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Lead-Free Perovskite Solar Cells

For low-cost photovoltaics, an ammonium tin halide salt offers a lead-free alternative to current perovskite materials

by Mitch Jacoby
May 12, 2014 | A version of this story appeared in Volume 92, Issue 19

Solar power enthusiasts have been riding on a wave of recent reports describing increasingly impressive performance of perovskite-based solar cells. The devices, which feature light-absorbing organometal halide materials with the perovskite crystal structure, are promising because they are efficient at converting sunlight to electricity and are relatively inexpensive to make. But one shortcoming still hinders the field: Nearly every study focuses on lead-based perovskites. To address concerns of possible lead toxicity, Northwestern University researchers have come up with a way to get the lead out. A team headed by Mercouri G. Kanatzidis and Robert P. H. Chang prepared solar cells featuring methylammonium tin iodide, CH3NH3SnI3, an air-sensitive lead perovskite analog that is normally incompatible with other solar-cell components (Nat. Photonics 2014, DOI: 10.1038/nphoton.2014.82). The team adjusted its fabrication methods to work around the air-sensitivity problem and achieved sunlight-to-electricity conversion efficiencies of nearly 6% in prototype devices. They also discovered that the devices’ absorption profiles can further be tuned to capture more of the visible portion of the spectrum by using mixed iodide-bromide perovskites. Kanatzidis believes that with further study the efficiencies can easily be boosted to 15% to match values already achieved using lead perovskites.

An electron micrograph highlights the layers that make up a tin-based perovskite solar cell.
Credit: Adapted From Nat. Photonics
This SEM image depicts the layered structure of a tin perovskite-based solar cell.


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