Scientists get to the heart of fool's gold as a solar material

As the installation of photovoltaic solar cells continues to accelerate, scientists are looking for inexpensive materials beyond the traditional silicon that can efficiently convert sunlight into electricity.

Pyrite This lump of iron pyrite shows the characteristic cubic crystals of fool’s gold. Defects in pyrite’s crystal structure are an obstacle to building solar cells from the material. UW–Madison Geology Museum

Theoretically, iron pyrite — a cheap compound that makes a common mineral known as fool’s gold — could do the job, but when it works at all, the conversion efficiency remains frustratingly low. Now, a University of Wisconsin–Madison research team explains why that is, in a discovery that suggests how improvements in this promising material could lead to inexpensive yet efficient solar cells.

“We think we now understand why pyrite hasn’t worked,” says chemistry Professor Song Jin, “and that provides the hope, based on our understanding, for figuring out how to make it work. This could be even more difficult, but exciting and rewarding.”

Although most commercial photovoltaic cells nowadays are based on silicon, the light-collecting film must be relatively thick and pure, which makes the production process costly and energy-intensive, says Jin.