Energy efficiency of solar panels has to be improved significantly not only for the energy turnaround, but also for enhancing economic efficiency. Modules that are presently mounted on roofs convert just one fifth of the light into electricity, which means that about 80% of the solar energy are lost. The reasons of these high losses are manifold. Up to one tenth of the surface area of solar cells, for instance, is covered by so-called contact fingers that extract the current generated. At the locations of these contact fingers, light cannot reach the active area of the solar cell and efficiency of the cell decreases.

"Our model experiments have shown that the cloak layer makes the contact fingers nearly completely invisible," doctoral student Martin Schumann of the KIT Institute of Applied Physics says, who conducted the experiments and simulations. Physicists of KIT around project head Carsten Rockstuhl, together with partners from Aachen, Freiburg, Halle, Jena, and Jülich, modified the optical invisibility cloak designed at KIT for guiding the incident light around the contact fingers of the solar cell.

Normally, invisibility cloak research is aimed at making objects invisible. For this purpose, light is guided around the object to be hidden. This research project did not focus on hiding the contact fingers visually, but on the deflected light that reaches the active surface area of the solar cell thanks to the invisibility cloak and, hence, can be used.

Cz monocrystlline silicon furnace produce silicon solar ingot , then machined to solar cells. Carbon carbon composite draft tube , carbon composite crucible and some thermal insulation materials are usually used in this furnace