A newly created four-junction stacked CPV solar cell from the manufacturer Semprius brings the industry one step closer to the oft-stated goal of a solar cell with a 50% conversion efficiency.
The North Carolina–based developer says that its latest four-junction, four-terminal solar cell — which utilizes Sempius’ micro transfer process — can reach efficiencies as high as 43.9%. Not far off from the stated goal of 50%.
Semprius solar cell
The new cell is created through the stacking of a three-junction microcell onto a single-junction germanium microcell via high-speed micro transfer — which allows for “thousands of stacked microcells with very high yields to be simultaneously formed.”
The press release provides more:
By using four junctions, the stacked cell is able to capture light across a broader portion of the solar spectrum and therefore achieve efficiencies much higher than conventional silicon and thin-film single-junction solar cells. Initial trials yielded solar cells with measured efficiencies up to 43.9%. This process is capable of achieving solar cell efficiencies greater than 50% in the near future.
A key achievement of this project was the development of a new interfacial material that is placed between the top and bottom cell to minimize optical losses within the stack and thereby optimize overall conversion efficiency. In addition, the new stacked cell has four terminals, rather than the standard two. This reduces the spectral dependence of the solar cell and increases the solar cell’s energy yield under normal operation in the field.
“This achievement is notable because it establishes a straight-forward path to significant future increases in conversion efficiency,” stated Dan Friedman, manager of the National Renewable Energy Laboratory III-V Multijunction Photovoltaics Group. “Increasing efficiency is critical to reducing the cost of solar energy because it helps drive down not only module costs, but also many other costs, including the cost of land, labor and wiring.”
While the 50% conversion efficiency certainly sounds impressive — and the new cells no doubt do have a number of different potential applications — relatively expensive high-efficiency solar cells such as these will have a really hard time competing in the market against cheaper, lower-efficiency polycrystalline cells. That said, it’s good to see work such as this driving the technology forward.
For more information on Semprius, check out some of our previous coverage of the company’s work: New Solar Module Efficiency Record.. & These Modules Are Coming to Market; and Semprius to Produce Dot-Sized, Low Cost-High Efficiency Solar CPV Cells, Modules at NC Plant.
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Image Credit: Nature Materials
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