Researchers develop perovskite solar cells that prevent lead from seeping into the soil in cases of solar panel failure.
Perovskite solar cells are very popular solar cells which include a perovskite-structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-capturing active layer. The use of perovskite materials allow for a cheap and easy manufacturing process. Perovskite is therefore a very promising solution for solar harvesting but cells contain lead, which is toxic to the environment and a serious health hazard.
The problem with these cells is that halide perovskites lead can dissolve in water. The solubility in water is actually a great advantage as it makes building perovskite solar panels simpler and inexpensive. But solubility of these lead compounds in water is a serious environmental and health hazard. When these solar cells get wet or when they are disposed of, they emit these soluble lead compounds in the environment.
This issue has gained a lot of attention and researchers across the globe are trying to find solutions for non-soluble perovskites. However, the attempts to synthesize non-water-soluble and lead-free perovskites have yielded poor performance.
Researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) have discovered a way for preventing lead from seeping into the soil in cases of solar panel failure. Their developed technique uses transparent phosphate salt that doesn’t interfere with light-conversion efficiency. The study was published in ACS Applied Materials & Interfaces.
“The solar-energy-to-electricity conversion of perovskite solar cells is unbelievably high, around 25%, which is now approaching the performance of the best silicon solar cells,” says Professor László Forró at EPFL’s School of Basic Sciences. “But their central element is lead, which is a poison; if the solar panel fails, it can wash out into the soil, get into the food chain, and cause serious diseases.”
The EPFL group uses a transparent phosphate salt. If the solar panel fails, the phosphate salt immediately reacts with lead to produce a water-insoluble compound that cannot leach out to the soil. Moreover, it can be recycled.
“The ‘fail-safe’ chemistry keeps lead ions from leaching out and can render perovskite devices safer to use in the environment or close to humans,” says Márton Kollár, the chemist behind the growth of perovskite crystals.
“This is an extremely important study—I would say, a central one—for large-scale commercialization of perovskite-based solar cells.” Forró concludes.