Electrochemical etching of porous-pyramids structure with low reflectance

By anisotropic etching, pyramids structured silicon can be prepared using sodium hypochlorite for monocrystalline solar cells. Their influence on the reflectance of the silicon surface was studied to optimize the etching and reduce the optical losses of silicon surface more effectively. However, currently the reflectance of the pyramids structured silicon surface can only be reduced to above 10%in the visible range, which is still too high for high efficiency solar cells. Porous pyramids structured silicon is a promising antireflection coating to solve the problem of high surface reflectance in silicon solar cells. In this paper, a promising method for fabricating porous pyramids compound structure on silicon surface was proposed. The silicon surface was first texturized in NaOCl/C₂H₅OH and then electrochemically etched in HF/C₂H₅OH solution. The average reflectance of the surface in the range of 500-900 nm was as low as 5%. The surfaces prepared under optimized condition were investigated by Scanning Electron Microscopy (SEM) and Spectrophotometry.