Perovskites: Is there a reason for concern?
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Energy Sector Analysis
Early studies indicate minimal concern regarding lead in metal halide perovskites, but there is a need for more detailed long-term studies.
Perovskites: Is there a reason for concern? By Prachi Patel Feature Editor Harald F. Krug
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erovskites have recently taken the photovoltaic research world by storm. The materials promise solar cells that deliver highest possible efficiencies at lowest possible cost. In the three years leading to 2015, confirmed efficiency claims have passed 20%, with more room for improvement. Silicon solar cells took decades to make that climb. Their unprecedented PV performance has put perovskites in the limelight. But perovskites are an old material family known for over a century. The term stands for any natural or synthesized compound with the crystal structure of calcium titanate and the chemical formula ABX3. Hundreds of materials adopt this structure, and they have a variety of properties, including semiconducting, piezoelectric, and thermoelectric. Oxford Photovoltaics, a UK start-up, says that perovskite solar cells could be on the market by 2017. The use of perovskite materials could soar in the next decade. And not just for solar. The most widely used piezoelectric material for sensors and actuators is the ceramic perovskite lead zirconate titanate (PZT), and its market is escalating, thanks to the advanced engineering of its properties and an ever-larger use of sensors in the automotive industry and in medical and other electronics. With this increasing use comes a concern for safety. Most commonly used perovskites contain the well-known toxin lead; methylammonium lead iodide is the material of choice for solar cells. Yet, peer-reviewed literature on the potential toxicity of perovskites and their behavior in biological systems or the environment is rare. “You have a toxic element like lead, and studies haven’t been performed yet on what the problems can be, so of course you have to be concerned,” said Michael McGehee, professor of materials science and engineering at Stanford University. “There is a very small chance that a panel would leak. It’s probably not a show stopper. But on the other hand, I wouldn’t say there are no concerns at all and we shouldn’t worry about it.” A consortium of experts within the four-year European Union-funded FutureNanoNeeds project is now investigating
Harald F. Krug, Swiss Federal Laboratories for Materials Science and Technology Prachi Patel, [email protected]
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MRS BULLETIN
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VOLUME 40 • AUGUST 2015
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www.mrs.org/bulletin • Energy Quarterly
the health risks and dangers of lead-based perovskite materials. The team, led by Michael Graetzel at the Swiss Federal Institute of Technology in Lausanne, is studying every possible scenario through which perovskite nanomaterials could enter the soil and groundwater, reach the food chain, and affect biological systems. “It’s a question of diligence,” said Kenneth Dawson, the director of the Center for BioNano Interactions in Ireland who is coordinating FutureNanoNeeds. “
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