Raising the CPV bar: New efficiency records for solar cells and modules

New Hampshire, USA -- Four months after revealing a record 43.5-percent four-junction concentrated photovoltaic (CPV) cell, a European partnership has added a full point to that mark, touting a new 44.7-percent efficient four-junction CPV cell. The group includes Soitec, the Fraunhofer Institute for Solar Energy Systems (ISE), CEA-Leti, and the Helmholtz Center Berlin.

Adding a full percentage point in just a few months is significant. CPV's value proposition vs. other solar PV technologies is its higher headroom for ratcheting up cell efficiency, which means more output and ultimately translates to lower LCOE at the system level. Traditional solar-PV cells currently top out in the low-20 percent range; other CPV firms are also in the 44-percent range with three-junction CPV cells but this is the first such mark for a four-junction device. (Here's NREL's multithread cell efficiency record/eyetest chart.)

This CPV partnership is rapidly bearing fruit thanks largely to Soitec's background in wafer bonding technology (dubbed "SmartCut," already applied to building semiconductors) and Fraunhofer ISE's experience in epitaxial growth of III-V materials and device characterization, explained Frank Dimroth, project leader on the Fraunhofer side and Jocelyne Wasselin, team leader on the Soitec side. Wafer bonding enables the combination of materials that don't like to be put together into a single high-quality device. They reiterated their target cell efficiency is 50 percent, with various areas of improvements to be made.

Wasselin said demos with this new cell might happen within the next two years, but cautioned that this is currently not an average efficiency, and it'll take more time to get that as a sustainable mark at the system level. Incorporating these new record cells, now and as they approach the 50-percent mark, might require some "minor optimizations, but basically we don't see any issue."

Meanwhile, further down the module and production side of CPV performance, another record appears to have been surpassed: Semprius says it's produced a Fraunhofer ISE-confirmed 35.5-percent efficient high-concentration PV module on a pilot production line at its new plant in Henderson, North Carolina, more than a point-and-a-half improvement from its last mark in 2012, calling it a "record for commercially available solar modules."

Russ Kanjorski, Semprius' VP of business development, points out that this is a production module built on a production line, whereas competitor Amonix's recently proclaimed a 35.9 percent efficient CPV module was a "hero R&D module," he said. Semprius similarly has made a demonstration "hero" HCPV module with 37.1 percent conversion efficiency, which should be third-party-certified "shortly," he said.

The typical path to commercialization of a more efficient PV module generally proceeds thusly: produce a more efficient cell in the lab, then verify and sustain it, then integrate it into a module to create a more efficient module, then prove that more efficient module on a production line in a factory.

http://www.renewableenergyworld.com/rea/news/article/2013/09/raising-the-cpv-bar-new-records-for-solar-cells-and-modules