Printing solar power like money

Glen Paul: G’day, and welcome to CSIROpod. I’m Glen Paul. Solar power has been around for a while, and it’s likely you’ve used it in some capacity, from solar cells on rooftops, to gadgets such as solar powered calculators. The majority of these commercially available solar cells are made from a refined highly purified silicon crystal, which is costly and complex to produce.

Enter CSIRO and organic photovoltaics, flexible, paper thin, cost effective, printable plastic solar cells. And now with a new solar cell printer installed at CSIRO Scientists can produce these solar cells ten times the size of what was previously possible. Funded by the Victorian Organic Solar Cell Consortium, the printer is Australia’s largest, and will allow researchers to print organic photovoltaic cells the size of an A3 sheet of paper.

To find out what that means for the future of solar power, I’m joined by CSIRO’s Dr Scott Watkins. Scott, firstly you better explain the concept of a printable solar cell versus what’s powering that calculator.

Dr Watkins: Well the solar cells that we traditionally use in the calculators, on our roofs, as you say are made from silicon, but we’re using organic molecules in the form of polymers that are most closely related to things that you might see in cling wrap or polystyrene. These organic molecules absorb the sunlight, generate the charges, and produce electricity. But when we use them in these devices they’re very thin, and that’s what makes them printable and flexible.

Glen Paul: And does that mean then that the printer itself is particularly high tech, or is it based more along the lines of a traditional printer?

Dr Watkins: We’re developing the technologies to work with existing printing processes, so the printers that we’ve got are the same sort of printers that you would use for paper, or even things like t-shirts, and we’re developing our processes to be able to use these existing printing technologies so that the barrier to entry for manufacturing these new printed solar cells is as low as possible.

Glen Paul: So how did you tackle the problem then of reworking a printer into doing what you wanted it to do in printing these solar cells?

Dr Watkins: It’s actually a really nice story. We’ve been working with a local printing company here in Victoria who have a lot of experience in printing advertising hoardings around building sites, and they were able to help us find a printing manufacturer who was able to make some small customisations to an existing paper based printer, and then the local Victorian company was able to help us install and set up the printer, and transfer some of their decades of printing expertise on fabrics to printing solar cells.

Glen Paul: So you literally just print them off, take them out, and stick them where you need power. And where do you see them being used?

Dr Watkins: In the short term there’s applications for these in indoor displays, or powering small consumer devices, or even powering advertising type applications; in the medium term incorporating them into building integrated situations, such as windows in office buildings; and finally rolling them out onto rooftops and powering large areas is what we’re aiming to do eventually.

Glen Paul: And when you say incorporate do you mean you still have to print them off and stick them on, or is there a way of actually incorporating them into the production process of a building material?

Dr Watkins: At the moment we’re actively working on printing them on plastics, so you would stick them on, but we’re also looking at directly printing onto materials like steel roofing, and one of our key partners in this is BlueScope Steel, so actually building them up from the building material, on the roofing material in particular, is a key aim of what we’re doing.

Glen Paul: And how do you feed the power from the solar cell to the device requiring the power? Are there wires that come out of it? How does it work?

Dr Watkins: We do have wires, but those wires can be printed as well, and so they can conform to the structure that the solar cells are built into, and they come out and are fed into an inverter, or directly to the device, as for any existing solar cell.

Glen Paul: And how will these organic photovoltaic solar cells compete against the traditional silicon crystal?

Dr Watkins: Well, it’s a really big market, and we’re not necessarily looking to compete, rather to complement, and so organic solar cells do things that traditional silicon solar cells don’t do. So for example they perform a little bit better under low light conditions, they can offer different colours, and different form factors, and they can also absorb different parts of the sunlight than silicon solar cells do, so you can even make them work together.

So there’s, as I said, there’s a big market there, and we really see them as complementing, or moving into areas that traditional solar cells can’t currently work in.

Glen Paul: And what about power output, will they have an impact on the electricity grid?

Dr Watkins: Certainly in the short term we’re focused on small scale applications where you currently need portable power. But in the long term, when we have the vision and belief, that we can develop these cells to actually contribute significant amounts of power to our grid and to our society.

Glen Paul: And obviously powering up batteries is going to be a major factor for this technology?

Dr Watkins: That’s exactly how we think they will work in many, many applications. So there’s all sorts of developments happening in battery technologies as well, very thin rechargeable batteries, and they could be even printed onto the back of the solar cells and then incorporated into a device.

Glen Paul: And the plastic itself used in the construction of the solar cells, is it a fairly inexpensive polymer?

Dr Watkins: At the moment the plastic that we’re mainly using is PET, and that’s the same plastic that makes your soft drink bottles. Coated onto to the top of that is a conducting electrode, and at the moment that’s indium tin oxide, and that’s the same electrode that’s used in your displays for your computer monitors or phones. There’s certainly opportunities to develop alternative electrode materials that goes onto the PET, and that is one area where the field as a whole is looking to reduce costs. But there are solutions out there at the moment that are cost effective.

Glen Paul: And what’s the life expectancy of one of these solar cells that’s outdoors in the harsher environment?

Dr Watkins: We’ve got solar cells outdoors that we’re currently testing that are showing lifetimes out beyond six months. We anticipate in the next few years that we’ll be able to improve that to a couple of years. We need the encapsulating material to keep the oxygen and water out to stop the electrodes degrading. It’s actually not the polymers themselves that are degrading, and they’re certainly stable to the UV light that they are exposed to.

So we’re constantly trying to improve that. And other substrates such as steel and glass provide even better protection, and so the lifetimes on them would be even longer.

Glen Paul: OK. Well look, it’s an amazing story, and you’ve got this wonderful printing technology, and the chance to scale up. Are you looking for more commercial collaborators?

Dr Watkins: Certainly we’re looking to expand this into as many different applications as we can. We have a couple of key collaborators at the moment, including BlueScope Steel, and Innovia Security, and our research partners at Monash University and the University of Melbourne, all of us are working together to develop a couple of specific applications.

But we are looking to work with other manufactures here in Australia, we have this printing facility now, and it is there. We have the capacity to do small scale pilot production runs in specific applications. So the message is, yes, the facility is up and running, and open for business.

Glen Paul: And does that include internationally?

Dr Watkins: Certainly. This is a very international field, and we look all around the world for our expertise and partners.

Glen Paul: OK. So if there is somebody listening out there in the world who wants to get involved, they can email you directly?

Dr Watkins: Correct. Scott.Watkins@csiro.au.

Glen Paul: And no doubt they can find plenty of information on the CSIRO website?

Dr Watkins: Yeah. If you look at csiro.au/flexibileelectronics, there’s a lot of information and some videos there about what we’re doing.

Glen Paul: Portable stick on power certainly sounds like the way of the future. Thank you very much for chatting with us about it today, Scott.

Dr Watkins: Thanks, Glen.

Glen Paul: Doctor Scott Watkins. And to find out more about the research, or to follow us on other social media, just visit www.csiro.au.