Solar

Record Efficiency of 18.7% for Flexible CIGS Solar Cells

Scientists at Empa, the Swiss Federal Laboratories for Materials Science and Technology, have further boosted the energy conversion efficiency of flexible solar cells made of copper indium gallium (di)selenide (also known as CIGS) to a new world record of 18.7% – a significant improvement over the previous record of 17.6% achieved by the same team in June 2010. The measurements have been independently certified by the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany.

It’s all about the money. To make solar electricity affordable on a large scale, scientists and engineers worldwide have long been trying to develop a low-cost solar cell, which is both highly efficient and easy to manufacture with high throughput. Now a team at Empa’s Laboratory for Thin Film and Photovoltaics, led by Ayodhya N. Tiwari, has made a major step forward.

“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 Tiwari. He is convinced that “flexible and lightweight CIGS solar cells with efficiencies comparable to the “best-in-class” will have excellent potential to bring about a paradigm shift and to enable low-cost solar electricity in the near future.”

One major advantage of flexible high-performance CIGS solar cells is the potential to lower manufacturing costs through roll-to-roll processing while at the same time offering a much higher efficiency than the ones currently on the market. What’s more, such lightweight and flexible solar modules offer additional cost benefits in terms of transportation, installation, structural frames for the modules etc., i.e. they significantly reduce the so-called “balance of system” costs.

Taken together, the new CIGS polymer cells exhibit numerous advantages for applications such as facades, solar farms and portable electronics. With high-performance devices now within reach, the new results suggest that monolithically-interconnected flexible CIGS solar modules with efficiencies above 16% should be achievable with the recently developed processes and concepts. 

Sabine Voser is in the Communications unit of Empa, a Research Institute in Switzerland.