Science for our
Nation's
Energy Future

Energy Frontier Research Center

Community Website
Frontiers in
Energy Research
Newsletter
April 2012

Fool’s Gold: From Deception to Innovation

From failure of pyrite to the discovery of new solar cell materials

Robert S. Kokenyesi

Scientists, much like gold miners, have been misled by iron pyrite’s golden promise. Researchers at the Center for Inverse Design have found the reason for the failure of iron pyrite to generate electricity from sunlight, and in the process discovered a similarly abundant material to take its place: iron silicon sulfide.

Pyrite, or fool’s gold, has long been proposed as a viable solar material because of its outstanding capability to absorb light. This common iron-sulfide mineral has the potential to create devices that could use up to 2,000 times less material than conventional solar cells. Yet, the promise of pyrite has not been fulfilled after decades of effort— it just did not work! Inspired by the discovery of flaws present in pyrite, the Center for Inverse Design team identified new materials, such as iron silicon sulfide or Fe2SiS4, which retain most of the advantages but none of the problems.

"Iron is about the cheapest element in the world to extract from nature, silicon is second, and sulfur is virtually free," says Douglas Keszler, a professor at Oregon State University leading the experimental study. "These compounds are stable, safe, and do not decompose. There's nothing yet that looks like a show-stopper in the creation of a new class of solar energy materials." 

A theoretical study, conducted by Liping Yu and Alex Zunger, supported key insights into the underlying problem with pyrite: it decomposes and coexists with metal-like phases, an undesirable property in solar cells. This might have been the end of the story in the conventional “pick a material and learn its properties” approach to materials research.

However, Center for Inverse Design scientists applied a novel discovery mode to identify and develop new, potentially game-changing materials and functionalities: select a property and find or design materials that have it. The team formulated a set of design rules to avoid the problems inherent to pyrite, while preserving its attractive properties. The result? Recognition of a different class of iron-sulfur compounds for solar conversion. Scrutiny by theory and experiment reported in Advanced Energy Materials provides evidence of desired stability and absorption of solar radiation in these materials and further studies are underway.

The Center for Inverse Design team continues to identify and design new earth-abundant materials, like iron silicon sulfide, to achieve this goal. Efficient harvesting of energy supplied by the sun is essential to reducing the cost of solar conversion devices and their extensive deployment, thereby securing the future energy demands of our nation and the world.

More Information

Yu L, S Lany, R Kykyneshi, V Jieratum, R Ravichandran, B Pelatt, E Altschul, HAS Platt, JF Wager, DA Keszler and A Zunger. 2011. “Iron Chalcogenide Photovoltaic Absorbers.” Advanced Energy Materials 1(5):748-753. DOI: 10.1002/aenm.201100351

Acknowledgments

Center for Inverse Design, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences supported this work.

About the author(s):

  • Robert S. Kokenyesi is a postdoctoral researcher at Oregon State University and a member of the Center for Inverse Design. His research interests include design and synthesis of materials for solar energy conversion and fuel-generation devices based on recognizing structural motifs leading to goal functionality.

All that Glitters: Sunlight and Fake Gold

Study shows that related compounds could open the doors for solar harvesting

Scientists, much like gold miners, have been misled by iron pyrite’s golden promise. Researchers at the Center for Inverse Design have found the reason for the failure of iron pyrite to generate electricity from sunlight, and in the process discovered a similarly abundant material to take its place: iron silicon sulfide.

More effective, less expensive solar cells could reduce the need for imported fossil fuels in the United States and elsewhere. Solar cells present a direct route to convert sunlight, absorbed in a material, into electricity. To make more efficient cells, scientists have been drawn to fool’s gold, known scientifically as iron pyrite. Theoretically, it could be used to build more efficient solar cells with fewer resources. But, the material converts light far less effectively than predicted. Scientists discovered that pyrite fails because it decomposes, leading to an inefficient metal-like phase. Inspired by this discovery, the team identified two new compounds, takeoffs on iron pyrite, which are stable and safe. Scrutiny by theory and experiment provided evidence of desired stability and absorption of solar radiation in these materials. The Center for Inverse Design, led by the National Renewable Energy Laboratory, conducted the research.

Written by Robert S. Kokenyesi and Kristin Manke

More Information

Yu L, S Lany, R Kykyneshi, V Jieratum, R Ravichandran, B Pelatt, E Altschul, HAS Platt, JF Wager, DA Keszler and A Zunger. 2011. “Iron Chalcogenide Photovoltaic Absorbers.” Advanced Energy Materials 1(5):748-753. DOI: 10.1002/aenm.201100351

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.