, certainly,

also, when we have this for the next session, we're contemplating doing it, so

we, each time we address different time zones.

That means, now it's comfortable European time for us.

[INAUDIBLE].

>> We found already.

>> US time?

>> Three o'clock local time, yes.

>> [INAUDIBLE] If you have any wishes for

this live session, please just put it in here.

We've loaded our hopes on the form of.

Not India right now, I would say.

But the piece arriving, what would be your preferred time?

Are you up in the middle of the night to follow this right now?

How's this working for you?

>> Well, I think we are on the way to running out of questions here.

So, we welcome.

If you can answer more in the chat box here.

Otherwise, I will continue with that, I'm asking a few questions.

If you think your questions are, looked over,

just posted it again because it's a little bit hard to keep up.

Yeah, so this one new question here is that any reduction in efficiency with

the solar cells happen, except for the, if you measured it out.

I guess this is probably if you want to put it on the roof tiles

you have the solar cells probably on the curvature of the roof.

Will this have a negative effect?

>> As long as you don't delaminate the cell is quite fine in the version,

you see, so it can certainly be formed over a curved dome.

It should be only cylindrically curved so one dimension, so

2D curvature, I [INAUDIBLE].

>> [INAUDIBLE]

curvature of a pencil

[INAUDIBLE].

Aside from that, we should be able to do it million dollar

many times at least [INAUDIBLE] it into some [INAUDIBLE] and leave it there.

Costs compared to [INAUDIBLE] maybe, you will only, you will start the [INAUDIBLE].

And this is a, normally, a catastrophic failure that means

the cell is really significantly reduced in performance.

And as a side effect,

one should have elimination to have actually a void formed inside the device.

And there you can [INAUDIBLE].

Even if it still works out [INAUDIBLE]

be more quickly degraded [INAUDIBLE].

Basically, what is the largest [INAUDIBLE] using

the materials, and can they be processed into,

basically the question is is the problem

that [INAUDIBLE] and he also asks [INAUDIBLE].

That happened.

>> Well, the answer is yes to all materials we have remaining.

I mean, as long as you can just the material

can support the solid that we use, then it will work.

We should just say, that in the week three,

we're learning more about the materials.

And also here, the size of the material and how to make it link.

And also in week five, we learned about how we produce.

So, there's a lot of printing methods in that week as well.

I think the present article relates a little

bit to the question I had from the forum,

which is basically, can we do it?

>> Yeah, why.

[INAUDIBLE].

>> Yeah, he can do that. If the supports the you're using

[INAUDIBLE].

And regarding the DIY source, we actually did that long ago.

In 2008, we made a lot of for a music festival.

We handed out what was in modern.

So that's about the, yeah, that's about six years ago.

And this type of package.

If we ship off a few people [INAUDIBLE].

People can really pick it up, and then basically, you can check it out.

There basically you can [INAUDIBLE] touching stuff,

and then, maybe wear gloves [INAUDIBLE].

Of course, you know, going into the supermarket and buying stuff or

making a out of this, I think would be a little the future.

If not, you always need some special chemicals.

You need need need stuff that is not.

It's not impossible to get a hold of these tools, even through the outside.

I guess one [INAUDIBLE] would be [INAUDIBLE] about

the [INAUDIBLE] because the [INAUDIBLE].

>> [INAUDIBLE] They could purchase one of those hats.

Well, not really.

>> [LAUGH].

>> Okay, I think good exercise.

[INAUDIBLE] Again, for free.

Everything we do is for free.

And they were, I think they only made 2,000, and

they were all given away at the.

So. >> Yeah.

>> Maybe, I mean, I can go away and take my own personal product, and showing it,

bringing it into the session.

I can show it, so it doesn't.

>> [INAUDIBLE] Student in the video industry.

>> Yeah. [INAUDIBLE].

>> At the end of week, you will be seeing more of the applications.

[INAUDIBLE].

>> Saw it already. >> [INAUDIBLE] I wouldn't say it's old.

But it's certainly its many years.

[INAUDIBLE] If we don't receive that as an application, you know?

>> There's a guy asking if, well, we just give them away,

they want to purchase it, then why would we do it that way?

