New materials produced for future organic electronics

16 Feb 2010

A new molecule has been developed by US researchers that could dramatically increase the stability of organic electronic devices.

Researchers at the University of New Hampshire (UNH) recently announced the development of nonacenes, a larger and more advanced structure of acenes, a material with potential in electronics such as organic photovoltaics (OPVs) and OLEDs.

The new molecules offer greater performance than those currently used and have been designed to counteract the instability of acenes.

Glen Miller, associate director of the Centre for High-rate Nanomanufacturing at UNH explains: 'As acenes get larger, their stability drops tremendously and they are even more prone to degradation.'

While smaller molecules such as pentacenes have been tested in devices with stabilities of around a year at best, nonacenes were previously so unstable that no molecules were actually created.

Miller adds: 'Nonacenes were not prepared before, because they would not be stable for more than a few seconds. All the theories of performance in devices were only made computationally.'

However, the research means that days or weeks of stability can now be achieved with nonacenes, meaning that the first trials of nonacene-based devices can now be done.

Miller states: 'We're collaborating with electrical engineers at Northeastern University and preparing some simple transistor devices with nonacenes. We will be doing our first tests for performance properties within the next few months.'

Stability

Acenes consist of linearly fused benzene rings, and molecules with a higher number of rings (such as five-ringed pentacenes) offer high performance for electronic devices.

However, their susceptibility to degradation from light and oxidisation poses a problem for long-life commercial devices, particularly in the solar industry. As a result, OPV companies such as Konarka have turned to alternative materials like fullerenes.

If nonacenes could match or even better the stability of fullerenes, as Miller believes they will, then organic electronic companies will be persuaded to adopt the higher-performance molecules.

Says Miller: 'There is real potential here. If we make them as robust as fullerenes, they would become quite compelling compared to existing materials.

'The stabilities we've achieved so far are still not ideal, but are going in the right direction.'

And, with ties to the industry-linked Centre for High-rate Nanomanufacturing, Miller believes that current collaborators could be testing nonacenes in OPV applications soon.

He concludes: 'We've had a few informal enquiries and we're interested in pursuing collaborations with industry. We have very good industrial relations through the centre, particularly with some PV companies, so there may be opportunities there.'