“At present, the world record triple-junction solar cell efficiency is 44 percent under concentration and it is generally accepted that a major technology breakthrough will be required for the efficiency of these cells to increase much further,” so states Dr. Robert Walters, a Navy Research Laboratory (NRL) Research Physicist.
Now Dr. Walters and a team of scientists from the Electronics Technology and Science Division at the NRL, in collaboration with other institues such as Imperial College London, have developed a new triple junction solar cell which has the potential to work at a conversion efficiency of 50 percent.
“This research has produced a novel, realistically achievable, lattice-matched, multi-junction solar cell design with the potential to break the 50 percent power conversion efficiency mark under concentrated illumination,” he said.
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As the name suggests multi-junction solar cells are made of several junctions which can be tuned to different wavelength bands of the solar spectrum to increase the energy absorbed and the overall efficiency of the cell. Eg. a triple junction cell can absorb the energy from three different wavelength bands.
In theory a cell with infinite junctions could have a conversion efficiency of around 87 percent. The barrier to developing cells with many junctions is the challenge of developing a semiconductor material which can attain a wide range of bandwidths and maintain a high crystalline quality.
The group of researchers have recently been awarded a grant from the US Department of Energy under the ARPA-E scheme in order to undertake in a three year materials and device development program to realize this new technology.
By. Charles Kennedy of Oilprice.com