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Organic electronics research replaces costly ITO

Dan Rogers - 08 Apr 2010


US research into organic electronics has produced a replacement for indium tin oxide (ITO).

The plastic transistor tested at Princeton shows current passing through in greenThe research team at Princeton University in New Jersey, US, has developed a suitably conductive layer for plastic electronics, such as organic solar cells, that could challenge the performance of ITO.

ITO is currently used as a means of conducting electrical charge in plastic electronic devices, such as displays and photovoltaics (PVs), but its brittleness and high cost do not compliment the selling points of flexible, cheap-to-print organic electronics.


Conductivity

Associate professor of chemical engineering and lead researcher Lynn Loo says: 'While [plastic electronic materials like] PEDOT:PSS are fantastic for production, they lose conductivity by several orders of magnitude.

'What we've come up with is a way to manipulate the structure of these materials to recover conductivity, bringing it up by two orders of magnitude.'

The new process involves immersing an organic electronic substrate in a solvent, which compensates for the loss of conductivity.

And it is ready to be tested as part of a commercial process, says Loo.

'The polymer process is scalable. I can easily imagine the soaking of a solar panel in a warm acid bath for three minutes being incorporated into continuous production,' she comments.


Organic solar cells could use the material instead of less suitable ITO Replacement

While there has been a sustained effort to find replacements for ITO in recent years - with R&D groups looking at metal and carbon nanotube (CNT) alternatives - none has proven compelling in terms of matching ITO's attributes while offering easier and cheaper production.

Loo says: 'Some companies are still trying to make metal oxides, which doesn't really solve the problem. Others are working on grapheme and CNTs, but I haven't seen a convincing case for one of those. When the conductivity gets sufficiently high, they're so absorptive that you're not getting a whole lot of light through.'

However, she believes the new material is competitive.

Loo remarks: 'The material has 85% transparency, compared to ITO's 93%, and it's slightly more resistive. It's comparable though - and when you see how much of a cost saving can be made, it's tremendous.'

The Princeton researchers are now looking to develop industrial partnerships to confirm the degree of cost saving in volume manufacturing, and begin selling the material to solar cell and touchscreen display producers.

'I'm excited about replacing ITO. If we can show our material is useful, it's going to be big. How quickly that happens depends on the partnerships we form with industry,' Loo concludes.

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