Pushing the envelope on CPV triple-junction cell performance is VC-funded Solar Junction, which just hit an NREL-verified 44 percent cell efficiency (at 947 suns), an improvement over the previous record, also set by Solar Junction with 43.5 percent (at 418 suns). The hope is that these more efficient compound semiconductors can improve the economics of concentrated photovoltaics.

Vijit Sabnis, VP of Technology and a co-founder of Solar Junction, told GTM in an earlier interview that no other PV technology has the headroom to improve its efficiency like multi-junction solar cells.

Vital stats on Solar Junction:

  • Founded in 2007
  • Headquartered in San Jose, California with 44 employees
  • Pilot production line is approximately 5 megawatts of 500X annual capacity on 4-inch wafers
  • Commissioning a 6-inch production fabrication facility, partially funded by a U.S. DOE SUNPATH contract, with shipments beginning early 2013
  • The firm has raised more than $50 million from ATV, DFJ, NEA and strategic investor and epi-manufacturing partner IQE.
  • Currently holds triple-junction cell efficiency world record of 44.0 percent

CPV has a few tens of megawatts in the field. The largest CPV deployment in North America is the 30-megawatt Alamosa site in Colorado, with hardware from Amonix. The Carlyle Group recently bought that project from Goldman Sachs. Systems manufacturer SolFocus has a project in development in Mexico that could eclipse the Colorado CPV farm. Soitec has large CPV plants in the works and more than 150 megawatts of PPAs with San Diego Gas & Electric and a 50-megawatt plant in South Africa.

But Amonix had to shut down its Las Vegas production facility in July. SolFocus needs more VC. GreenVolts is selling off its assets.

While Greentech Media has observed Demi Moore's law in c-Si progress, Sabnis asserts that M-J solar cells are more able to harness a Moore's law cost and performance progress. He notes that Solar Junction can get two kilowatts from one 4-inch wafer under concentration at 1000 suns and could produce 200 megawatts of power from its relatively small factory floor if fully populated with equipment.

Sabnis cited several studies showing 70 percent theoretical efficiencies from a 5- or 6-junction cell. More practically, he sees 50 percent cell efficiency as being achievable in three to five years, which could get DC module efficiencies to over 40 percent. 

So great technological progress at the CPV cell level is being made by Solar Junction (and Semprius, JDSU, Emcore, and Spectrolab), but vendors have to aggressively cut cost at the systems level to keep up with the plummeting cost of single-axis c-SI. Last week, Barclays quoted a c-Si solar panel spot price of $0.69 per watt.