Consortium to undertake research into OLEDs

21st February 2013

A thin film of plastic that conducts electricity and produces solar power could be the basis for a revolution in the way homes are lit and clothes are designed.

An international research project has begun that could help bring to mass-market organic light emitting devices (OLEDs), which could have far-reaching technological implications and cut the cost of lighting by billion of Euros each year.

Because the devices are thin and flexible, lighting and electronic display screens could, for the first time, be created on almost any material - so that clothes and packaging can display electronic information, for example.

The devices' uses could vary from lighting that is many times more efficient than current bulbs, to clothes whose colour can be changed at will, and beer cans that display the latest football results.

At present, the devices are used as displays in some mobile phones and MP3 players, but they are not reliable enough for larger screens such as in televisions and computers, as they stop working after a few months.

But now an international consortium of researchers, led by the University of Bath, UK, has begun an EUR1,250,000 (£850,000), three-year project to put the science behind the devices on a firmer basis, so helping to make them efficient enough to be worth producing for the mass market. The consortium, called Modecom, consists of 13 groups from nine universities and two companies. Three groups are from the UK, six from the USA, and one each from Belgium, Italy, Denmark and China. The European Union is funding the European and Chinese partners.

The devices exploit a discovery made around 15 years ago that some polymers have the unusual property of either turning electricity into light, or light into electricity, depending on their construction. Because these polymers are thin and flexible, they could be used in a multiplicity of ways:

* As a window that is transparent during the day but, at night, the entire window area is switched to emit light in a more efficient way than conventional or even energy-saving bulbs, promising huge savings.

* In garments that could change colour at the press of a button

* In clothing that displays strips of the polymer that are solar powered, allowing electronic messages to be displayed - which can also be updated. This could be useful for the emergency services, such as police or ambulance crew, for example.

* In packaging, to display electronic messages such as health warnings and recipes, or they could simply emit light.

* As a source of solar power to top up batteries in mobile telephones.

* As lightweight, solar power sources that could be rolled up and stored, and which would also be useful for people requiring electricity in remote locations, such as field researchers, mountaineers, sailors and military personnel.

The consortium is co-ordinated by Dr Alison Walker, of the University of Bath's Department of Physics, who says: This is a long-term projectand the contributions of many scientists are needed for its success. The experimentalists make measurements to test the efficiency of the devicesbut it is hard to get a clear picture of what is going on at present. This project is about making that picture clearer using computer models to develop the theory.

“Success in achieving the goals of cheapefficient and long-lasting devices is essentialas we must do everything we can to reduce our energy costs."

Electrons and holes injected into the polymer film form bound states called excitons that break down under electrical currentemitting light as they do so. Dr Walker's part of the consortium's research uses a mathematical techniquecalled Monte Carlo analysisin which computer-generated random numbers are used to plot the paths of electronsholes and excitons as they move across the film. The results from this can be used to calculate how the chemical structure and impurities affect the device's performance. Chemists can use this data to design more efficient materials.

The Modecom consortium will work on the molecular level and also look at the workings of the device as a whole. This research will also aid the understanding of the polymer materials used in plastic electronics in applications such as electronic paper and intelligent labels on groceries.

University of Bath


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