Method could facilitate cheaper and thinner solar cells

According to a statement from North Carolina State University, making the cells thinner should significantly decrease manufacturing costs for the technology.

‘We were able to create solar cells using a nanoscale sandwich design with an ultra-thin active layer,’ said Dr Linyou Cao, an assistant professor of materials science and engineering at NC State. ‘For example, we created a solar cell with an active layer of amorphous silicon that is only 70nm thick. This is a significant improvement, because typical thin-film solar cells currently on the market that also use amorphous silicon have active layers between 300nm and 500nm thick.’

The ‘active’ layer in thin-film solar cells is the material that actually absorbs solar energy for conversion into electricity or chemical fuel and is sandwiched between layers of dielectric material.

‘The technique we’ve developed can be generally applied to many other solar cell materials, such as cadmium telluride, copper indium gallium selenide, and organic materials,’ said Cao.

The first step is to create a pattern on the substrate using standard lithography techniques. The pattern outlines structures made of transparent, dielectric material measuring between 200nm and 300nm. The researchers then coat the substrate and the nanostructures with an extremely thin layer of active material, such as amorphous silicon. This active layer is then coated with another layer of dielectric material.

Using dielectric nanostructures beneath the active layer creates a thin film with elevated surfaces evenly spaced all along the film.

‘The nanostructures act as very efficient optical antennas focusing the solar energy into the active material. This focusing means we can use a thinner active layer without sacrificing performance. In the conventional thin-film design, using a thinner active layer would impair the solar cell’s efficiency,’ said Cao.