User:Matthias Diethelm/Copper indium gallium selenide solar cell

Conversion efficiency
CIGS is mainly used in the form of polycrystalline thin films. The best efficiency achieved as of September 2014 was 21.7%. A team at the National Renewable Energy Laboratory achieved 19.9%, a record at the time, by modifying the CIGS surface and making it look like CIS. These examples were deposited on glass, which meant the products were not mechanically flexible. In 2013, scientists at the Swiss Federal Laboratories for Materials Science and Technology developed CIGS cells on flexible polymer foils with a new record efficiency of 20.4%. These display both the highest efficiency and greatest flexibility.

The U.S. National Renewable Energy Laboratory confirmed 13.8% module efficiency of a large-area (meter-square) production panel, and 13% total-area (and 14.2% aperture-area) efficiency with some production modules. In September 2012 the German Manz AG presented a CIGS solar module with an efficiency of 14.6% on total module surface and 15.9% on aperture, which was produced on a mass production facility. MiaSolé obtained a certified 15.7% aperture-area efficiency on a 1m2 production module, and Solar Frontier claimed a 17.8% efficiency on a 900 cm2 module.

Higher efficiencies (around 30%) can be obtained by using optics to concentrate the incident light. The use of gallium increases the optical band gap of the CIGS layer as compared to pure CIS, thus increasing the open-circuit voltage. Gallium's relative abundance, compared to indium, lowers costs.