Northwestern researchers are the first to develop an efficient solar cell that uses tin instead of lead perovskite as the harvester of light. The low-cost, environmentally friendly solar cell can be made without fancy equipment or hazardous materials, too.


“This is a breakthrough in taking the lead out of a very promising type of solar cell, called a perovskite,” said Mercouri G. Kanatzidis, an inorganic chemist with expertise in dealing with tin. “Tin is a very viable material, and we have shown the material does work as an efficient solar cell.”


Kanatzidis, who led the research, is the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences.


The new solar cell uses a structure called a perovskite, but with tin instead of lead as the light-absorbing material. Lead perovskite has achieved 15 percent efficiency, a level that tin perovskite should be able to match, and possibly surpass. Perovskite solar cells are being touted as the “next big thing in photovoltaics” and have reenergized the field.


Kanatzidis developed, synthesized, and analyzed the material. He then turned to Northwestern collaborator and nanoscientist Robert P. H. Chang to help him engineer a solar cell that worked well.


Details of the lead-free solar cell are published by the journal Nature Photonics. Kanatzidis and Chang are the two senior authors of the paper.


“Other scientists will see what we have done and improve on our methods,” Kanatzidis said. “There is no reason this new material can’t reach an efficiency better than 15 percent, which is what the lead perovskite solar cell offers. Tin and lead are in the same group in the periodic table, so we expect similar results.”


Perovskite solar cells have been around only since 2008. In 2012, Kanatzidis and Chang reported the new tin perovskite solar cell with promises of higher efficiency and lower fabrication costs while being environmentally safe.


“Solar energy is free and is the only energy that is sustainable forever,” Kanatzidis said. “If we know how to harvest this energy in an efficient way, we can raise our standard of living and help preserve the environment.”


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