NREL Builts 1-Sun Solar Cell With Unparalled Efficiency

The record-setting solar cell shines red under blue luminescence

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The record-breaking efficiency of a solar cell under 1-sun global illumination was achieved by researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). This solar cell is the most efficient of all types, measured under standard 1-sun conditions.


Myles Steiner, a principal investigator and senior scientist in NREL’s High-Efficiency crystalline photovoltaics (PV) Group, stated that the new cell was more efficient and simpler. Ryan France, John Geisz and Tao Song were his NREL colleagues. Michelle Young was also involved.

The paper “Triple-junction Solar Cells with 39.5% terrestrial efficiency and 34.2% space efficiency enable by thick quantum well supralattices” outlines the details of this development. It appears in the May issue.

NREL scientists set a new record for 2020 by setting a 39.2% efficiency six-junction solar cells using III-V materials.

Many of the most recent solar cells are based on the NREL-invented inverted metamorphic multiplejunction (IMM), architecture. The Best Research-Cell Efficiency Chart now includes the newly improved triple-junction IMM solar cells. This chart shows the success of experimental cells and includes the 37.9% previous three-junction IMM record, which was established by Sharp Corporation of Japan in 2013.

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Research into “quantum well” solar cells led to an improvement in efficiency. These solar cells use many thin layers to alter the properties of solar cells. Scientists created a quantum-well solar cell that was extremely efficient and integrated it into a device with three junctions of different bandgaps. Each junction is tuned to capture and use a different portion of the sun’s spectrum.

The III-V materials are named for their position on the periodic table. They have a wide range energy bandgaps, which allow them to target different parts the solar spectrum. The top junction is made from gallium-indium phosphide, the middle of gallium arsenide with quantum wells and the bottom of lattice mismatched gallium idium arsenide. Over decades of research, each material has been optimized to its best.

France, senior scientist, and cell designer, stated that GaAs, while an excellent material, isn’t the right bandgap for a 3-junction cell. This means that there is an imbalance of photocurrents between them. We have altered the bandgap and maintained excellent material quality using quantum wells. This device can be used for other purposes.

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To increase the light absorption capacity of GaAs cells, the scientists used quantum wells in their middle layer. They were able to create optically thick quantum-well devices with minimal voltage loss. In separate publications, they also discussed how to anneal GaInP top cells during growth to increase its performance. They also discovered how to reduce threading dislocation density for lattice mismatched GaInAs. These three materials are the basis of the new cell design.

Although III-V cells have a high efficiency rating, their manufacturing process is expensive. The III-V cell has been used so far to power unmanned aerial vehicles and space satellites. Researchers at NREL are working to reduce the manufacturing costs of III-V cell and provide alternative cell designs that will make them more affordable for a wide range of new applications.

For space applications, particularly for communications satellites powered by solar cells, the new III-V cell was tested. It scored 34.2% in a beginning of life measurement. The current design of the cell can be used in low-radiation environments. However, further development of this cell structure may allow for higher-radiation applications.

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NREL is the primary U.S. Department of Energy national laboratory for energy efficiency and renewable energy research and development. The Alliance for Sustainable Energy LLC manages NREL for the Energy Department.

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