Swiss researchers have claimed a new world record efficiency of 18.7% for flexible copper indium gallium (di)selenide (CIGS) solar cells on plastics. Flexible CIGS solar cells have the potential to drive down the price of solar electricity because they are cheaper to produce and this latest breakthrough brings them closer to the highest efficiency levels achieved by crystalline silicon and rigid CIGS cells.

"The new record value for flexible CIGS solar cells of 18.7% nearly closes the "efficiency gap" to solar cells based on polycrystalline silicon (Si) wafers or CIGS thin film cells on glass", says Ayodhya N. Tiwari, who heads-up the research team at the Swiss Federal Laboratories for Materials Science and Technology (Empa) Thin Film and Photovoltaics lab.

Beating the previous mark of 17.6% that the same team achieved in June 2010, the new record was made possible by continuing to refine the process for low-temperature growth of CIGS layers and in situ doping with sodium during the final stage of manufacture.

The Empa researchers say this is the first time that polymer films have been proven superior to metal foils (which require additional barrier coatings) as a substrate in terms of efficiency and believe that the results could pave the way for commercial production of CIGS solar modules with efficiencies above 16%. Start-up company FLISOM is working to bring the technology to market.