NREL breaks two world records for efficiency with new solar cells
Scientists at the national renewable energy laboratory (NREL) have created a six-junction solar cell with an efficiency of nearly 50%, marking the world record for the highest solar conversion efficiency at 47.1%. a variation of the same cell also set the efficiency record under one-sun illumination at 39.2%.
‘This device really demonstrates the extraordinary potential of multijunction solar cells,’ comments john geisz, principal scientist in the high-efficiency crystalline photovoltaic group at NREL and lead author of a new paper on the record-setting cell.
The device was constructed by NREL researchers with III-V materials which have a wide range of light absorption properties. each of the cell’s six junctions — the photoactive layers — has been specially designed to capture light from a specific part of the solar spectrum. the device contains about 140 total layers of various III-V materials to support the performance of these junctions, and yet is three times narrower than a human hair. due to their highly efficient nature and the cost associated with making them, III-V solar cells are most often used to power satellites.
‘One way to reduce cost is to reduce the required area,’ geisz continues. ‘and you can do that by using a mirror to capture the light and focus the light down to a point. then you can get away with a hundredth or even a thousandth of the material, compared to a flat-plate silicon cell. you can use a lot less semiconductor material by concentrating the light. an additional advantage is that the efficiency goes up as you concentrate the light.’