As part of a broad partnership, various industry players and research have succeeded in producing thin film photovoltaic silicon capable of reaching a yield of 10% over an area of more than one square meter by optimizing the management of light. The project LIMA (light management for photovoltaic thin-film silicon industry) is supported to the tune of 4.4 million euros by the Federal Ministry of Environment (BMU).
A third of the power module related to managing the light, that is to say, the better exploitation of the incident light. Besides the silicon layer, which converts light into electrical energy, the electrodes are of paramount importance. On the one hand they allow electrical contact with silicon, but they also influence the path traveled by the light beam into the latter. And over this path is longer, the module can convert energy.
The front contact covers the entire front surface of the silicon, and must be as transparent as possible to let the maximum light. It consists of a metal oxide such as zinc oxide. The back contact consists of a second electrode layer and a silver layer that can reflect light.
To lengthen the path traveled by light, the interface between different layers is made slightly rough, so that the rays do not penetrate the module directly but undergo a broadcast. Their path is thus 16 times longer. This roughness is achieved by etching using hydrochloric acid, leaving a crater structure.
The partners in the project LIMA, under the direction of the Research Centre Jülich (North Rhine-Westphalia), were the companies Applied Materials, Sentech Instruments, Sunfilm, Schott Solar Thin Film, Saint-Gobain Sekurit, Malibu Solar and the Helmholtz Centre in Berlin, the Fraunhofer Institute for Technology and surface layers and the Technical University of Aix-la-Chapelle.