NREL Scientists Achieve Six-Junction Solar Cell Efficiency of Over 47%

The scientists at the National Renewable Energy Laboratory (NREL) have developed a solar cell that has an efficiency exceeding 47%.

The latest offering, which is a six-junction solar cell, now holds the highest solar conversion efficiency of 47.1% under concentrated illumination. A variant of the same cell has also set the record under one sun illumination at 39.2%.

Speaking about the potential of multi-junction cells, John Geisz, principal scientist at NREL, said, “This device demonstrates the extraordinary potential of multijunction solar cellsNREL.”

To construct the device, the researchers at NREL relied on III-V materials (named according to their position in the periodic table) that have a wide range of light-absorbing properties. Each of the cell’s six junctions is designed in such a way that it captures light from a specific part of the solar spectrum. This new cell contains about 140 layers of III-V materials to support the performance of these junctions, and yet the device is three times narrower than the human hair.

The highly dynamic nature of the III-V solar cells and the cost associated with developing these cells make it an ideal component to be used in satellites.

According to Ryan France, a scientist in the III-V multijunction group at NREL, the six-junction solar cells are well suited for the use of concentrators photovoltaics.

“One way to reduce cost is to reduce the required area, 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 use a lot less semiconductor material by concentrating the light. An additional advantage is that the efficiency goes up as you concentrate the light,” he said.

France said that solar cells could very well exceed the 50% efficiency mark, but the cells cannot achieve the 100% mark because of the limits of thermodynamics.

Geisz said that the main hurdle in the path of exceeding the 50% cell efficiency barrier is to reduce the resistive barriers inside the cells, which act as an impediment and slows down the flow of the current. The team of scientists is also working toward reducing the cost of the III-V solar cells, which could pave the way for its wider adoption.

This research was funded by the Department of Energy, Solar Energy Technologies Office.

Recently, Canadian Solar, a global solar module supplier and project developer announced that its team of researchers had set a world record of 23.81% conversion efficiency using the n-type large area multicrystalline silicon solar cell.

Earlier, Researchers from the Hasselt University, Interuniversity Microelectronics Centre (imec), VITO, EnergyVille, and PERCISTAND consortium claim to have achieved a rare feat of 25% efficiency using a thin-film solar cell.