Scientists at Northwestern University in Illinois have become the first to develop a new solar cell with good efficiency that uses tin instead of toxic lead perovskite to convert sunlight into electricity.

The breakthrough will enable the manufacture of cheaper solar cells, also called photovoltaic cells or PV cells. The tin solar cell is being hailed as "the next big thing in photovoltaics."

The low-cost, environmentally friendly solar cell can be easily made using "bench" chemistry that uses no fancy equipment or toxic materials such as lead.

"This is a breakthrough in taking the lead out of a very promising type of solar cell, called a perovskite," said Mercouri Kanatzidis, an inorganic chemist with expertise in dealing with tin who led the research. "Tin is a very viable material, and we have shown the material does work as an efficient solar cell."

The new solar cell uses a structure called a "perovskite" but with tin instead of lead as the light-absorbing material. Lead perovskite has achieved 15 percent efficiency.

Tin perovskite should be able to match and possibly surpass that. Perovskite solar cells have reenergized the solar energy sector in the USA.

The breakthrough will realize tin's potential for commercializing super cheap solar cells. Tin is an inexpensive, abundant material. It is also non-hazardous and adaptable to a standard manufacturing process.

Tin's use in solar cells would dramatically cut the cost of manufacturing solar cells while easing the geopolitical supply chain issues that plague other solar cell materials.

Tin also has the advantage of being non-poisonous to the public health and the environment compared to toxic lead, which is the common raw material for making perovskite solar cells.

Kanatzidis developed, synthesized and analyzed tin's use in PV cells. He then turned to Northwestern collaborator and nanoscientist Robert Chang to help him engineer a solar cell that worked well.

"Our tin-based perovskite layer acts as an efficient sunlight absorber that is sandwiched between two electric charge transport layers for conducting electricity to the outside world," said Chang, a professor of materials science and engineering at the McCormick School of Engineering and Applied Science.

Their solid-state tin solar cell has an efficiency of just below six percent, which is a very good starting point, Kanatzidis said. Two things make tin special: it can absorb most of the visible light spectrum, and the perovskite salt can be dissolved and will reform upon solvent removal without heating.

"There is no reason this new material can't reach an efficiency better than 15 percent, which is what the lead perovskite solar cell offers," Kanatzidis said.

In the US, cheap shale gas is gradually replacing coal in the electricity market. There are already indications that industries are beginning to prepare for the day when solar and other renewables replace shale gas.