Scientists at Empa, the Swiss Federal Laboratories for Materials Science and Technology, have announced a record efficiency of 18.7 percent for flexible solar cells. The breakthrough is the result of control of the energy band gap grading in the copper indium gallium (di)selenide semiconductor (CIGS), which is the layer that absorbs light and converts it to electricity. The team used a novel low-temperature deposition technology, and controlled the vapor flux of elements during different stages of the evaporation process for growing the CIGS layer, to achieve this level of efficiency. Ayodhya N. Tiwari, who leads the research team, said, “We have thus shown that this low-temperature process is also applicable on low-cost metal foils such as aluminum or Mild-steel, achieving comparably high-efficiency cells and indicating a severe cost reduction potential with this technology.” Their work has been published in the journal Nature Materials.