Stacked solar cells and 70,000 suns

Researchers at North Carolina State University have found a promising way to drastically improve the energy efficiency of stacked solar cells, and indirectly reduce their costs.

Stacked solar cells are currently the most efficient solar power generators available and manufacturers are trying to increase their efficiency by adding lenses that concentrate the power hitting them to the equivalent of 4,000 suns or more.

However, there’s a hitch. When the solar energy is concentrated to 700 suns or more the junctions between the stacked cells begin losing voltage and waste the energy as heat.

The new researchers at North Carolina State have found that by inserting a think film of gallium arsenide into the connection between the cells there is virtually no loss of voltage.

In a report in phys.org, Dr. Salah Bedair, a professor at the university who is the senior author of a paper about the research, said: “Now we have created a connecting junction that loses almost no voltage, even when the stacked solar cell is exposed to 70,000 suns of solar energy. And that is more than sufficient for practical purposes, since concentrating lenses are unlikely to create more than 4,000 or 5,000 suns worth of energy. This discovery means that solar cell manufacturers can now create stacked cells that can handle these high-intensity solar energies without losing voltage at the connecting junctions, thus potentially improving conversion efficiency.”

The researchers also point out that the use of lenses to concentrate energy in solar cells would mean they could be manufactured at a smaller size, which would be more economic. And “concentrating lenses are relatively inexpensive,” Bedair said.

To read the article in phys.org, click here.