Episode 16      19 min 38 sec
The Leap from Frogs to Plastic Solar Cells

Prof Andrew Holmes of Bio21 Institute recounts how a poisonous South American frog inspired research into development of plastic solar cells.

Guest: Professor Andrew Holmes from the Bio 21 Institute

Topic: How the poison arrow frog inspired research into plastic solar cells.

"What about shining light on the plastic? And getting electricity back out from it? And indeed it is possible." - Prof Andrew Holmes




           



Prof Andrew Holmes
Prof Andrew Holmes

Professor Andrew Holmes. Andrew is an ARC Federation Fellow and the inaugural VESKI Fellow at the Bio21 Institute at the University of Melbourne.

Andrew Holmes was an undergraduate at the University of Melbourne and completed a PhD degree with Professor Franz Sondheimer at University College London. He worked as a postdoctoral fellow on the final stages of the synthesis of vitamin B12 with Professor A. Eschenmoser. He was at Cambridge for thirty-two years, then moved to Imperial College from where he is on long term leave of absence seconded as an ARC Federation Fellow and Inaugural VESKI Fellow at the Bio21 Institute in the University of Melbourne and CSIRO Molecular and Health Technologies, Clayton.

Professor Holmes's research interests span a range of natural and non-natural synthetic targets. His polymer research spans a range of functional and electroactive polymers. A recent interest has been the use of phosphoinositides to probe downstream signalling processes in protein kinases that has revealed many new proteins involved in intracellular signalling pathways. The work of his group on polymeric light emitting diodes has excited considerable attention and spawned a totally new research area. Further potential applications of conjugated polymers in the fields of field effect transistors and solar cells are also possible.

Professor Holmes is a co-recipient of the Descartes Prize 2003. In May, 2000 he was elected FRS. He was appointed AM in the Australia Day Honours List in 2004 and he was elected FAA in March 2006 and FTSE in November 2006. He was Chairman of the Editorial Board of Chemical Communications from 2000-2003 and he has been an Associate Editor of Organic Letters since April 2006.

Errata: The original audio contained an error. That error has been corrected, and the audio files have been replaced as of June 28, 2007.

Credits

Host: Dr Shane Huntington 
Producers: Kelvin Param, Eric van Bemmel and Dr Shane Huntington 
Audio Engineer: Dean Collett
Theme Music performed by Sergio Ercole. Mr Ercole is represented by the Musicians' Agency, Faculty of Music
Voiceover: Paul Richiardi

Series Creators: Eric van Bemmel and Kelvin Param

Prof Holmes' portrait by Michael Silver

Melbourne University Up Close is brought to you by the Marketing and Communications Division in association with Asia Institute.

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The Leap from Frogs to Plastic Solar Cells

VOICEOVER
Welcome to Melbourne University Up Close, a fortnightly podcast of research, personalities, and cultural offerings of the University of Melbourne, Australia. Up Close is available on the web at upclose.unimelb.edu.au That!|s upclose.u-n-i-m-e-l-b.edu.au.

SHANE HUNTINGTON
Hello and welcome to Up Close, coming to you from Melbourne University, Australia. I!|m Dr Shane Huntington and today!|s topic is solar power. Without question the single most urgent issue today is the impact the human race is having on the climate of this planet. We have become so advanced in our needs and desires that our actions are threatening the delicate environmental balance that sustains us. The need for energy and the shortcuts we are willing to take to get it will usher in a disgraceful level of species' extinction within our lifetimes. In Australia, it is often noted that we have an abundance of coal and nuclear resources. Of even greater importance is our abundance of choice. Australia has extensive scope for renewable energy generation with particular emphasis on solar and wind sources. Today, on Up Close, we are joined by one of the leaders in new types of solar power generation, Prof Andrew Holmes of the Bio21 Institute. Welcome Andrew.

ANDREW HOLMES
Hello Shane.

SHANE HUNTINGTON
Now, I want to take our listeners on the journey that you have been on. It is quite extraordinary and it started way back, before you got to Melbourne, in quite a different area. Now, I know it as being related to the South American poison arrow frog.

ANDREW HOLMES
Well, that is absolutely right, but I!|d like to step back a little bit and explain that I!|m a, what I!|d like to describe, as a pot boiling synthetic organic chemist. That means, in simple language, we like to make molecules based on carbon. And of course, these are the building blocks for the pharmaceutical industry and that was the kind of chemistry that has motivated me for a lot of my life. And it turns out, that these poison arrow frogs in South America, make a specific molecule that blocks signals through the nerve muscle junction. That is why they are poisonous. And, they are now a protected species in South America. So, there was a really good motivation for making this poison arrow frog venom because the frogs were now protected, it couldn!|t be collected from natural sources. It is an interesting molecule. We had to make it. So that is where we started.

