Scientists determine the critical obstacle preventing fool’s gold from being used in solar cell construction

The continued proliferation of photovoltaic cells demands that scientists find additional materials outside of the traditional silicon that can efficiently convert sunlight into electricity while simultaneously providing cost efficiency. Photovoltaic cells based on silicon require relatively thick coating of film, making the process costly and energy-intensive, whereas a film of iron pyrite, could be 1,000 times thinner than silicon while still capable of efficiently absorbing sunlight.

One key material currently investigated by scientists from the University of Wisconsin-Madison that can theoretically accomplish this task, when it works, is iron pyrite— otherwise known as fool’s gold. The team thinks they’ve gotten a grasp on why the mineral may be proving difficult to work with. 

Iron and sulfur, the compounds that make iron pyrite, are just as abundant in the Earth’s crust as is silicon, so constructing solar cells from this material could potentially have a massive cost advantage in a large scale development. Furthermore, previous research has determined theoretical efficiency, materials availability, and extraction cost place iron pyrite as a primary candidate for economical photovoltaic materials. 

Photovoltaic cell efficiency is determined by three parameters, and iron pyrite possess all but one: voltage. To determine why its photovoltage coefficient was so low, the scientists looked at inside the material, not on the surface of the crystal as previous researchers have done. They determined that a series of what they called “bulk defects,” occur when a sulfur atom is missing its expected place in the crystal structure. This property is inherent to iron pyrite and also present in ultra-pure crystals. Unfortunately, there’s no work around yet, if ever, but at least scientists under “why” such a seemingly photovoltaic material cannot conduct voltage.