Now, 'cheaper, greener' solar cells that use tin instead of lead

Researchers have developed a new solar cell with good efficiency that uses tin instead of lead perovskite as the harvester of light.

The low-cost, environmentally friendly solar cell can be made easily using "bench" chemistry-no fancy equipment or hazardous materials.

Mercouri G. Kanatzidis, an inorganic chemist with expertise in dealing with tin, said this is a breakthrough in taking the lead out of a very promising type of solar cell, called a perovskite.

Kanatzidis said 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, and tin perovskite should be able to match-and possibly surpass-that. Perovskite solar cells are being touted as the "next big thing in photovoltaics" and have reenergized the field.

Kanatzidis developed, synthesized and analyzed the material. He then turned to Northwestern collaborator and nanoscientist Robert P. H. 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 6 percent, which is a very good starting point, Kanatzidis said. Two things make the material special: it can absorb most of the visible light spectrum, and the perovskite salt can be dissolved, and it will reform upon solvent removal without heating.

The details of the lead-free solar cell is set to be published in the journal Nature Photonics.