Cyrus Wadia is Using Pyrite to Grow Nanocrystals for Cheaper Photovoltaics
Fool’s gold, also called pyrite or iron sulfide, can be unearthed just about anywhere, from the hills of California to the villages of Yunnan Province in China. But instead of digging pyrite up, researcher Cyrus Wadia is making pure nano particles of the compound from iron and sulfur salts in his lab at the University of California, Berkeley. His ultimate goal is to turn fool’s gold into real treasure: an inexpensive solar cell.
Today, most solar cells are made of silicon, but they are expensive: though silicon is abundant, turning it into photovoltaics requires extensive, energy-intensive processing. Materials such as cadmium telluride and copper indium gallium diselenide are simpler to process, yielding thin-film cells that cost less to produce. But the elements needed to make these compounds, such as tellurium and gallium, are too rare to meet global energy demands.
So Wadia did a study of possible solar-cell materials, examining not only their chemistry and physics but also their availability. One of the standouts was fool’s gold: it is abundant and cheap, and it has optical properties that allow it to efficiently convert sunlight into electricity. “The theoretical efficiency of iron sulfide is 31 percent. That’s as good as silicon,” says Wadia. What’s more, 20 nanometers of pyrite can absorb as much light as 300 micro meters of silicon. Because it absorbs so much more light, it can be made into thinner cells, which require less raw material.
