The efficiency of thin-film solar cells based on copper indium gallium diselenide (CIGS) has increased more in the last 3 years than in the previous 15. And as efficiency goes up, the cost of solar power comes down, according to ZSW.

It was just three months ago that the team achieved 22.0 percent efficiency with a cell that outperformed everything the scientists had developed to date, setting a European record in the process. The cell that has increased this efficiency by another 0.6 percentage points was made in a state-of-the-art laboratory coating plant using the co-evaporation method. The Fraunhofer Institute for Solar Energy Sys-tems ISE has confirmed the results.

ZSW's record-setting cell has an area of about 0.5 cm², a standard size for test cells. The institute's researchers accomplished this latest performance boost by improving the manufacturing process at several points, one being the post-deposition treatment of the CIGS surface with alkaline metal compounds being incorporated into this layer.

In the past, efficiency has increased by just 0.1 percentage points a year on average. However, in the last three years the world record has been eclipsed approximately every six months, with an average increase of 0.7 percentage points per year.

With these latest advances in R&D, thin-film cells could soon be a serious contender for the silicon-based solutions that have dominated the PV market for years, states ZSW. As impressive as recent advances may be, however, ZSW researchers still see plenty of untapped potential in the technology behind CIGS solar cells, and Professor Michael Powalla, ZSW board member and Head of the Photovoltaics division, conveys expectations that ZSW could achieve up to 25 percent efficiency in the years ahead.