Six-junction III–V solar cell with 47.1% efficiency

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Researchers from the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a six-junction III–V solar cell with a 47.1% conversion efficiency rate under 143 suns concentration.

They said that they have achieved an efficiency rate of 39.2% under one-sun illumination. The cell is based on six different photoactive layers fabricated with alloys of III–V semiconductors, which can each 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,” the scientists said.

The cell could be used in concentrator photovoltaics and has the potential to reach a 50% efficiency rate, they added. However, resistive barriers inside the cell impede the flow of current, which is the main obstacle to achieving the 50% target, they acknowledged in Six-junction III-V solar cells with 47.1% conversion efficiency under 143 suns concentration, which was published in Nature Energy this week.

In June, other NREL researchers – in partnership with scientists from the Korea Advanced Institute of Science and Technology – demonstrated a way to produce gallium arsenide (GaAs) solar cells with a reusable germanium substrate. NREL has also worked with Chicago-based Microlink Devices in the past to produce a three-junction cell with a record-setting 37.75% conversion efficiency rate.

The cost of producing solar cells based on compounds of III-V element materials – named according to the groups of the periodic table they belong to – has thus far limited such technologies to niche applications, including drones and satellites, where low weight and high efficiency are more pressing concerns than cost.