Efficiency of Silicon Solar Cells Climbs

In research published this week in Nature Energy, researchers at Kaneka Corp., a resin and plastics manufacturer based in Osaka, describe the first silicon solar cell to achieve a record-breaking 26.3 percent efficiency—a 0.7 percent increase over the previous record.  That may not seem like a lot, but it’s really a big step when you consider that silicon solar cells’ theoretical maximum efficiency is just 29 percent.

Kaneka is a member of a project set up by the New Energy and industrial Technology Development Organization (NEDO), a Japanese government entity established to help develop and promote new energy technologies.

In producing its new 180.43-square-centimeter monocrystalline silicon prototype cell, Kaneka further developed and improved on several of the technologies promo0ted by NEDO.  Chief among them is Kaneka’s proprietary heterojunction technology.  It reduces recombination, or resistive loss, where instead of exiting the device to produce electricity, positive and negative charges in the solar cell combine and produce heat.

In addition, the company improved the energy-collection efficiency of the solar cell’s interdigitated electrodes.  But even more important, Kaneka moved the grid of electrodes from the front of the cell—the light-receiving area—to the back, boosting the amount of sunlight entering the cell, thereby reducing losses in the optics. 

Panasonic, a member of the same NEDO project and holder of the previous energy-conversion-rate record of 25.6 percent for its 143.7-cm2 solar cell set in 2014, employed the same key features in its device, namely heterojunction with interdigitated back contacts (HJ-IBC).

“But there are many types of materials, manufacturing processes, and architectures that can be selected,” says Kunta Yoshikawa, a member of the Kaneka research team that worked on the new solar cell.  “We achieved 26.3 percent efficiency by developing our CVD (chemical vapor deposition) technology, optical management, and electrical-contact technology using thin-film silicon and our [heterojunction] technology.”

Read more at Efficiency of Silicon Solar Cells Climbs