Clean Power

Published on May 6th, 2014 | by James Ayre


New CPV Cell Brings 50% Conversion Efficiency Closer, Says Developer Semprius

May 6th, 2014 by  

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

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.

Keep up with all the hottest solar power news here on CleanTechnica, or even subscribe to our free solar power newsletter.

Image Credit: Nature Materials

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

  • vensonata

    If one is currently buying an off grid solar pv system, you will notice that the pv panels cost approximately 10% of the whole package over the 35 year life of the panels. Inverter, batteries, battery charge controller, mounting racks, wiring and labour, will add 9 dollars per watt to the 1 dollar per watt of the panels available now. Fall in prices of panels can’t make more than a 5% difference to the final cost. That final cost though is not bad…about 21cents per kilowatt hour. It is storage and inverters which need to fall by 50% to make off grid a tempting alternative to the grid. Why go off grid? Same as deciding to own a personal car vs taking the bus or subway. Not everyone will but many might prefer the new availability of cheaper land and the fixed costs of your own energy system.

    • 99% of PV is grid connected, so the battery costs do not apply there.

      In a typical roof mounted installation I still see the panels making up 60% of total costs. Inverter is 15% and labour, racking, cabling is the remaining 25%. So there is still considerable downside potential, as I expect inverters to get cheaper too. Labour costs can be reduced as the solar installation branch gets more experienced and installs higher volumes.

      We haven’t reached the bottom yet, not even close.

  • JamesWimberley

    James pitches this right. A 0.1% gain in mass-market silicon pv is more important than a 0.5% gain at the boutique end. The Holy Grail is cheap fabrication of multi-junction cells.

    • These cells are meant for cpv panels and as such can have more potential than ’boutique’ status.

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