That man on the street corner sporting the tin hat and claiming to have conversed with aliens may not be crazy after all; he could have just been demonstrating the sun-absorbing qualities of tinplate, the silvery-white metal element of atomic number 50.

Tinplate, or tin -- as researchers from Northwestern University recently proved -- is cheaper than lead and just as good at absorbing sunlight in solar panel cells. Scientists say it could be the next big thing in photovoltaics.

"This is a breakthrough in taking the lead out of a very promising type of solar cell, called a perovskite," said lead researcher Mercouri G. Kanatzidis, an inorganic chemist at Northwestern. "Tin is a very viable material, and we have shown the material does work as an efficient solar cell."

The solar cell is stacked like a sandwich, and includes five separate layers -- each performing an essential task in enabling the closed electrical circuit to derive energy from sun's rays.

"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," explained Robert P. H. Chang, a materials scientist from the McCormick School of Engineering and Applied Science.

Solar cells featuring lead perovskite have maxed out at 15 percent efficiency, whereas initial tin-based cells only recorded six percent. But the scientists say as they continue to fine tune their new cells, tin perovskite should be able to match or even surpass lead's productivity.

The details of the scientists' work with tin solar cells were laid out this in the journal Nature Photonics.