25 May 2012
Researchers set new record for graphene solar cell efficiency
University of Florida researchers have set a new efficiency record for graphene solar cells.
By chemically treating, or doping, the graphene with trifluoromethanesulfonyl-amide (TFSA), the team was able to achieve a power conversion efficiency of 8.6%, a development which could provide hope for cheaper, durable graphene solar cells in the future.
"The dopant makes the graphene film more conductive and increases the electric field potential inside the cell," said Xiaochang Miao, a graduate student in the physics department at the university. "That makes it more efficient at converting sunlight into electricity. And unlike other dopants that have been tried in the past, TFSA is stable - its effects are long lasting.
According to Miao, the solar cell consists of a 5mm2 window of silicon coated with a monolayer of graphene, which is framed in gold. The graphene and silicon come together to form what is called a Schottky junction, which Miao describes as a 'one way street' for electrons. When illuminated with light, this acts as the power conversion metal on top of a semiconductor.
"Graphene, unlike conventional metals, is transparent and flexible, so it has great potential to be an important component in the kind of solar cells we hope to see incorporated into building exteriors and other materials in the future," said Arthur Hebard, distinguished professor of physics at the University of Florida. "Showing that its power converting capabilities can be enhanced by such a simple, inexpensive treatment bodes well for its future."
The researchers said that if graphene solar cells reach 10% power conversion efficiency, they could be a contender in the market place, but only if production costs are kept low enough. They are now looking to build the solar cells on polymer sheets instead of silicon, in a bid to drive down cost.