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Efficient solar cells will help mitigate climate change

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The success of scientists in increasing the efficiency of solar cells propels policymakers’ dream of mass production and consumption of energy harnessed using sunlight that will help mitigate climate change.

Scientists have recently developed a solar cell capable of converting sunlight into electricity with substantially higher efficiency. Hitherto solar technology succeeded in producing maximum efficiency around 25 per cent.

The new method works by stacking multiple layers of solar hardware into a single cell. Each layer absorbs a different aspect of the solar spectrum. Stacking solar cells increases efficiency.

A Science Daily report released this week says, “Researchers have produced perovskite/CIS tandem solar cells with an efficiency of nearly 25 per cent. This is the highest value achieved with this technology. This combination of materials is light and versatile. This raises the probability of using these tandem solar cells in vehicles, portable equipment, and foldable devices.”

Perovskite solar cells are thin-film devices built with layers of materials, either printed or coated from liquid inks or vacuum-deposited. Experts now have a better understanding of the stability and degradation of perovskite solar cells. Unfortunately, they are not currently commercially viable because of their limited operational lifespan.

Researchers at the Karlsruhe Institute of Technology (Karlsruher Institut für Technologie) (KIT) in Germany have produced perovskite/CIS tandem solar cells with increased efficiency. They worked with partners in the European Union-funded Percistand Project. The researchers published their results in the journal ACS Energy Letters.

The project aims to develop innovative materials and processes for perovskite on chalcogenide tandem appliances. The project focuses on four-terminal tandem solar cell and module prototype testing on glass substrates. The project aims to obtain efficiency, stability, and large-scale manufacturability of thin film photovoltaic material competitive with existing commercial photovoltaic technologies.

The Science Daily report says, “Perovskite solar cells have made astounding progress over the past decade. Their efficiency is now comparable to that of the long-established silicon solar cells. Perovskites are innovative materials with a special crystal structure. Researchers worldwide are working to get perovskite photovoltaic technology ready for practical applications. The more electricity they generate per unit of surface area, the more attractive solar cells are for consumers.”

Scientists increased the efficiency of solar cells by stacking two or more cells. If the stacked solar cells efficiently absorb light from a different part of the solar spectrum, they noted reduction in inherent losses and increase in efficiency. They define efficiency as a measure of how much of the incident light converts into electricity.

The versatile perovskite solar cells make outstanding components for such tandems. Tandem solar cells using perovskites and silicon have reached a record efficiency level of over 29 per cent, considerably higher than that of individual cells made of perovskite (25.7 per cent) or silicon (26.7 per cent).

An international team of researchers led by Dr Marco A Ruiz-Preciado and tenure-track professor Ulrich W. Paetzold from the Light Technology Institute (LTI) and the Institute of Microstructure Technology (IMT) at KIT has succeeded in producing perovskite/CIS tandem solar cells with a maximum efficiency of 24.9 per cent (23.5 per cent certified).

"This is the highest reported efficiency for this technology and the first high efficiency level reached at all with a nearly gallium-free copper-indium diselenide solar cell in a tandem," says Ruiz-Preciado. Reducing the amount of gallium results in a narrow band gap of approximately one electron volt (eV), which is very close to the ideal value of 0.96eV for the lower solar cell in a tandem.

The team’s study shows the potential of perovskite/CIS tandem solar cells and paves the way for future development to increase their efficiency further.

[Sudeep Sonawane, an India-based journalist, has worked in five countries in the Middle East and Asia. Email: []

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