Covering a roof or a wall with standard solar panels changes a building’s appearance – and not always for the better. Architects and building owners now have a choice of two colors for solar panels: black and bluish-gray. Researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering (IOF) in Jena (Germany) aim to give them more design freedom with different panel colors.
The team is currently working on the fundamentals of how to make colored solar cells from paper-thin silicon wafers, which would be particularly suited to designs for decorative façades and domestic roofs. The basic idea is to vary the thickness or the refractive index of the transparent conductive oxide (TCO) layer on the surface of the silicon, which enhances photon capture and provides electrical contact. Dye-based solar modules and flexible organic solar cells also hold promise for increased design flexibility.
So far the team has managed to combine wafer-based silicon with processes borrowed from thin-film photovoltaics. They are also pioneering the use of innovative coating materials. Indium tin oxide is the most common material used today, but it is expensive. The IOF laboratory is working on ways to use cheaper zinc oxide doped with aluminum.
The IOF team plans to use laser-based optical welding to join individual solar cells, since it is accurate at micrometer scale and does not damage the surrounding material. They are also developing an inkjet printing process for connection to the TCO layer on the silicon wafers. This will make manufacturing faster and enhance design freedom.