EPFL scientists have developed a new solution to reduce the hazards posed by lead in perovskite solar cells.
They have added a transparent phosphate salt to the halide perovskites mixture which does not interfere with light-conversion efficiency and also helps prevent lead from seeping into the soil in cases of solar panel failure.
“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 EPFL professor László Forró.
“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.”
One reason why halide perovskites aren’t that popular yet is because their lead dissolves in water.
This water solubility and solubility in other solvents is actually a great advantage, as it makes building perovskite solar panels simpler and inexpensive.
But the water solubility of lead can become a real environmental and health hazard when the panel breaks or gets wet when it rains.
This is one reason why regulatory authorities aren’t that keen on approving the production of perovskite solar cells on a large, commercial scale.
Finding a way to capture that lead before it gets to the soil and then recycling it as much as possible, as been a focal point of numerous researches of late.
Some efforts have resulted in non-water-soluble and lead-free perovskites but these have yielded poor performance.
Forró’s group has now shown how using a transparent phosphate salt does not lead to solar light blockage nor any dip in performance.
Moreover, 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.
What’s more, it can be recycled too.
According to EPFL chemist Márton Kollár, this ‘fail-safe’ chemistry keeps lead ions from leaching out and can render perovskite devices safer to use in the environment or close to humans.
Image and content: EPFL