When the Biden government announced a $ 128 million initiative to improve the cost of solar energy in late March, a significant portion of the money went towards research into materials named after an obscure 19th-century Russian geologist and nobleman: Lev Perovski.
Among the projects mentioned: $ 40 million for research and development on so-called perovskite materials that scientists use to push the boundaries of how efficient and adaptable solar cells can be.
And while perovskites are nothing new – they were first found in Russia’s Ural Mountains in 1839, and they are relatively common – their more recent applications in solar technology have sparked hope that humans will use them to power the thousands of megawatts. better use of energy. energy from the sun that falls to Earth every hour.
“Perovskites, I would say, are one of the most exciting possibilities for solar cells in the near future,” said David Mitzi, a professor of mechanical and materials engineering at Duke University who has been studying the materials since the 1990s.
Any new solar technology had to compete with silicon solar cells, a deep-rooted technology that has been in use for more than 50 years, Mitzi said. But perovskites had the potential to both improve the efficiency of silicon cells, and perhaps compete directly with them: “I think there are certainly opportunities.”
Efficiency is just one of the features. Perovskite cells can be easily fabricated into a variety of electricity generating materials and at much lower temperatures – and thus potentially lower costs – than silicon cells. But the stability and durability of perovskite cells will have to be addressed before they can fully replace silicon.
Scientists have now discovered a whole class of perovskite materials that share a specific structure, with three different chemicals in a cubic crystal shape. Years ago they recognized that some perovskites were semiconductors, such as the silicon used in electronics. But it wasn’t until 2009 that researchers discovered that perovskites could also be used to build solar cells, which convert sunlight into usable electricity.
The first perovskite cells had very low efficiency, so most of the sunlight that fell on them was not used. But they have improved quickly.
“The efficiency with which solar cells containing these perovskite materials convert sunlight into electrons has increased incredibly quickly, to the extent that the efficiency is now close to that of silicon solar cells in the lab,” said Lynn Loo, a professor. of chemical engineering from Princeton University and the 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 are also relatively easy to make – unlike silicon cells, which have to be refined at very high temperatures and therefore require a lot of energy to make. Perovskites can be made as thin sheets at low temperatures, or as inks that can be effectively “printed” onto substrates of other materials, such as flexible rolls of plastic.
That could lead to their use on surfaces where silicon solar cells would not be practical, such as the exteriors of cars or trucks; or they can even be printed on fabric to power portable electronics. Another option is to apply thin films of perovskite to the glass of windows, where they allow most of the light to pass through, while some of it is used to generate electricity.
But one of the most promising uses for perovskite cells is to combine them with silicon cells so that they use more solar energy than just silicon. The best silicon cells are approaching their theoretical maximum efficiency of about 29 percent. But perovskite cells can be tuned to generate electricity from wavelengths of light that silicon cells don’t use – and so covering silicon solar cells with semi-transparent perovskite cell films could overcome that fundamental limit.
University of Oxford physicist Henry Snaith, a leading perovskite solar cell researcher, sees this as a way to combine the industrial dominance of silicon with the technological advantages of perovskites. He thinks that “tandem” silicon and perovskite cells with an efficiency of more than 40 percent could be commercially widespread within 10 years, and could soon be followed by multilayer cells with an efficiency of more than 50 percent.
The potential of perovskite solar panels has also caught the attention of the government, both here and abroad. In addition to creating new commercial opportunities for US companies, perovskites could become a relatively inexpensive way for solar to challenge fossil fuels to generate electricity. “I think many of us have the ambition to really start using the technology to tackle some of the climate change issues that need to be addressed by 2050,” said physicist Joe Berry, who leads research on solar perovskites at the National. Renewable Energy Laboratory in Golden, Colorado.
However, perovskite solar cells still have problems, the most important of which is stability. In part because they are easy to make, perovskite cells are also quickly broken down by 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 use of silicon cells, Snaith said.
Some of the most promising solar perovskite materials also contain lead, which can be released into the environment when the perovskite cells are broken down. Researchers are studying alternatives to lead-based perovskites, such as tin-based perovskites, and similar crystal structures that incorporate other, safer substances.
“I think there are some challenges ahead,” said Loo. “Or [perovskites] play an important role depends on whether we can overcome these challenges. ”