Study of thin-film silicon solar cell back reflectors and potential of detached reflectors

The back reflector of thin-film silicon solar cells often consists of a textured metal surface separated from the silicon layers by a thin dielectric layer (e.g. ZnO). Despite the high reflectivity of the textured ZnO/Ag back reflector, parasitic absorption losses exist in both the ZnO and Ag layers. In order to better understand the origin of the optical losses at the rear side of thin-film silicon solar cells and study the potential of alternative back reflector designs, a new method is introduced. This method is based on the utilization of a highly conductive n-layer and a local electrical contacting scheme allowing the use of nonconductive rear dielectric layers or media. In this contribution, the cell absorption and the quantum efficiency of microcrystalline p-i-n solar cells with ZnO/Ag and SiO2/Ag back reflectors as well as with a textured Ag back reflector separated from the n-layer by an air gap of a few micrometers are compared.