Washington, Oct 24 : Scientists have developed the first silicon solar cell to achieve the groundbreaking milestone of 25 per cent efficiency.
The solar cell has been developed by scientists at UNSW's (University of New South Wales) ARC Photovoltaic Centre of Excellence, in Australia.
The UNSW ARC Photovoltaic Centre of Excellence already held the world record of 24.7 per cent for silicon solar cell efficiency.
Now, a revision of the international standard by which solar cells are measured, has delivered the significant 25 per cent record to the team led by Professors Martin Green and Stuart Wenham and widened their lead on the rest of the world.
According to Professor Green, the jump in performance leading to the milestone resulted from new knowledge about the composition of sunlight.
"Since the weights of the colours in sunlight change during the day, solar cells are measured under a standard colour spectrum defined under typical operational meteorological conditions," he said.
"Improvements in understanding atmospheric effects upon the colour content of sunlight led to a revision of the standard spectrum in April. The new spectrum has a higher energy content both down the blue end of the spectrum and at the opposite red end with, dare I say it, relatively less green," he added.
UNSW's silicon cell is now six per cent more efficient than the next-best technology, according to Professor Green.
The new record also inches the UNSW team closer to the 29 per cent theoretical maximum efficiency possible for first-generation silicon photovoltaic cells.
"Blue light is absorbed strongly, very close to the cell surface where we go to great pains to make sure it is not wasted. Just the opposite, the red light is only weakly absorbed and we have to use special design features to trap it into the cell," said Dr Anita Ho-Baillie, who heads the Centre's high efficiency cell research effort.
"These light-trapping features make our cells act as if they were much thicker than they are. This already has had an important spin-off in allowing us to work with CSG Solar to develop commercial 'thin-film' silicon-on-glass solar cells that are over 100 times thinner than conventional silicon cells," said Professor Green.
According to ARC Centre Director, Professor Stuart Wenham, the focus of the Centre is now improving mainstream production.
"Our main efforts now are focussed on getting these efficiency improvements into commercial production," he said.
"Production compatible versions of our high efficiency technology are being introduced into production as we speak," he added.