A long way to go for iron pyrite solar cells

Scientists led by researchers at Sweden’s Uppsala University are investigating the use of cheap, abundant iron-pyrite as a solar cell material.

With a – non certified – conversion efficiency of just 2.8% representing the high-water mark for the material, a determined R&D effort would appear necessary to supplant the use of more costly silicon.

The Uppsala-led team focused on iron pyrite (FeS₂) nevertheless, with the scientists noting several studies have confirmed the material’s solar potential. “FeS₂ offers possibilities of the lowest‐priced electricity production among the known solar cell materials,” stated the Uppsala group in a research paper. They added: “As the raw material cost is a quite small part of the total module and system cost, it is likely that FeS₂ has to reach efficiencies close to existing thin film materials to be economically competitive.”

Sustainable

The Uppsala-led team’s investigation into iron pyrite cells was published in Advanced Materials. The group noted, studies have shown that while the material exhibits many properties which would appear to make it ideal for solar cells – including strong light absorption, high electron mobility and a bandgap of around 0.95 electron volts – performance is limited by low voltage.

In the paper, the scientists explored the physical and chemical reasons for the low voltage. “We are in … dire need of having earth-abundant, non-toxic and low‐cost materials made into thin‐film technologies beyond widely used Si [silicon] for next-generation solar cells,” read the paper. “FeS₂ has the true potential to be the deal-breaker but still faces several challenges.”

The scientists suggested ways to improve the photovoltage of the material through optimization at a molecular level, and noted approaches related to electron-phonon pairing and photon recycling have already shown promise.

However, the paper sounded a heavily-caveated note when it stated: “We believe that it would not be impossible to obtain a high photovoltage with FeS₂ solar cells one day.”