Friday December 26, 2014 0 comments
GOLDEN - The National Renewable Energy Laboratory (NREL) announced the demonstration of a 45.7 percent conversion efficiency for a four-junction solar cell at 234 suns concentration.
NREL said the achievement represents one of the highest photovoltaic research cell efficiencies ever achieved across all types of solar cells.
NREL's new cell, which is designed for operation in a concentrator photovoltaic (CPV) system where it can receive more than 1,000 suns of concentrated sunlight, greatly improves earlier designs by incorporating an additional high quality absorber layer to achieve an ultra-high efficiency.
Multi-junction solar cells harvest sunlight by dividing the solar spectrum into portions that are absorbed by a material with a bandgap tuned to a specific wavelength range.
Combining materials with optimal bandgaps is critical for high efficiency, NREL said.
"The distinction of this multi-junction device is the very high quality of the lattice-mismatched subcells," said Ryan France, NREL scientist and designer of the solar cell.
"Lattice mismatched materials require the introduction of defects, called dislocations, into the device, which can drastically hinder device performance.
"NREL has learned to control and confine these dislocations to inactive regions of the device, allowing even highly mismatched material to be used in a multi-junction cell."
The project is supported by the U.S. Energy Department's SunShot Initiative, a national effort to make solar cost-competitive by the end of the decade by bringing the cost of solar down to 6 cents per kilowatt-hour.