Lead ammunition from the 17th century as a raw material for modern solar cells? Researchers have implemented what sounds absurd in the laboratory. An electrochemical process converts heavily contaminated lead into highly pure material for perovskite solar cells, which achieve the same level of efficiency as new cells.
What served as a deadly projectile in the 17th century could solve energy problems in the future. Because: Historical lead ammunition is heavily contaminated with carbon residues, metal inclusions and a pronounced patina. Researchers use these contaminated residues as an extreme stress test to test their method for obtaining high-purity PbI2 for photovoltaics. The approach aims to transfer hazardous lead waste into a closed cycle while reducing the need for environmentally polluting primary mining.
Lead ammunition for solar cells: This is how electrolysis works
The transformation begins with the direct anodic oxidation of the metallic lead in an electrolyte. Yellow PbI is formed during electrolysis2-Deposits mainly on the cathode, which makes it much easier to collect the material later.
Compared to classic water-based processes, the process saves PbI per kilogram2 about 50 to 70 liters of water. The researchers demonstrated the sustainability of the laboratory step with a low energy requirement for stirring of just 0.01 to 0.1 kWh per run.
How does lead ammunition become a crystal for solar cells?
To remove the lead from the electrodes, the scientists chemically converted it into a solution. The result was impure perovskite powder. This powder formed the basis for subsequent cleaning using inverse temperature crystallization (ITC).
The PbI dissolved2 in a solvent and is then mixed with another mixture. Only through this chemical combination can the FAPbI required for solar cells be produced under controlled heating3-Single crystals are formed.
The addition of formic acid stabilizes the desired crystal phase and protects the material from oxidation. However, a key point of criticism regarding industrial scalability is the process time of around 70 hours per batch.
With a laboratory productivity of just 0.05 gh-1 This time expenditure currently represents a massive bottleneck. Nevertheless, the process proves that even highly contaminated starting materials can be used for high-tech applications.
Solar cells made from lead ammunition achieve 21 percent efficiency
The solar cells made from recycled lead achieve an efficiency (PCE) of 21 percent in the laboratory. Statistical evaluations show that this performance is absolutely identical to devices made from commercial high-purity material (5N standard).
External quantum efficiency (EQE) measurements also confirm that the recycled material does not cause any spectral power losses. This proves the high selectivity of the crystallization process, which effectively displaces disruptive foreign ions such as copper or silver from the lattice.
According to the researchers, in the future this strategy could also be transferred to mass-relevant waste streams such as old car batteries or roofing lead. Even heterogeneous sources from electronic scrap should be usable for perovskite photovoltaics after appropriate physical pretreatment.
However, the ecological benefits of such a closed loop depended heavily on efficient solvent recovery. Ultimately, a shortening of crystallization times would largely determine the economic attractiveness of this upcycling model.
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