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NEWS
First Step Taken Toward Nontoxic Solar Cells
July 31, 2019

Solar panel installations are on the rise in the U.S., with more than 2 million new installations in early 2019, the most ever recorded in a first quarter, according to a recent report by Solar Energy Industries Association and Wood Mackenzie Power & Renewables.


An atomic model of KBaTeBiO6 (left), the most promising of 30,000 oxides in a potential solar panel. At right is a scanning transmission electron micrograph showing the atomic structure of KBaTeBiO6, along with snapshot of the synthesized powder. Credit: Rohan Mishra

To meet the ever-increasing demands, low-cost and more efficient alternatives to silicon-based solar cells — currently the most widely used technology — are desirable. In the past decade, lead-halide perovskites have surged as the most promising class of alternative materials; however, they are unstable. They contain lead, which is toxic and poses potential health and environmental hazards such as groundwater contamination.

According to information, a team of engineers at Washington University in St. Louis has found what they believe is a more stable, less toxic semiconductor for solar applications using a novel double perovskite oxide discovered through data analytics and quantum-mechanical calculations.

Their work was published online recently in Chemistry of Materials.

Rohan Mishra, assistant professor of mechanical engineering & materials science in the McKelvey School of Engineering, led an interdisciplinary, international team that discovered the new semiconductor, made up of potassium, barium, tellurium, bismuth and oxygen (KBaTeBiO6). The lead-free double perovskite oxide was one of an initial 30,000 potential bismuth-based oxides. Of those 30,000, only about 25 were known compounds.

Using materials informatics and quantum mechanical calculations on one of the fastest supercomputers in the world, Arashdeep Singh Thind, a doctoral student in Prof. Mishra’s lab based at Oak Ridge National Laboratory, found KBaTeBiO6 to be the most promising out of the 30,000 potential oxides.

“We found that this looked to be the most stable compound and that it could be synthesized in the lab,” Prof. Mishra said. “More importantly, whereas most oxides tend to have a large band, we predicted the new compound to have a lower band gap, which is close to the halide perovskites, and to have reasonably good properties.”

Prof. Mishra said these are first-generation solar cells that need more fine tuning of the band gap, but it is a good first step toward nontoxic solar cells.

“This shows that we can go away from these lead-halide perovskites,” Prof. Mishra said. “This opens up a really big space for designing semiconductors not just for solar cell applications but also for other semiconductor applications, such as LCD displays.”

Next, the team will study the role of any defects in this new semiconductor and look to more advanced synthesis techniques, including using aerosol techniques.


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