Heterojunction back contact solar cell achieves 27.09% efficiency in testing

A team of engineers from the LONGi Central R&D Institute in China, working with colleagues at the Shenzhen campus of Sun Yat-sen University, reports that its heterojunction back contact (HBC) solar cell has achieved efficiency up to 27.09% during testing.

In their article published in the journal Natural communicationsThe group describes several techniques they developed to improve the efficiency of the solar cell and how it was constructed.

HBCs are a type of solar cell design that involves placing the main working structure at the back of the cell to allow more sunlight to hit the cell, improving efficiency compared to more standard designs.

Unfortunately, the design was stymied by difficulties in managing the necessary recombination of charge carriers. In this new effort, Chinese researchers say they have overcome these difficulties to create a highly efficient solar cell.

LONGi announced the development of its new high-efficiency HBC solar cell last December, but didn’t give many details: they simply said their work was revolutionary and was done using a laser tool newly developed. In their new paper, the team backs up their claims by noting that its effectiveness has been independently verified by the Hamelin Solar Energy Research Institute.

The research team fabricated their cell using an n-type monocrystalline silicon wafer. On the front side they applied an anti-reflective coating. On the back, they divided the work area into four sections: a spacer region, a hold selection contact, an HSC plus space, and an electron selective contact.

They also used a laser to abrade the cell: the transparent conductive oxide (TCO) layer was deposited by magnetron sputtering. The team used another laser to eliminate the gap, preventing leaks. A final layer of silicon nitride was added to prevent damage to other layers during cell operation.

The researchers tested the cell under what they describe as standard conditions, in which their cell achieved an efficiency of 27.09 percent. They also note that they plan to continue working on their cell, hoping to improve efficiency even further. They suggest that a few changes should increase it to 27.7%.

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