>> Well, if you have to understand that this, we,

our job is to develop technology.

And a very essential part of developing technology is also

demonstrating technology.

So you show that it's, it can transcend beyond imagination and

[INAUDIBLE] lofty ideas.

So, we actually, we can materialize our ideas

into a bunch of forms and the solar [INAUDIBLE].

We were sort of young back then.

I wouldn't say, we needed the money, but we certainly needed to show or

wanted to show that.

So, and so can actually work in.

So, what [INAUDIBLE] with our interest.

And then, and, and found out where with the sort of technology we have,

we can say that it is a boundary condition to this experiment.

Was that we can only use screenprinting, flatbed screenprinting to make the device.

But that means you have to unveil a new process that you [INAUDIBLE].

There was to me a very steep [INAUDIBLE] managed to do.

And it was a very pretty circular, concentric set of connected solar cells,

I think we needed an application for it and this has limited performance.

And the [INAUDIBLE] and charge the battery.

And since it was for a music festival,

[INAUDIBLE] put in a hat where we believe that would have it.

And most of the time, if it's on top of your head and starts to go up and move,

expose yourself to the sunlight.

Whereas, if you put it in your pocket where your mobile phone or something.

He reckon that it wouldn't be [INAUDIBLE] as much as it could.

So that we put a lot of thought into this demonstration, and in the end,

it turned out that the solar cell was actually the quickest thing to realize.

Most of our time was spent putting solar cells into hats, and

fixing radios, and these things.

So, we learned one very important lesson in the, when you think

about demonstration, make sure that most of the effort you are putting

into the demonstration actually goes into supporting what you're good at.

I mean, I have, we have no real experience with hats or radios, so we were,

you know, looking for hat radio people.

We would all got sources, so this is, I hope this answers the question, so,

yeah, it was a learning process for us, too.

And, I think our main conclusion was, it was great fun, but

we wouldn't do it again.

So, that's why I cancelled it, or we cancelled it.

Yes. And,

I think we just coming quickly back to this DIY, or [INAUDIBLE].

And, I just quickly mentioned [INAUDIBLE] in advance,

there's a link to the video, and there's another online.

So basically, you can make [INAUDIBLE], say something about that.

That's a different technology, and it's overrated.

>> Yeah.

But it's the personal type solar cell is a magnificent example

of a solar cell as first described in around 1990-91.

And then, and

it came out of 11% before, so

then now 25 years on it's never

really been demonstrated.

In fact you've, and you, even though it's one the most popular scholars out,

if you can very easily get a hold of the materials titanium dioxide [INAUDIBLE]

using paint [INAUDIBLE] everywhere storing the [INAUDIBLE] dioxide glasses.

Get to a, from a, [INAUDIBLE].

Anything that will color this titanium dioxide will sensitize it,

and you can a functional solar cell with very little material.

It's a very simple solar cell [INAUDIBLE].

It has some [INAUDIBLE] like in its [INAUDIBLE].

I think when the [INAUDIBLE]

really and

most often it's,

it's most current

form it's [INAUDIBLE]

to seal up for operation

of the menus [INAUDIBLE].

Yet I'm basically running out of questions and

the rest, but there's a few more in here.

[INAUDIBLE].

Yeah, one thing we could just comment on a little bit is one of

the assignments this week was and and

describe some applications you could imagine with photo cells.

And we can see in the problem, that, that many,

many of you are already I think just over a hundred post already.

So we really.

And I think this is also one of the,

the, the things that we were really getting out of this course is,

we can use you to generate ideas and we're definitely looking at them.

And many of them are really.

I don't know if you can add something to this.

>> The video is unlocked.

Yeah it is unlocked.

So basically, there are many, many different applications for

this sort of thing.

Or you can use contact to the limitations in the technology in order to,

to make up applications.

So I think you, generally you've been really good at this.

[INAUDIBLE] Take around and

[INAUDIBLE] each of you and

then have you say what

is your, if you would.

Say there's a critical issue that we need to address.

What will it be?

Will it be materials?

Will it be printing?

Will it be to have with this device.

That's why I make it.

What do you think is the most critical aspect right now and the weakest?

>> The critical aspect what are the relating issues.

