Solar cell converts sunlight with metamorphic junctions

Solar cell converts sunlight with metamorphic junctions

An inverted metamorphic multijunction (IMM) solar cell was recently developed at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). Originally designed by Mark Wanless and further modified by John Geisz and his team, the cell has a solar conversion rate of 40.8% the highest confirmed efficiency of any similar device to date.

NREL’s John Geisz and Mark Wanless have developed a solar cell that offers the highest confirmed efficiency of any similar device to date.

Unlike conventional designs, the new cell uses compositions of gallium indium phosphide and gallium indium arsenide that separates the solar spectrum into three equal parts to be absorbed by each of the cell’s three junctions. The solar cells are grown on a gallium arsenide wafer, then turned upside down and the wafer is removed. This method allows for much thinner and lighter devices to be created. It was Geisz’s team that improved the junction energies by making the middle and bottom junctions metamorphic. These metamorphic junctions are lattice mismatched, meaning they do not follow the pattern of even atomic spacing, which allows for greater potential conversion of sunlight.

The efficiency of the IMM was measured under concentrated light of 326 suns, which is over three hundred times the amount that typically hits Earth on a sunny day, making it a prospect for applications in the space satellite market or terrestrial concentrated photovoltaic arrays. For more information, contact NREL Public Relations at 303-275-4090 or http://www.nrel.gov.

Christina D’Airo