Scientists based at Empa, the Swiss Federal Laboratories for Materials Science and Technology, have set a new efficiency record for thin-film copper indium gallium (di)selenid (or CIGS) based solar cells on flexible polymer foils, reaching an efficiency of 20.4 percent. This is an increase from a previous record of 18.7 percent set by the team back in 2011.

Flexible thin film solar cells boast the advantages of both increased flexibility, and a more cost-effective roll-to-roll manufacturing process, when compared to more widespread crystalline silicon-based solar cells. However, they are typically considered relatively inefficient.

The scientists, led by Ayodhya N. Tiwari at Empa's Laboratory for Thin Film and Photovoltaics, cite the breakthrough as a key step to making CIGS-based thin film solar cells more practicable for future widespread use.

“We have now – finally – managed to close the ‘efficiency gap’ to solar cells based on polycrystalline silicon wafers or CIGS thin film cells on glass,” said Tiwari.

The efficiency of Empa's flexible polymer foil-based thin solar cells bests the record of 20.3 percent efficiency for CIGS solar cells on glass substrates, and also equals that of the most efficient polycrystalline silicon wafer-based solar cells.

The next step is to scale-up the technology to be suitable for large scale, roll-to-roll manufacturing, and Empa is collaborating with a start-up company named Flisom to help bring this about.

The research is supported by the Swiss National Science Foundation (SNSF), the Commission for Technology and Innovation (CTI), the Swiss Federal Office of Energy (SFOE) and the EU Framework Programs.

Source: Empa