Device points to graphene-based ‘smart windows’

Smart windows that act as computer displays and harvest their own electricity may be a step closer following research to build such devices using graphene.

Researchers at Exeter University have found a way to use the much-lauded two-dimensional form of carbon to make a flexible and completely transparent light sensor, which could become part of a new generation of electronics.

The scientists combined graphene with an enhanced version of the material of their own creation – graphExeter – to improve the efficiency with which graphene-based photoelectric devices turn light into electrical signal but also allowing them to be made completely transparent.

‘It had been demonstrated that similar efficiency was possible with graphene-gold interfaces,’ research leader Prof Saverio Russo told The Engineer.

‘But if you wanted to have a photosensitive window then having metallic nanostructures embedded into these devices would make light scatter off the nanoparticles and you would suffer from haze.’

Electronic devices that used graphExeter rather than metals would also be lighter and cheaper to make, he added.

Graphene has been widely praised for its potential to contribute to the electronics industry because of its high strength, flexibility and light weight, and the UK and Europe have been pouring money into graphene research.

But limits in the way the material conducts electricity and the lack of cheap mass production methods have so far held back its application.

The Exeter researchers hope their breakthrough could lead to flexible components such as solar panels and keyboards that could be integrated into clothing, or contribute to the anticipated trend for electronic displays built into glasses.

The key to combining graphene and graphExeter, which is made from several sheets of graphene interspersed with layers of ferric chloride molecules, was understanding the physics behind what happens at the interface of the two materials.

Russo said the new research clarified that current was driven across the interface primarily by the voltage or electric potential induced in response to a temperature difference rather than the voltage induced in response to a built-in potential (photovoltaic effect) at the interface between the two materials.

‘This is a piece of knowledge you would need in order to develop more complicated structures. It means if you want a larger signal to make more efficient devices then you will know what you need to engineer in the materials to enhance the properties of these devices.’

The researchers now plan to build on this knowledge to create light-harvesting devices, in particular graphene-based solar power generators that could be integrated with clothing.