New “tandem” solar cell breaks world record

Researchers in Saudi Arabia have just broken a record they themselves set just two months ago: a tandem solar cell with an unprecedented 33.7% efficiency.

The challenge: Photovoltaic solar cells absorb light and convert it into electricity. You’ll find dozens of them in the average solar panel, and chances are they’ll be made from silicon, because it lasts a long time and is relatively cheap.

Silicon solar cells aren’t terribly efficient, though — most commercial silicon cells convert just 18-22% of the solar energy that hits them into electricity. That means you need more cells and more panels, increasing the cost and upkeep of the system. 

The idea: To improve the efficiency of solar cells, some researchers are pairing the silicon in them with another material. In December 2022, for example, a team from Germany unveiled a solar cell consisting of the standard silicon with a layer of the mineral perovskite on top of it.

While the silicon layer absorbed and converted mostly infrared light into electricity, the perovskite layer did the same for visible light. As a result, the “tandem” solar cell was able to achieve a then-record-breaking efficiency of 32.5%.

What’s new? On May 30, Erkan Aydin, a research scientist at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, announced the creation of a tandem solar cell that achieved 33.7% efficiency.

This breaks the current world record of 33.2%, which the same KAUST researchers set in April 2023.

“In two months’ time, we’ve set a new world record for perovskite/silicon tandem solar cells —  again!” wrote Aydin in a LinkedIn post. “We hope that our new achievement will contribute to accelerating the green energy transition.” 

Black box: KAUST’s tandem solar cell has been certified by the European Solar Test Installation, a research lab that verifies the performance of solar tech for the European Union, so we know its efficiency claims are valid.

However, the researchers have revealed nothing on how they were able to squeeze that extra bit of electricity out of the cells. 

When they broke the record in April, they noted that the silicon part of the cell was textured — that has helped improve efficiency in other tandem solar cells, so they may have taken the same approach with the new cell, but we don’t yet know for sure if that’s the case.

Looking ahead: Creating solar cells that can break efficiency records in the lab is one thing — achieving those same efficiencies with solar cells that could make a difference in the real world is another.

The next steps for the KAUST team will likely involve developing larger versions of their tandem solar cell. The current cell is just larger than one square centimeter, but the cells used in standard solar panels are usually around 240 cm².

KAUST now needs to prove its tandem solar cell can make a difference in the real world.

Approximately 1,200 of those standard silicon solar cells are needed to produce enough electricity for the average home, so, even though KAUST’s cell is more efficient than any other perovskite/silicon tandem solar cell, we’d still need a lot of them to make any sort of dent in the world’s energy needs. 

That means KAUST not only needs to be able to make their cells bigger, they need to be able to manufacture them at scale and at a competitive price. 

Buyers also expect their solar panels to last at least 20 years, but perovskite-based cells tend to degrade more quickly than silicon ones — ensuring that its tandem solar cell can withstand environmental conditions for years will be another important goal for the KAUST team.

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