Light trapping in thin-film solar cells Solar cell technology has matured in the process of decreasing materials usage and cost while increasing energy conversion efficiency. Enhancing the light-trapping capability of cells promises to do both. Energy © Louis Grenet In state-of-the-art thin-film solar cells, light trapping is typically accomplished through the use of rough surfaces that facilitate total internal reflection. These surfaces increase the optical path of the energy carriers, essentially increasing their retention time in the device and thus increasing the potential for exploitation. Within the EU-funded project AGATHA (Advanced gratting for thin films solar cell), researchers aimed to enhance light trapping. used a modulated surface texture combining a micrometre scale textured glass substrate with a hundred nanometre scale textured back electrode (made of transparent conductive oxide by etching or molybdenum. The double-textured surfaces proved to maximise light scattering in silicon-based and copper indium gallium selenide thin-film solar cells. Researchers developed 3D optical models taking into account the roughness of all cell layers, and the theoretical predictions matched experimental measurements. AGATHA was one of three projects from the coordinated call organised between the EU and India. Despite delays in signing the agreement between European and Indian consortia, project partners fulfilled all initial goals during the project's six-year lifetime. The new technology promises to reduce the absorber layer thickness, resulting in less material usage and cost with increased performance. By increasing the generated photocurrent while maintaining other desirable electrical characteristics, it is expected to have an impact on 70 % of the thin-film solar cell market. Keywords Light trapping, thin-film solar cells, energy conversion, AGATHA, transparent conductive oxide, glass texturation