It could be that

[INAUDIBLE] okay,

it depends on

what you want

to use it for.

I certainly think that we should [INAUDIBLE] to increase efficiency.

But if,

as according

to [INAUDIBLE],

most people

do this for

[INAUDIBLE].

[INAUDIBLE] I would say there are many,

many things that need to be developed still.

I mean, but I also do think that has now reached a.

We can transmit it, your [INAUDIBLE] and not over.

You will receive information which means that it can

actually be manufactured quite [INAUDIBLE] all and in [INAUDIBLE] form.

Can be shipped around.

It works outside our laboratories.

May, maybe sometimes not always as well it should but.

It is certainly, the move from, to say,

an illustration of a vision.

To being an object that exists, and there can be many variable to many.

Which is true to the original being art.

There are of course a few rough corners that need to be

wound up being that mentioned efficiency and stability also.

You know that, that is certainly critical issues.

Manufacturability, the costs the, from my side if, if you look at the LCA,

the thinner, the finer you can go, the less you can use the better.

And that is really I think what is.

What it's all about,

making sure the components you have are simple in the operating.

You could have a very nice ink, if you spend [INAUDIBLE] synthetics that make

the, you will to make this material generate the type of chemical waste and

I don't think anybody wants this.

It will be a lot more interesting to have a, a chair that is.

Maybe even half of,

much less of half efficient making while generally more distance, more.

And this is something that is not in, in, in, in the equation, but

we know this because, we do it with significant states.

So, we can see all these problems that arise suddenly.

The barrels of waste we will have.

If we made the irrational choice, we went straight for a high efficiency

we got this of consequence for the globe.

So, I think this is maybe this holistic view of making a choice sustainable

version of the rule, whatever that may be.

Maybe it's only a 1% effiecient source or that it's.

It's truly, I'm not sure it's much more

interesting than 10% source over there.

>> Yep, well I would say stability for sure.

We need to have cell that's much more stable.

So, if you pay back the energy you put into it.

Or several times than just one or two.

That are going to compete with other technologies.

There it seems [INAUDIBLE].

>> Yeah.

>> Okay, thank you very much.

I can see that we have a few technical questions in the end.

And that's very fine because, you know, there are already some.

I think that's basically answering it, and I think that will get,

folks are welcome to ask, these technical questions in the forum.

We can try and answer some of them,

there are many of your fellow students that are really good at answering them.

[INAUDIBLE] What I would like for now, is all of you to go in there.

Discuss with each other.

And basically have that learning experience.

So as the forums are running right now.

Please quiet that.

>> Can answer that more than anyone Rachel.

>> Yeah.

>> Hm, you guys cannot answer my question.

[CROSSTALK].

>> Opening [INAUDIBLE].

Basically is it, is it practical to incorporate

[INAUDIBLE] I guess it's impossible to have some sort of,

I think we could both be codings or [INAUDIBLE].

Because, they make this [INAUDIBLE].

>> Yeah.

I mean of course, I mean the,

there's no, normally no magic in, in, in the real world.

>> It's too expensive.

>> And, and the, if you're thinking about this [INAUDIBLE] putting in gold now,

see solar cell.

It's been demonstrated a few times.

And considering the effect's have been shown.

When you come to practical manufacture, and the, you know, if,

if you're just seeing a one out of 5% increase in your performance.

Compared to the hundred percent didn't [INAUDIBLE] in, in instability, in.

Reproduce a and all these things may,

maybe sometimes you're better off not doing these things.

You want something, to be robust and stable and

generally applicable if, if circuited absolutely.

But a lot of the time it's, should we say a physical fact,

physical phenomenon that are in operation, and

you can document that they are in operation.

Thru measuring of [INAUDIBLE] peak performance and

whether it is useful in a-.

That is not normally the qu, the way are, questions like that are answered.

And I think to our knowledge for

when people come up with these of course we try.

We don't have a most of the time it's not working.

Or it's not worth the effort.

>> [INAUDIBLE].

>> Yeah, of course.

>> [INAUDIBLE].

>> It's not because it is now,

it's all good because it's now [INAUDIBLE], it's inspiration.

Maybe a nano to micro size [INAUDIBLE].