SHANE HUNTINGTON
I guess we don!|t really hear that much about frog attacks. How do we know that it has this particular poisonous venom?

ANDREW HOLMES
Well, this one is not the most poisonous in the family. It might get a mouse. So, it was safe enough for humans to collect the species, extract this material from the skin. And study it and analyse its biological properties away from people and animals.

SHANE HUNTINGTON
This led to plastics and this is where I know a lot of our listeners will have trouble finding the bridge between these two, so, can you go through that? How you went from frogs to plastics.

ANDREW HOLMES
Well, those of us who are pot-boilers, like to make molecules. Now, usually, when a reaction goes wrong, it makes a polymer, or in simple language, a plastic. And we used to throw that sort of material away because it wasn!|t very interesting. But one day, when we were trying to make these kinds of materials, the person working with me was smart enough to recognise a very interesting change in property, when this so-called plastic formed. He didn!|t mean to make it, it formed spontaneously. And we were stimulated to follow up the properties of this material, which was related to the frog venom, in more detail. Specifically, this was a very special kind of plastic because it was transparent in one kind of light, but if you turned it over, 90 degrees, it was a different colour. And that is a very interesting phenomenon, related to polyacetylenes.

SHANE HUNTINGTON
So this is similar structure, similar material to the plastic bags we see, the chairs we sit on, the dashboard of our car, but in this particular case being related back to the frog venom. There were a number of properties that were very specific to this plastic that you weren!|t seeing in other plastics?

ANDREW HOLMES
Yes. Plastics in general, the same repeat unit, perhaps a hundred or even thousands of times. And that is what gives them their strength and their ability to act as insulators. That is how we stop ourselves from getting an electric shock, with electric cables and so on. But this particular kind of plastic was made from building blocks which were unsaturated. If you think of polyunsaturated fats, it is the same kind of principle. That is the molecule doesn!|t have as many hydrogen atoms in it, as it could have if it were fully saturated. And when it joins up with other units it leaves, what we call a polyunsaturated plastic. So, back in the 1970s a group in the University of Pennsylvania, led actually by a brilliant New Zealander, called Alan McDiarmid, who has recently died, were the first people to discover that these kinds of plastics could conduct electricity. So, this was a fantastic paradigm shift. People using plastics as insulators and yet, this lot found that they could be made to conduct electricity. And they were awarded the Nobel prize in 2000 for that discovery. That!|s what really started the field of these kinds of plastics.

SHANE HUNTINGTON
So, you have an amazing scenario here. You have a frog venom leading to a particular type of plastic that has very unusual properties. Now, my understanding, though as well as in addition to conducting electricity, which as you say is in itself quite mind boggling compared to what we normally see, these things can emit light.

ANDREW HOLMES
Yes, well the full story has always got lots of explanations in between. We discovered this plastic by accident. We met a person in our laboratory in Cambridge in the UK who encouraged us to follow this up and that led to an introduction to a physicist in Cambridge who was using these kinds of plastics as transistors. And so, a whole series of events brought us together. And then the final clinching deal was the British funding agency !V the Engineering and Science Research Council !V called for a multidisciplinary collaboration between physicists and chemists, in a new initiative called the Molecular Electronics Initiative to explore these kinds of plastics further. So we found each other through a total accident. Through serendipity we got together and started looking on these plastics that had emerged from the frog venom and one day, one of the physicists was using one of these kinds of plastics and now a slightly different one from the one we started with, and he put an electric charge across the film of the plastic and it gave out light. So, this was now a million miles away from what we started out to do.

SHANE HUNTINGTON
Yeah.

ANDREW HOLMES
An example of genuine serendipity.

SHANE HUNTINGTON
And I guess, there are now circumstances where that plastic is being used? Presumably it is not yet in our plasma televisions, but I guess there are a lot of simpler, I guess, examples of where light emitting plastics could be highly valuable.

ANDREW HOLMES
Absolutely enormous. Well, the day that discovery happened, we dropped all the plastics emerging from the frog venoms and became experts in light emitting plastics. We between us, probably filed about four patterns in that first year. We were the only people that knew about this phenomenon at the time. The world was our oyster. And we just had the opportunity to mine intellectually and academically fascinating project, but also to take forward the protection to exploit it in the market place. And, we went forward, and founded a company called Cambrdige Display Technology which was eventually floated on the Nasdaq in 2004. One of the dreams I had was that I would never have to write another research grant proposal and it would fund my research for the rest of my life.

SHANE HUNTINGTON
Has the dream come true?

