Materials scientists say they have taken a nearly 300-year-old stash of toxic waste—spherical lead bullets from the 16th and 17th centuries, stained with carbon residue, metal impurities and dull oxidation—and turned them into a critical component for solar panels.
And not just any solar panels, but perovskite solar panels: one of the most Affordable and energy efficient forms of solar energy on the market today.
Researchers at the Jülich Research Center in Erlangen, Germany, said their new technique turns highly contaminated lead bullets into the high-purity, commercial-grade lead iodide needed in bulk to produce the best of these perovskite solar cells. The team’s results produced solar panels capable of converting sunlight into electricity with a competitive efficiency of 21%. for contexttopline perovskite solar cells made with cleaner starting ingredients currently harvest energy at just over 27% efficiency.
“Perovskite solar cells are based on high-purity lead iodide,” said physicist and study co-author Ian Marius Peters. post on LinkedIn sharing your research“but lead is both toxic and resource-intensive to produce and refine.”
“Millions of tons of lead exist in waste streams that are no longer being used,” Peters said. “This work shows that toxic legacy waste can be turned into a clean energy source.”
Remove the leader
Peters and his colleagues first chose this pile of time-destroyed ammunition from Renaissance muskets and arquebuses as a proof of concept for their new method. According to their new study, has been published This March in the journal Cell Reports Physical Science, they bought “pieces of a musket ball” (like you, probably) from someone on eBay. They wrote that the bullets were deliberately chosen as “extraordinarily difficult model raw materials” for the production of high-purity lead iodide. They did this, in other words, to clearly prove that their process would work on really dirty old lead full of chemical impurities.
Their improvement method consists of two main steps. First, two electrodes made of melted and reshaped lead bullets were immersed in a mixture of acetonitrile solvent and dissolved iodine with an electric current passing through this liquid bath. The process produced lead iodide of remarkably high purity, according to the team. The team also noted that this new method also has environmental benefits, limiting chemical use and producing less lead-contaminated wastewater.
In a second step, this mustard yellow and highly pure lead iodide powder was used to grow perovskite crystals. technique known as inverse temperature crystallization – it uses heat rather than cold to induce the correct formation of molecules and crystal forms.
According to Peters, this inexpensive refinement method yielded perovskite solar cells that were “statistically indistinguishable from devices made with commercial 5N precursors.” (5N here is industry jargon for a material with 99.999% purity. If you believe that, and I’ll admit I struggle myself, 5N short for “five to nine”.)
Closing the loop
The researchers said they implemented the project as a means of capturing the “estimated 30% to 40% of lead waste” that is effectively abandoned at the end of the industrial life cycle. To increase the production of perovskite solar cells (PSCs), an entirely new system similar to the efficient recycling of lead-acid car batteries will be needed.
“Sustainable lead sources are essential for scaling up PSCs,” the authors wrote.
Perovskites are a broad category of solar cells that don’t necessarily require lead in their crystalline structure to function, but lead-based versions have proven to be the most efficient at converting sunlight into electricity.
“Over time, lead-based devices continue to improve their performance,” said Tonio Buonassisi, director of MIT’s Photovoltaic Research Laboratory. he said In 2022, MIT News stated that “none of the other compositions came close in terms of electronic performance.”
According to Buonassisi, lead halide perovskite solar cells have been the focus of perovskite researchers for more than a decade. Among the material’s many advantages over traditional silicon-based solar panels, perovskites can be easily woven. fabric-like solar cells made of incredibly light and flexible polymer materials. Hybrid perovskite-silicon solar panels can also be made by mixing perovskites. achieved an impressive 36% efficiency, greater than either.
“You can mix and match atoms and molecules into a structure,” noted Buonassi. “Perovskites are highly tuned as their own kind of adventure in crystal structure.”