And it is possible to print these inks because of the nano would,

because if it wasn't, it wouldn't be in suspension,

we wouldn't be able to print it and make it stick together.

And they are again, you can behave like solid liquids,

once we tried so certainly there is a lot of nano inside of me today.

So we use it when it's useful and when it's not, we, we don't use it.

So, so, I think the answer is if it makes it better, we do it.

>> Well, yeah, okay, another question that, that came in was basically

is there any way to make contemplate existence to increase the efficiency?

I think there's even a specific example from Garrett,

he says, if you submerge the things that may not be such a good idea if you

generally this concentrated system is a good idea.

>> I think if you can prove, concentrated systems are certainly a possibility,

I mean you more than the whole should know

you made a PhD in concentrated light for OPV.

And then for OPV interestingly the the maximum performance and

concentration is typically low concentration.

They seem to perform as a general rule,

maybe slightly better in three songs than in one song.

Some of them maybe have ten songs.

They certainly have already have 200 songs it seems like

too many trouble with the heating.

Of course, it's virtually like that, it's certainly an idea.

And I don't think is a problem.

I think you really wanted to do good things that, that so

he's called an interesting, an interesting point.

>> Certainly, I guess we could mention as well that I guess one of the reasons that

question is popping up is because when you see these storm breakers as these.

They're typically measured at a really really high concentration.

That could be at fault and it sucks.

And, and it is a really expensive [INAUDIBLE] really

getting a good [INAUDIBLE] yeah, exactly.

>> If you put a lot of materials into the structure surrounding the solar cell

the solar cell suddenly becomes a little

part of the over all systems cost with the mirrors, the tracking system.

You have to remember that concentration,

especially if it's point focus based concentration, only works with track.

So the moment you are not m, you are focal, focusing system is not looking

at the sun, you won't get any power from that.

That also means that if it's diffused by the cloud it won't work at all.

So you can only put this in an area where the sun always shines.

And you can come, fall easy pray of

having to clean your system.

Then, of course, you could have more cylindrical focusing system,

where you [INAUDIBLE].

This is, still needs some form of tracking but

not as complicated form of tracking and as, so,

generally the word is that a concentrated system is not as,

financially at least, an efficient, as efficient option

as centered, stretching out a piece of foil, or.

>> I guess [INAUDIBLE] basically the same eh,

consideration that's yeah [INAUDIBLE] basically we supplied some.

So, I think that's sort of a general agreement we have that works.

Probably not the way to go [INAUDIBLE].

>> The way I view this is that what I find interesting is that I have,

what I find interesting is that it, I think the world record now

is way over [INAUDIBLE] to maybe 50% power conversion [INAUDIBLE].

These experiments show that it is possible to take sunlight, okay,

you have to concentrate it and do stuff to it, make a few 1000s suns you have to

[INAUDIBLE] but it shows that it is possible.

Take sunlight, convert it into electricity at very high efficiency,

I think this is the main outcome of these experiments.

If you want to do this for money and do it in such an environmentally

responsible way, I'm sure solar power is.

I'm not going to, it's hard to say that it's impossible,

but I'm going to say that it's faced with challenges.

Monetary, that are, you know, maybe wouldn't put on the top of my list as

as a search topic for like, [INAUDIBLE].

Okay, I think we're about to rounding out the slide questions now.

And just before we do that I'd like you to put into the common field if

you had good audio, bad audio, if you thought about it.

We can go through it and

see how many there were, or satisfied with the policies.

Next week we will try and

improve it, we've ordered you a webcam equipment and new microphones.

So hopefully we can do a lot better.

My thoughts have been the connections.

Maybe we can go gets some other leads instead [INAUDIBLE].

And if, if you have any suggestions for this,

you are more the welcome to [INAUDIBLE].

I don't know if we have any closing remarks we'll be there again

>> Next week.

>> Absolutely, [INAUDIBLE] Money.

>> Yes.

[CROSSTALK].

To be seen.

>> And I'll just take the twitter, actually,

I don't think we have any questions in there.

Yeah, okay, so we don't have any questions there yeah, so thanks everyone.

>> Yeah, thanks, see you in a week.

>> [NOISE].

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