ANDREW HOLMES
I!|m still writing research grant proposals. But, to answer your question, of course, if you think about sources of light, there aren!|t many sources of light in the universe that we know of. Most of them are based on chemical energy or passing electricity through a wire and making it get hot or by fluorescence and so on. We!|re making these plastics fluoresce by putting electric charge through a thin film. You can think of it as a plastic sandwich if you like. The bread is the electrodes, and if one of the bits of bread is transparent, we hook a battery up to the bread on the sandwich and the meat in the middle is the plastic that gives out the light.

SHANE HUNTINGTON
You!|re listening to Melbourne University Up Close. I!|m Dr Shane Huntington and today we!|re talking with Prof Andrew Holmes about solar power. Now, Andrew, it is one thing to produce light from electricity, but it is a whole other ball game to produce electricity from lights, so let!|s go a bit further along this journey and consider that possibility.

ANDREW HOLMES
Well, many people have asked this question so it does come to people when they hear putting electricity into thin films of plastic and getting out light: what about doing the reverse? What about shining light on the plastic? And getting electricity back out from it? And indeed it is possible. We!|ve done it. A lot of people around the world are doing it. And our dream is to take that forward as a realistic alternative technology to the main technology in the field at the moment which you uses silicon. The black stuff on glass, that most people know about and which they are going to be subsidised by governments around the world to install. So our intention is to put this cheap plastic out into the marketplace as an alternative source of electricity to the silicon solar cell.

SHANE HUNTINGTON
I hesitate to ask this question, but I must, specifically, what is happening when the light hits the plastic? In the simplest possible terms, what is the conversion?

ANDREW HOLMES
Well, I!|m going to take a step back again because we can learn a lot from nature. Of course, nature in many things, sets the example for the scientific world and of course, nature converts light into chemical energy and sometimes into electrical energy by a process which first involves absorption of the sunlight or daylight or whatever and this excites the material that is absorbing the light and normally for most organic materials, they want to relax by giving the light back out. So the challenge is to find a way of getting that excited state to give you charge seperation and for the positive charges, to say, to go to the left, and the negative charges to go to the right, then by hooking it up to a circuit, to create an electrical current.

SHANE HUNTINGTON
Just like a battery.

ANDREW HOLMES
To behave like a battery. The problem is of course that most organic molecules don!|t like separating the charge. They just like to stay with the charges together and give out the energy as heat or as light. Now, nature has a very sophisticated array of molecules which force the charges to separate. So what we have to do in plastic solar cells is exactly the same thing. We have to engineer two kinds of plastics in intimate contact with one another, the interfaces. So that at the point where the light is absorbed and the excitation takes place, the plus charges want to go into one of the bits of plastic, that like to carry plus charges, and the minus into the one that carries the minus. And that is not simple. That is the real challenge to get that to work efficiently. I should just say that silicon does this very well because one can put what we call !¢FDdopers!| into the silicon to make junctions where that happens very easily once there is an excitation.

SHANE HUNTINGTON
And I guess we have a huge amount of background knowledge on silicon, from the computer industry and others, where that exact process is crucial to operation.

ANDREW HOLMES
Well, just as in the light emitting plastic, the inorganic LED that everybody knows about, that lights up the world now, including traffic lights, people had probably 30-40 years of experience with that material, which translates very nicely into some of the basic properties in light emitting plastics as well. Similarly in silicon some of the basic breakdown pathways and problems will have the same common challenge in plastics. But there will be many more in plastics. Just think of your plastic gutters. I don!|t think there are plastic gutters in most Australian buildings because they don!|t last long enough in sunlight. That!|s a little challenge. We are trying to harness that sunlight and have plastic that survives it.

SHANE HUNTINGTON
People have heard a lot about silicon based solar power systems, in terms of a comparison between plastic based solar generation and silicon, cost?

ANDREW HOLMES
I can!|t answer that. We don!|t know yet. We haven!|t got it in the market place. Let me answer it another way. Silicon is the technology in the marketplace. And a technology in the marketplace is very hard to displace. So, we have a long way to go. That doesn!|t mean we shouldn!|t be doing it because the potential for reducing the cost is enormous. Current cost of silicon, is reckoned to be 50 cents per kilowatt hour generated. But when it is built into the rooftop, it is about $US10, a kilowatt hour. Compare that with electricity, which is not properly priced at the moment !V especially if we don!|t charge for carbon emissions, that is 5 cents a kilowatt hour.

SHANE HUNTINGTON
But how efficient are these plastic materials compared to silicon and I guess, if they are cheap enough to produce in large quantities, I guess the efficiencies goes down a bit.

