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.
