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https://www.bbc.com/news/business-51799503

Today's average commercial solar panel converts 17-19% of the light energy hitting it to electricity. This is up from 12% just 10 years ago. But what if we could boost this to 30%? More efficient solar cells mean we could get much more than today's 2.4% of global electricity supply from the sun.

Solar is already the world's fastest growing energy technology. Ten years ago, there were only 20 gigawatts of installed solar capacity globally - one gigawatt being roughly the output of a single large power station. By the end of last year, the world's installed solar power had jumped to about 600 gigawatts.

[...] But wafer-based crystalline silicon is bumping pretty close to its theoretical maximum efficiency. The Shockley-Queisser limit marks the maximum efficiency for a solar cell made from just one material, and for silicon this is about 32%. However, combining six different materials into what is called a multi-junction cell can push efficiency as high as 47%.

[...] Another way to break through this limit, is to use lenses to magnify the sunlight falling on the solar cell, an approach called concentrated solar. But this is an expensive way to produce electricity, and is mainly useful on satellites. "Not anything you would see on anybody's roof in the next decade," laughs Dr Nancy Haegel, director of materials science at the National Renewable Energy Laboratory in Boulder, Colorado.

[...] The fastest improving solar technology is called perovskites - named after Count Lev Alekseevich von Perovski, a 19th Century Russian mineralogist. These have a particular crystal structure that is good for solar absorption. Thin films, around 300 nanometres (much thinner than a human hair) can be made inexpensively from solutions - allowing them to be easily applied as a coating to buildings, cars or even clothing. Perovskites also work better than silicon at lower lighting intensities, on cloudy days or for indoors. You can print them using an inkjet printer, says Dr Konrad Wojciechowski, scientific director at Saule Technologies, based in Oxford and Warsaw. "Paint on a substrate, and you have a photovoltaic device," he says.

[...] From such small gains - to the use of concentrated solar and perovskites - solar tech is in a race to raise efficiency and push down costs. "Spanning this magical number 30%, this is where the solar cell industry could really make a very big difference," says Swift Solar's Max Hoerantner.

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