Solar panels are reaching their limit. These crystals could change that.
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 into research into materials named after an obscure 19th-century Russian geologist and nobleman: Lev Perovski.
Among the projects listed: $ 40 million for research and development on so-called perovskite materials, which scientists use to push the limits of the efficiency and adaptability of solar cells.
And while perovskites are nothing new – they were first found in the Russian Urals in 1839 and are relatively common – their newer uses in solar technology have raised hope that people will use them to better utilize the thousands of megawatts of energy from the Sun that falls on earth every hour.
“I think perovskites are one of the most exciting opportunities for solar cells in the near future,” said David Mitzi, a professor of mechanical engineering and materials science at Duke University who has studied the materials since the 1990s.
Any new solar technology had to compete with silicon solar cells, an entrenched 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 even compete directly with them: “I think there are definitely opportunities.”
Efficiency is just one of the characteristics. Perovskite cells can be easily fabricated to a variety of power generating materials and at much lower temperatures – and therefore potentially less cost – than silicon cells. However, the stability and durability of perovskite cells must be considered before they can fully replace silicon.
Scientists have now discovered a whole class of perovskite materials that have a specific structure and contain three different chemicals in a cubic crystal form. They realized years ago that some perovskites were semiconductors, like the silicon used in electronics. It wasn’t until 2009 that researchers found that perovskites can also be used to build solar cells that convert sunlight into usable electricity.
The first perovskite cells had very low efficiencies, so most of the sunlight that fell on them was not used. But they improved quickly.
“The efficiency with which solar cells convert sunlight into electrons using these perovskite materials has increased at an incredible rate, so that the efficiencies are 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 Environment. “That is why we are very happy about this class of material.”
Perovskite solar cells can also be manufactured relatively easily – in contrast to silicon cells, which have to be refined at very high temperatures and therefore require a lot of energy. Perovskites can be manufactured as thin films at low temperatures or as inks that can be effectively “printed” onto substrates made from other materials, such as flexible plastic rolls.
This could lead to their use on surfaces where silicon solar cells would not be practical, e.g. B. in the exterior of cars or trucks. or they can even be printed on fabric to power portable electronics. Another option is to apply thin films of perovskites to the glass of windows, where they would let through most of the light and use some of it to generate electricity.
One of the most promising uses for 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 theoretical maximum efficiency of around 29 percent. However, 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 films made from perovskite cells could overcome this fundamental limit.
The physicist Henry Snaith of the University of Oxford, a leading researcher into perovskite solar cells, sees this as an opportunity to combine the industrial dominance of silicon with the technological advantages of perovskites. He believes that tandem silicon and perovskite cells with efficiencies in excess of 40 percent could be commercially widespread within 10 years and that they could soon be followed by multilayer cells with efficiencies in excess of 50 percent.
The potential of perovskite solar panels has caught government attention both here and overseas. In addition to creating new business opportunities for US companies, perovskites could also be a relatively inexpensive way for solar energy to challenge fossil fuels for power generation. “I think a lot of us are striving for technology to really start addressing some of the climate change problems that need to be solved 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 face problems and the key to this is the problem of 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 handle 25 or 30 years of silicon cell use, Snaith said.
Some of the most promising perovskite materials for solar energy also contain lead, which can be released into the environment as perovskite cells break down. Researchers are investigating alternatives to lead-based perovskites such as tin-based perovskites and similar crystal structures that contain other, safer substances.
“I think there are some challenges ahead,” said Loo. “If [perovskites] An important role will depend on whether we can meet these challenges. ”