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Researchers are turning toxic, centuries-old ammunition into highly efficient and cheap solar panels.
Hundreds of years ago, lead musket balls tore across European battlefields, littering the ground with toxic materials. Today, a team of scientists in Germany has scavenged a pile of this deeply tarnished, centuries-old ammunition off eBay to forge a radically different technology. They melted down the munitions and transformed them into precursor materials for solar panels.
Manufacturers require massive amounts of extremely pure lead to build perovskite solar cells, a cheap and powerful class of energy devices. Mining for new lead ravages the environment and exposes workers to toxins. By successfully harvesting clean power from degraded scrap (not just old spent bullets), researchers offer a viable, closed-loop path to scale up green grids while cleaning up historical environmental sins.
What were once spent weapons of war have now found a second life within renewable technology.
Silicon dominates the global solar market, but perovskite crystals are rapidly gaining ground. Manufacturers can print these adaptable structures onto flexible plastics, printing them directly onto lightweight fabrics.
The secret to their performance lies in a highly adaptable molecular shape. “You can mix and match atoms and molecules into the structure,” Tonio Buonassisi, director of MIT’s Photovoltaics Research Laboratory, told MIT News in 2022. “Perovskites are highly tunable, like a build-your-own-adventure type of crystal structure.”
While scientists can construct these crystal structures using a variety of elements, lead remains the undisputed champion. So far, lead-free alternatives have generally not matched the efficiencies achieved by lead-based perovskites.
Yet, relying on a toxic heavy metal creates a severe dilemma for green energy. “Perovskite solar cells rely on high-purity lead iodide,” physicist and study co-author Ian Marius Peters wrote on LinkedIn. “But lead is both toxic and resource-intensive to mine and refine.”
To find a cleaner path forward, researchers at the Jülich Research Centre sought out the most challenging raw material available. The musket fragments were tainted with carbon residue, thick layers of surface oxidation, and centuries of dirt. The scientists reasoned that extracting high-purity lead from such a contaminated source would prove they could recycle almost any modern lead waste.
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The team designed a two-step salvage operation that aims to reduce the severe environmental costs of traditional recycling. Standard industrial methods dissolve lead in nitric acid, generating massive amounts of contaminated wastewater.
Instead, the researchers melted the antique musket balls with the help of electrical contacts. They submerged these metal rods into a liquid bath containing a chemical solvent and dissolved iodine. By running an electrical current through the liquid, they oxidized the metal and stripped away impurities. This approach produced a bright yellow powder called lead iodide with 94% efficiency.
Even after the electrical bath, the raw powder still carried tiny, lingering traces of its past life—minuscule flecks of copper, silver, and zinc. Modern solar panels, however, demand flawless ingredients. To achieve that extreme purity, the scientists dissolved the powder into a liquid and slowly cranked up the heat. As the temperature rose, the pure molecules naturally snapped together to form high-purity crystals. As these crystals grew, they physically squeezed out the unwanted metallic hitchhikers, leaving behind only the pristine material needed to capture sunlight.
The final product reached a purity level of 99.999%, an industry standard known as “five nines”.
The ultimate test arrived when the team used the recycled material to fabricate functioning perovskite solar cells. Devices constructed from the ancient weapons converted roughly 21% of the sunlight they received into electricity.
This performance level is statistically indistinguishable from control cells built entirely from pristine, commercial lead. Hitting the 21% mark with heavily contaminated waste proves the industrial viability of the technique.
The authors argue that heavy industry abandons up to 40% of all lead waste. Electronic waste alone dumps millions of tons of the metal into the environment annually. The research team envisions a future where this toxic refuse never reaches a landfill.
“Millions of tons of lead already exist in waste streams that remain underutilized,” Peters added. “This work shows that toxic legacy waste can become a resource for clean energy.”
The study was published in the journal Cell Reports Physical Science.
Aerospace engineer with a passion for biology, paleontology, and physics.
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© 2007-2025 ZME Science – Not exactly rocket science. All Rights Reserved.
