German and Belgian researchers develop new solar cell with 25% photoelectric conversion efficiency

Researchers in Germany and Belgium have worked together to develop a new tandem calcium titanite/copper indium diselenide (CIS) solar cell with a photovoltaic conversion efficiency of 25%, the highest ever achieved in its class. The solar cell is flexible, lightweight and versatile, promising applications in vehicles, portable devices and foldable devices. The latest research was published in the journal ACS-Energy Letters, a division of the American Chemical Society.

Chalcogenide is a new type of material with a special crystal structure. Over the past decade, calcium titanite solar cells have progressed rapidly to achieve photovoltaic efficiencies comparable to those of the long-established silicon solar cells.

The efficiency of solar cells can be increased by using two or more cells in a stack. If each solar cell in the stack can effectively absorb light from a different part of the solar spectrum, the inherent losses can be reduced and the photovoltaic efficiency of the entire cell can be increased. Due to their "versatility", chalcogenide solar cells have become the "leader" in the field of stacked solar cells. Tandem solar cells using chalcogenide and silicon have achieved photovoltaic efficiencies of up to 29% or more, significantly higher than cells made from chalcogenide (25.7%) or silicon (26.7%) alone.

In the latest study, an international research team led by Dr. Marko Preciado of the Karlsruhe Institute of Technology has successfully produced tandem calcium titanite/CIS solar cells with a photovoltaic conversion efficiency of up to 24.9 percent, the highest photovoltaic conversion efficiency ever achieved with this type of technology.

Combining chalcogenide with other materials such as copper indium diselenide or copper indium gallium diselenide holds the promise of flexible and lightweight tandem solar cells, according to the researchers. Such cells could be mounted not only on buildings but also on vehicles and portable devices, and could even be folded or rolled up for storage and extended when needed, for example on blinds or awnings, to shade the sun while also generating electricity.

The researchers said, "The latest research demonstrates the potential of calcium titanite/CIS tandem solar cells, paving the way for a possible future increase in efficiency to over 30%."