Scientists trump US in solar cell battle

Richard Macey

Sydny Morning Herald, August 22, 2009

http://www.smh.com.au/environment/scientists-trump-us-in-solar-cell-battle-20090821-ett3.html

SYDNEY scientists have scored gold, helping create the world's most efficient technology for turning sunlight into electricity.

Just as swimmers and runners struggle to shave 10ths of a second off their times, solar cell scientists battle for years to add fractions of a per cent to the efficiency of their creations.

US researchers developed experimental technology that could turn 42.7 per cent of the sunlight received into power - a world record.

By comparison, commercial cells often used in solar modules on Australian roofs convert only about 15 per cent.

The US technology was made of five separate cells, each tuned to draw energy from different parts of the light spectrum. One, for example, was designed to collect energy from the ultraviolet light band, while another, at the other end of the spectrum, was tuned to the far infrared.

By replacing one of the US cells with a new design developed by the Photovoltaic Centre for Excellence at the University of NSW, the technology's efficiency has now been nudged to a record 43 per cent.

The Sydney cell converts 46 per cent of red and near infrared light received into electricity, ''dragging up'' the overall efficiency of the American technology just 0.3 percentage points.

While progress may seem agonisingly slow, ''years of effort went into developing the cell'', the university's photovoltaic centre research director, Martin Green, said.

Although highly experimental, and far too expensive for commercial solar panels, the cell will inevitably inspire other researchers to race to develop even better technology.

''You encourage people to try to beat what you have done,'' Professor Green said.

''It pushes the state of the art even further. There is a lot of interest in being the best.''

Professor Green estimated that by combining hundreds of advanced experimental cells, each tuned to different parts of the spectrum, an efficiency rating of up to 86 per cent was theoretically possible. But, he warned, ''it's not as easy as it sounds''.