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University of Exeter researchers develop graphene photoelectric device

Sara Ver-Bruggen - 24 Apr 2013

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A flexible and transparent photosensitive device based on graphene and the GraphExeter material has been developed by a research team at the University of Exeter.

GraphExeter is a room-temperature transparent conductive material based on grapheneThe photoelectric device converts light into electrical signals by exploiting the unique properties of graphene and the more recently discovered GraphExeter material - a room temperature transparent conductor.

The photoelectric device is just a few atoms thick, is ultra-lightweight and flexible, opening up the possibilities of integration into a range of substrates and surfaces.

The discovery could pave the way for an energy harvesting device that is extremely thin, able to harvest light from across the whole visible light spectrum, and completely transparent, unlike current third generation solar cell technologies such as organic photovoltaics (OPV), which are semi-transparent.

But in order to develop an energy harvesting device based on graphene further electrical properties of the materials need to be engineered. 'We will need both p-type (hole doped) and n-type (electron doped) graphene. The recently discovered graphexeter is a p-type graphene, but we are still missing an equivalent form of n-type graphene,' explains Dr Saverio Russo, who along with Dr Monica Craciun, led the University of Exeter's team of researchers as part of efforts to develop GraphExeter.

Dual functionality

Russo confirms that in future the discovery could form the basis of a material that combines two properties to make a transparent conductor (ITO alternative) that also has energy harvesting properties, for a display application for instance, and this is a goal that the researchers are working towards.

The photosensitive part of the device is the interface between graphene and GraphExeter. Owing to the difference in fundamental physical parameters between these carbon materials, when a photon impinges onto this interface the charge carriers are excited and a photo-current is generated.

The graphene is synthesised by mechanical exfoliation of the bulk material graphite. GraphExeter is a functionalized form of graphene, based on a stack of a few graphene layers with molecules of ferric chloride introduced between the layers of the stack, to enhance graphene's conductivity without reducing its transparency. The fabrication of the actual photosensitive interface uses standard micro-fabrication techniques so is compatible with standard semiconductor processes.

A number of industrial partners are currently involved in the commercialization of the GraphExeter material. The range of applications targeted range from mainstream displays technology to electronics for very harsh environments such as nuclear power reactors.

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