ANDREW HOLMES
Same for all technologies, of course. And that is why the existing silicon technology might be the one that ends up in the market place on a huge scale as well. If the price can be reduced by bulk manufacture. Let!|s not pretend the plastic solar cells are a technology in the marketplace. They!|re not. So, we are talking about potential. At the moment, amorphous silicon, which is the non-crystalline sort on glass, is being sold in Germany, with an energy conversion of 7% and it is being sold very well with subsidies from the German government. As around most of the world. The world!|s best efforts in plastic, ours is part of that effort, for one kind of plastic where you just mix the two plastics up together. We call that the bulk polymer-hetra-junction cell, is about 5% efficiency. There is another version which is about 11%, but neither of these has been applied in anything much larger than a postage stamp area at the moment.

SHANE HUNTINGTON
You mentioned before, concerns with regards to how long they would last.

ANDREW HOLMES
Having seen when real R and D techniques are applied to technology and the light emitting plastics and taking it to what we call clean room fabrication facilities. Which means, no dust, no ingressive air and oxygen and water when you!|re making them. And then encapsulating them to prevent oxygen and water getting in. I!|m very confident that the same application of rigourous manufacturing will get around the problem of stability. The problem is not so much the sunlight, but what the sunlight can do in the presence of oxygen. And possibly with water. So, keeping those out is as much a challenge as making the cells. And it is not sunlight on its own that will do the damage.

SHANE HUNTINGTON
You!|re listening to Melbourne University Up Close. I!|m Dr Shane Huntington and today we are speaking with Prof Andrew Holmes about solar power. Plastics to me open up a whole new realm of where we could put these things, obviously solar panels, based on silicon are very restrictive in terms of where they are located, with plastics though, presumably you could spray paint a house. Is that the sort of thing you are thinking of?

ANDREW HOLMES
Yes. I think we would imagine that the ultimate opportunity would be to coat a rooftop with this material and of course. The interesting thing is in Japan, where they are really serious about renewable energy because they have no natural energy resources. The average area of a house in Japan is too small to provide sufficient coverage for a silicon solar cell to give them sufficient energy and the weight on glass is too heavy for the more flimsy houses to bear. So, plastic is light, it can be cheap if we get this technology right. And it can be made to follow any shape. And it is flexible. So, then we are not nearly as constrained and one could imagine having early applications on walls facing in the right direction where you have diffuse sunlight. So I think the idea is to start with something like a relatively inefficient and cheap technology and build on it and learn from that and improve it as we go along. This is at least 20 years away.

SHANE HUNTINGTON
I guess we call them organic photovoltaics, plastic solar panels, what are the key problems you are working on solving in your laboratory?

ANDREW HOLMES
Well, we have very fortunately, been able to persuade the Victorian State Government in Australia to support a collaboration between the major universities in the state and the Australian government research organisation, CSIRO to work together on developing a prototype plastic solar cell. And we are working on the two main branches of this technology. The one where you just mix polymers up to put it simply. And the other where you use a dye called a rhuethemian dye and you use titania, which is the white stuff that makes paint white, which is very good at absorbing electrons. That is called the dye sensitised solar cells. We are working on both of those technologies together with people who know how to print on plastic. People who are listening to this, may not know but Australia has a brilliant technology in plastic bank notes and to make that work it has had to develop the understanding of how to print on plastic. So, we can combine that know-how with the physics and the material science, to work towards a fully flexible plastic solar cell. And, we are very excited about that opportunity.

SHANE HUNTINGTON
Prof. Andrew Holmes, from the Bio21 Institute, I think its just amazing the pathway you have come along to get to solar power. Thank you very much for being our guest today on Up Close.

ANDREW HOLMES
Thank you. It has been a pleasure.

SHANE HUNTINGTON
Melbourne University Up Close is brought to you by the Marketing and Communications Division in association with Asia Institute of the University of Melbourne, Australia. Relevant links, a full transcript and more information on this episode can be found on our website, at upclose.unimelb.edu.au
We also invite you to leave your comments or feedback on this or any episode of UpClose. Simply click in the add new comment link at the bottom of the episode page. This program was produced by Kelvin Param, Eric van Bemmel. Audio recording is by Dean Collett and the theme music is performed by Sergio Ercole. Melbourne University Up Close is created by Eric van Bemmel and Kelvin Param. I!|m Dr. Shane Huntington, until next time thanks for joining us. Goodbye.

VOICEOVER
You!|ve been listening to Melbourne University Up Close, a fortnightly podcast of research, personalities and cultural offerings of the University of Melbourne, Australia. Up Close is available on the web at upclose.unimelb.edu.au, that!|s upclose.u-n-i-m-e-l-b.edu.au. Copyright 2007 University of Melbourne.


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