Midsummer halves CIGS layer on solar cells
Midsummer, the Swedish maker of flexible thin film CIGS (copper-indiium-gallium-selenium) solar cells, has reduced its CIGS layer thickness to 800nm. This is less than half of what other suppliers can offer, according to the company. "This puts the foundation for low manufacturing cost, which further strengthens the business case and attractiveness for Midsummer's thin film CIGS solar cells", said Sven Lindström, CEO at Midsummer.
Earlier this year, Midsummer announced that the company has managed to increase the efficiency of the whole solar cell to 16.2 percent aperture area of the full 156x156 mm cell. Since then, Midsummer has raised the efficiency from 16.2 percent to 16.7 percent on 156x156mm aperture area. With the help of a new aggressive grading of the CIGS layer, they have also been able to thin it out to 800nm; normally the thickness of the CIGS layer is 2000nm.
Most of the light is absorbed in the first 800nm, so for productivity reasons the absorber layer can be kept thin.
A thinner CIGS layer has a number of advantages. CIGS is the most expensive layer in the solar cell; so reducing the thickness has major cost advantages. Also, if the CIGS layer is reduced, the production time is reduced which increases productivity. A thinner CIGS layer also means that it takes less energy to coat the layer. It also reduces the time during which the substrate needs to be kept warm.
"Considering that the solar cell is made on stainless steel substrates, contains no cadmium buffer layer and that the production process is an all-dry, all vacuum process where all layers (including the buffer layer) are deposited by sputtering, this achievement by our engineers is truly impressive. By halving the thickness of the CIGS thin film solar cell the manufacturing cost will be significantly reduced, which further strengthens the business case", said Sven Lindström, CEO Midsummer.
Midsummer's scientists see the opportunity to reduce the thickness even further with a reflective back contact, i.e. any photons that have passed through the CIGS layer would be reflected and have the chance to do work on the way back.
"Our scientists are constantly working on reducing the thickness and they will now start to work on this opportunity. As soon as we are done we will report it. We are always aiming to increase the productivity in our machines while many of our competitors are chasing records, which means their CIGS-layers turn out to be thicker than ours", Sven Lindström concluded.
