Global Sources
EE Times-Asia
Stay in touch with EE Times Asia
EE Times-Asia > Power/Alternative Energy
Power/Alternative Energy??

Iron pyrite holds promise for cheaper solar cells

Posted: 24 Nov 2014 ?? ?Print Version ?Bookmark and Share

Keywords:University of Wisconsin-Madison? solar cell? fool's gold? iron pyrite? photovoltaic?

University of Wisconsin-Madison researchers have found out that iron pyrite, a compound that makes a mineral commonly known as fool's gold, has a number of properties that make it an ideal material for manufacturing efficient, yet less-costly solar cells.

"We think we now understand why pyrite hasn't worked," said Song Jin, chemistry professor at the university, "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, suggested Jin.

A film of iron pyrite, a compound built of iron and sulphur atoms, could be 1,000 times thinner than silicon and still efficiently absorb sunlight.

Fool's gold

Like silicon, iron and sulphur are common elements in the Earth's crust, so solar cells made of iron pyrite could have a material cost advantage in large scale deployment. In fact, previous research that balanced factors such as theoretical efficiency, materials availability and extraction cost put iron pyrite at the top of the list of candidates for low-cost and large-scale photovoltaic materials.

In the latest online edition of the Journal of the American Chemical Society, Jin and first author Miguel Cabn-Acevedo, a chemistry Ph.D. student, together with other scientists at UW-Madison, have explained how they identified defects in the body of the iron pyrite material as the source of inefficiency. The research was supported by the U.S. Department of Energy.

In a photovoltaic material, absorption of sunlight creates oppositely charged carriers, called electrons and holes, which must be separated in order for sunlight to be converted to electricity. The efficiency of a photovoltaic solar cell can be judged by three parameters, Jin said, and the solar cells made of pyrite were almost totally deficient in one: voltage. Without a voltage, a cell cannot produce any power, he stated. Yet based on its essential parameters, iron pyrite should be a reasonably good solar material. "We wanted to know, why is the photovoltage so low," explained Jin.

"We did a lot of different measurements and studies to look comprehensively at the problem," said Cabn-Acevedo," and we think we have fully and definitively shown why pyrite, as a solar material, has not been efficient."

In exploring why pyrite was practically unable to make photovoltaic electricity, many researchers have looked at the surface of the crystals, but Cabn-Acevedo and Jin also looked inside. "If you think of this as a body, many have focused on the skin, but we also looked at the heart," said Cabn-Acevedo, "and we think the major problems lie inside, although there are also problems on the skin."

The internal problems, called 'bulk defects,' occur when a sulphur atom is missing from its expected place in the crystal structure. The defects are intrinsic to the material properties of iron pyrite and are present even in ultra-pure crystals. Their presence in large numbers eventually leads to the lack of photovoltage for solar cells based on iron pyrite crystals.

- Paul Buckley
??EE Times Europe

Article Comments - Iron pyrite holds promise for cheape...
*? You can enter [0] more charecters.
*Verify code:


Visit Asia Webinars to learn about the latest in technology and get practical design tips.

Back to Top