Energy from the sun, printed on plastic

Volume 11 Number 2 February 9 - March 8 2015

Dr David Jones with printable solar cells. Photo: Peter Casamento
Dr David Jones with printable solar cells. Photo: Peter Casamento

 

Andi Horvath reports on an innovation in solar technology – solar cells that are virtually indestructible, flexible, and now, printable.

Imagine for a moment if you could cross solar cells with plastic drink bottles, printer ink and a dash of LCD display technology. You would get plastic organic solar cells that are flexible, printable and provide a reasonable source of electricity. They exist and they are currently being tested at the University of Melbourne’s Bio 21 laboratories and CSIRO.  

The uptake of the current generation of organic solar cells has lagged behind more widespread silicon-based models, due to their comparative lack of performance even with a simplified construction via large printers. But that’s about to change as Dr David Jones and his team from the University’s School of Chemistry Bio 21 lab recently improved the performance of organic solar cells from around 8 per cent efficiency to 9.3 per cent, which is finally approaching the international benchmark of 10 per cent.

Dr Jones says most people are familiar with the silicon-based solar technology on urban roof tops but there is a need for other types of solar cell materials that can be printed, moulded into shapes, are durable, smash resistant and even wearable. 

“Imagine how useful durable organic solar cells on the back of a mobile phone would be,” he says. “It would provide a burst of energy to support users through a low battery situation.”

Dr Jones is renowned for encouraging visitors to the University’s annual Open Day to test the durability of the organic solar cells by swinging a mallet at samples of the cells and then testing them to see if they still work. They do. He reminds them not to try that with silicon solar cells as it won’t end well.

So how does an organic solar cell actually work and how do you get a flow of electricity? Do you remember the old potato clock or lemon battery from primary school science? Essentially the paper clip and copper wire used in those set up a separation of positive and negative charges that creates a flow of electrons, which is a flow energy we know as electricity. Organic solar cells are similar to this in concept except organic chemicals like liquid crystals can set up the positive and negative charges. The international race has been on to find the best combination of printable organic chemicals. 

Dr Jones and his group have discovered the highly sought-after ‘nematic liquid crystals’ that have improved the positive charge transport and this can now lead to vastly improved organic solar cell performance.

“It had been theorised that a certain group of nematic liquid crystals would provide excellent electronic properties,” he says, “as well as being printable. We’ve shown for the first time these are indeed high performing materials.

“These nematic liquid crystal solar cells will also be easier to manufacture. It’s a step forward for the wider commercialisation of printed organic solar cells. This research could also have an impact in development of new materials with improved performance such as LCD screens.

“We’ve seen recently at the annual Consumer Electronics Show (CES) in Las Vegas that printable electronics have an exciting future, as parts of phones and even cars. This discovery could help improve the performance of solar cells, and lead to even more innovation in printed organic electronics in the coming years. Eventually consumers can look forward to more competitive pricing in the solar energy sector,” Dr Jones says.

The research was conducted with international researchers in Singapore and Germany, and received funding from the Victorian Organic Solar Cell Consortium, and the Australian Centre for Advanced Photovoltaics.”

 

www.chemistry.unimelb.edu.au