Researchers Create Safety Belt For Perovskite Solar Cells

• NREL and NIU researchers claim to have devised a new sequestration technique to prevent lead used in perovskite solar cells from leaching into environment
• Coating front and back of the perovskite solar cell with lead-absorbing films, the researchers were able to stop more than 96% of lead from leaking into water from damaged cells
• They also found that this does not bring down the efficiency level of the perovskite solar cells and can be helpful in its commercialization

It is no news that lead is a toxic material that officials around the world have been banning from homes and human lives, but it is still needed in case of a next generation solar cell as it forms part of the light absorbing layer in a perovskite solar cell. To deal with its toxicity, researchers at the US National Renewable Energy laboratory (NREL) and Northern Illinois University (NIU) created a sequestration technique with two different lead-absorbing films to prevent more than 96% of lead from leaking into the water from damaged cells.

And, these films did not affect the performance of the solar cell, building the case for commercialization of this technology.

Funded by the National Science Foundation and the US Department of Energy's Solar Energy Technologies Office, the research has been published in Nature journal.

Titled On-Device Lead Sequestration for Perovskite Solar Cells, the research work explores the public health risk and environmental concern with lead toxicity and leaching of this metal from devices as challenges that prevent it from being adopted widely, since lead is an important ingredient to push up the efficiency of a perovskite solar cell.

To put it in perspective, the researchers point out that the highest efficiency of a lead based perovskite solar cell is close to 25%; without lead it comes down to half.

For their experiment, the team coated the front glass side of perovskite solar cell with transparent lead-absorbing molecular film containing phosphonic acid groups that bind strongly to lead. The back side with metal was covered with a polymer film blended with lead-chelating agents between metal electrode and standard PV packing film.

They found that lead-absorbing films on both sides swell to absorb the lead, instead of dissolving when the cell was intentionally damaged with a knife and a hammer and immersed in water thus 'retaining structural integrity for easy collection of lead after damage', preventing more than 96% of lead from leaking into the water from damaged cells.    

"Lead toxicity has been one of the most vexing, last-mile challenges facing perovskite solar cells," said Tao Xu from the NIU. "Our on-device lead-sequestration method renders a 'safety belt' for this fascinating photovoltaic technology."