Scientists at Empa, the Swiss Federal Laboratories for Materials Science and Technology, have developed thin film solar cells on flexible polymer foils with a new record efficiency of 20.4% for converting sunlight into electricity. The cells are based on CIGS semiconducting material (copper indium gallium (di)selenide) known for its potential to provide cost-effective solar electricity. The team has succeeded in modifying the properties of the CIGS layer, grown at low temperatures, which absorbs light and contributes to the photo-current in solar cells.
Over the years the laboratory has boosted the photovoltaic conversion efficiency of flexible CIGS solar cells time and again, from 12.8% in 1999 – the group’s first world record – to 14.1% in 2005, 17.6% in 2010 and 18.7% in 2011. What’s more, Empa’s new record efficiency for flexible solar cells now even exceeds the record value of 20.3% for CIGS solar cells on glass substrates – and equals the highest efficiencies for polycrystalline silicon wafer-based solar cells
Thin film, lightweight and flexible high-performance solar modules are attractive for numerous applications such as solar farms, roofs and facades of buildings, automobiles and portable electronics and can be produced using continuous roll-to-roll manufacturing processes that offer further cost reductions compared to standard silicon technologies.
Now it is time for the next step, the scale-up of the technology to cover large areas in a cost-efficient roll-to-roll manufacturing process with an industrial partner. For this purpose, Empa is collaborating with Flisom, a start-up company involved in industrialization of flexible CIGS solar cells.