DESLEY BLANCH : If you can picture printable nanotech solar cells which can be painted or printed directly onto a surface then you immediately imagine how the breakthrough will do away with the need for bulky solar panels to be attached to buildings as happens now.
Plus, this initiative has the potential to dramatically bring down the cost of solar energy.
With help from CSIRO (Australia's premier science research organisation), PhD student Brandon MacDonald has worked out how to use nanocrystals to make solar cells.
Brandon is Canadian-born and is doing his PhD at the University of Melbourne.
Their patented technology is based on inks containing tiny, semiconducting nanocrystals as he explains.
BRANDON MACDONALD : The inks contain very, very tiny crystals called nanoparticles or nanocrystals. These are on the scale of a millionth of a millimetre in size, so extremely tiny and in terms of the patent what we've actually come up with is a new method of using these as a way of making solar cells.
DESLEY BLANCH : So what kinds of surfaces can be printed onto?
BRANDON MACDONALD : So we can print these onto a variety of surfaces, so as with traditional solar cells we can make them onto glass, but because we use lower processing temperatures and techniques compatible with printing, we can also deposit them on surfaces such as certain plastics or thin sheets of metal. And so what this does is now we can make cells which are much more lightweight and flexible and this can increase the range of applications they have.
DESLEY BLANCH : So when you're applying it to a surface, do you put it on in layers, is that how it works?
BRANDON MACDONALD : Yes, so that's the innovation we've made over previous attempts at using nanocrystals-based solar cells.
So what we found is that if you deposit simply a single layer and then let that dry, much like with paint you can get cracks and defects which form and that negatively affects the performance of the solar cell. So what we've developed is a method where we apply a layer and then essentially dry it and give it a bit of heating and then we apply subsequent layers which are able to fill in the cracks and defects which form and so overall, we get a much more uniform layer of material and much better solar cell performance.
DESLEY BLANCH : As you said these nano solar cells are thin, they're flexible and they use just a one-hundredth of the materials of conventional solar cells, which makes me wonder how they still work. So can you explain how they work?
BRANDON MACDONALD : They work in a very similar fashion to conventional solar cells. The big difference is the material which we use.
So conventional solar cells are based on silicon and silicon is not a very strong light absorber, so in order to produce energy from the sun, you need to first absorb a large portion of the sunlight and to do that with silicon you need a lot of material, whereas the nanoparticles we use are very strong light absorbers and so what you're able to do is make cells which are very, very thin, but still absorb a large amount of the light and then can turn this into electricity.
DESLEY BLANCH : Now is this why you say your technology can dramatically decrease the cost of solar energy?
BRANDON MACDONALD : Yes, that's one of the reasons that we think that this could drive down the cost of solar energy. As well we use much lower processing temperatures than a conventional silicon cell, so we process our cells at approximately 300 degrees whereas a conventional cell can be upwards of 1,000 degrees Celsius. We also have much shorter processing times and if we're able to develop this to a stage where we can print this on a continuous basis, it will make the production of the cells much, much faster as well.
DESLEY BLANCH : Okay, so you need to get the combination right though with ink and surface to make the cells work efficiently; a bit more on that.
BRANDON MACDONALD : Yes, so to make a solar cell you need your light absorbing material, which can also transport an electronic charge and much like a battery, you also need two terminals so a positive and a negative terminal and so you need to as you said choose the right materials and make sure it all sort of works together as a unit to make an efficient solar cell.
DESLEY BLANCH : I've got this image of a tiny, tiny, tiny nano-cell with plus and minus battery terminals on it and it doesn't quite gel. Can you tell us more about how those battery connections work?
BRANDON MACDONALD : Okay, sure. So the way a solar cell works is when you can imagine light as sort of particles of light, so when a particle of light hits the solar cell, it gets absorbed and transfers its energy and what that does is it creates both a positive and negative charge within the solar cell and what we then aim to do is to separate those two charges so we'll have the negative charge go to the negative terminal, the positive one move to the positive terminal and then we can have the charges move through a wire and that's how they provide electricity and power.
DESLEY BLANCH : What are nanocrystals or these quantum dots as they're also known?
BRANDON MACDONALD : Nanocrystals; the 'nano' part refers to the length scale that we're working on, so these things are nanometres in size, which is billionth of a metre.
There are essentially two different approaches to how you can make these nanocrystals or quantum dots. You can use what's called a top-down approach in which you take a larger material and break it into very, very small pieces, but what we use is what's known as a bottom-up approach where we start with individual atoms or molecules and use synthetic chemistry to assemble them into the nanocrystals of the size or the shape that we want.
DESLEY BLANCH : You say the technology is not limited to solar cells, so what else can it be used to make?
BRANDON MACDONALD : Nanocrystals can be used in all sorts of different electronics, so my project is focused on solar cells, but there are also people working on using them for lighting applications, so for making light emitting diodes, LEDs which essentially operate the same as a solar cell, but in reverse. So you're taking charges, putting electricity in and getting light out. You can also use them to create transistors which are what makes computers function and there's work on trying to design lasers based on nanocrystals as well.
DESLEY BLANCH : So how much cheaper would you hope the new technology would be from solar cells currently on the market?
BRANDON MACDONALD : At that point it's hard to say exactly how much cheaper it would be. This is still very much in the research phase. But what we're hoping is that we can drive down the cost of solar energy perhaps two or three times and get to a level where it's on par with energy produced from coal and other conventional energy sources.
DESLEY BLANCH : So when might the new technology reach the market, still guessing ?
BRANDON MACDONALD : Yeah, it's always hard to predict with these things when they'll reach the market, but we think if we can continue to make some research breakthroughs and get some funding, this is something that could be on the market in the next five to ten years.
DESLEY BLANCH : So what's it feel like right now as you've reached this point of publishing the research?
BRANDON MACDONALD : Oh, it's exciting. This is something that myself and a few other researchers have been working on for about three years now and to reach the point we're able to sort of take this and publish it and take it out into the public arena is a very exciting experience.
DESLEY BLANCH : PhD student Brandon MacDonald whose research with CSIRO is making paint-on solar panels possible.
Next week, Innovations Sounds of Summer looks at Lifestyle: how to detect liars, a new model for understanding music and the perils of a sedentary lifestyle.
Until then, I'm Desley Blanch saying bye for now.
More information:
Brandon MacDonald, PhD Student
CSIRO Materials Science and Engineering Clayton, VIC 3168
