Black Multicrystalline Solar Modules Using Novel Multilayer Antireflection Stacks

Today multiand monocrystaline solar cells are typically wet-chemically textured and coated with a thin layer of silicon nitride to reduce losses due to light reflection and for electrical passivation of the silicon surface. In this paper we investigate a layer stack consisting of silicon nitride (SiNx:H) with a high refractive index at the silicon interface, an intermediate SiNx:H layer and on top a silicon oxynitride layer with a low refractive index. This SiNx/SiOxNy-multilayer approach significantly reduces reflection in the range between 350 – 1200 nm both on cell and module level. Electrical parameters of mc-Si solar cells and encapsulation losses are presented showing that the SiNx/SiOxNy-stack can improve cell efficiency by 0.24 % (abs.) and module efficiency by 0.08 % (abs.) compared to a SiNx-single layer coating. The stack was designed to give a uniform black color after encapsulation under solar glass and filler sheet. Special care was taken to ensure that the appearance of the encapsulated cell depends little on the total thickness of the stack. An optical model is presented that predicts the short circuit current on a textured mcSi solar cell with multilayer antireflection coating.