New cheap, environment-friendly solar cell developed

In a breakthrough, scientists have developed a new low cost, environment-friendly solar cell with improved efficiency that uses tin instead of the hazardous lead.
Northwestern University researchers are the first to create the solar cell that uses a structure called a perovskite but with tin instead of lead as the light-absorbing material.
"This is a breakthrough in taking the lead out of a very promising type of solar cell, called a perovskite," said Mercouri G Kanatzidis, an inorganic chemist with expertise in dealing with tin.
"Tin is a very viable material, and we have shown the material does work as an efficient solar cell," said Kanatzidis.

Lead perovskite has achieved 15 per cent efficiency, and tin perovskite should be able to match - and possibly surpass - that, researchers said.
Perovskite solar cells are being touted as the "next big thing in photovoltaics" and have reenergised the field.

Kanatzidis developed, synthesised and analysed the material. He then turned to 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.
The solid-state tin solar cell has an efficiency of below 6 per cent, 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.
"There is no reason this new material can't reach an efficiency better than 15 per cent, which is what the lead perovskite solar cell offers. Tin and lead are in the same group in the periodic table, so we expect similar results," Kanatzidis said.
The solid-state tin solar cell is a sandwich of five layers, with each layer contributing something important.
The first layer is electrically conducting glass, which allows sunlight to enter the cell.

Titanium dioxide is the next layer, deposited onto the glass. Together the two act as the electric front contact of the solar cell.
The finding was published in the journal Nature Photonics.