Researchers at the French Centre de Nanosciences et de Nanotechnologies (C2N) have collaborated with researchers at Fraunhofer Institute for Solar Energy Systems (ISE) and others to efficiently capture the sunlight in a solar cell on an ultrathin absorbing layer made of 205 nm-thick gallium arsenide (GaAs) on a nanostructured back mirror. This new process of fabrication achieved an efficiency of nearly 20%.