When the Biden administration announced in late March a $ 128 million initiative to improve solar energy costs, a significant portion of the money went to research materials named after an obscure 19th-century Russian geologist and nobleman: Lev Perovski .
Among the projects listed: $ 40 million for research and development in so-called perovskite materials that scientists use to push the limits of how efficient and adaptable solar cells can be.
And while perovskites are nothing new – they were first found in the Ural Mountains of Russia in 1839 and are relatively common – their latest applications in solar energy technology have raised hopes that humans will use them to make better use of thousands of megawatts of energy from the sun falling on Earth every hour.
“Perovskites, I would argue, are one of the most exciting opportunities for solar cells in the immediate future,” said David Mitzi, a professor of mechanical engineering and materials science at Duke University who has been studying materials since the 1990s.
Any new solar energy technology had to compete with silicon solar cells, an ingrained technology used for more than 50 years, Mitzi said. But perovskites have the potential both to increase the efficiency of silicon cells and to compete directly with them: “I think there are certainly opportunities.”
Efficiency is just one of the features. Perovskite cells can be easily manufactured in a variety of power-generating materials and at much lower temperatures – and therefore potentially lower – than silicon cells. But the stability and durability of perovskite cells will have to be addressed before they can completely replace silicon.
Scientists have now discovered a whole class of perovskite materials that share a specific structure, incorporating three different chemicals into a cubic crystal shape. They recognized years ago that some perovskites were semiconductors, such as silicon used in electronics. But it wasn’t until 2009 that researchers discovered that perovskites could also be used to build solar cells, which turn sunlight into usable electricity.
The first perovskite cells had a very low efficiency, so most of the sun that fell on them was not used. But they improved quickly.
“The efficiency with which solar cells containing these perovskite materials convert sunlight into electrons has increased at a truly incredible rate, as the efficiency is now close to that of silicon solar cells in the laboratory,” said Lynn Loo. professor of chemical engineering at Princeton University and director of the Andlinger Center for Energy and the Environment. “That’s why we’re so excited about this class of materials.”
Perovskite solar cells can also be manufactured relatively easily – unlike silicon cells, which must be refined at very high temperatures and therefore need a lot of energy to produce. Perovskites can be made as thin sheets at low temperatures or as inks that can be effectively “printed” on substrates of other materials, such as flexible plastic rolls.
This could lead to their use on surfaces where silicon solar cells would not be practical, such as the exterior of cars or trucks; or they can even be printed on canvas to power wearable electronics. Another possibility is to apply thin films of perovskite to the window glass, where it would let most of the light in while using some of it to generate electricity.
But one of the most promising uses of perovskite cells is to combine them with silicon cells so that they use more solar energy than silicon alone. The best silicon cells approach their maximum theoretical efficiency of about 29%. But perovskite cells can be adjusted to generate electricity from light wavelengths that silicon cells do not use – and so coating silicon solar cells with semi-transparent films of perovskite cells could exceed this fundamental limit.
Physicist Henry Snaith of Oxford University, a leading researcher in perovskite solar cells, sees this as a way to combine the industrial dominance of silicon with the technological advantages of perovskites. He believes that “tandem” silicon and perovskite cells with an efficiency of over 40% efficiency could be commercially spread within 10 years and that they could soon be followed by multilayer cells with efficiencies of over 50%.
The potential of perovskite solar panels has also attracted the attention of the government, both here and abroad. In addition to creating new business opportunities for US companies, perovskites could become a relatively inexpensive way for solar energy to cause fossil fuels to generate electricity. “I think many of us have aspirations for technology to really start addressing some of the climate change issues that need to be addressed by 2050,” said physicist Joe Berry, who leads solar perovskite research at Golden’s National Renewable Energy Laboratory. , Colorado.
However, perovskite solar cells still face problems, and the key to these is the issue of stability. In part, because they are easy to make, perovskite cells also degrade rapidly from moisture and heat. Some experimental perovskite cells have remained stable for tens of thousands of hours, but they still have a long way to go to meet the 25 or 30 years of silicon cell use, Snaith said.
Some of the most promising perovskite materials for solar energy also incorporate lead, which can be released into the environment when perovskite cells degrade. Researchers are studying alternatives to lead-based perovskites, such as tin-based perovskites and similar crystalline structures that incorporate other safer substances.
“I think there are some more challenges,” Loo said. “If [perovskites] will play a significant role depending on whether we can overcome these challenges. ”