Silicon etching in alkaline solutions has been employed for many years, in the fabrication of solar cells. Surface texturisation of crystalline silicon was performed by using different etching solutions. Recently, a strong oxidising reagent NaOCl has been used successfully by several authors to texture the silicon surface. In this work, the effect of the etching parameters such as solution composition on the silicon surface morphology is studied. The surface of etched samples was analysed by scanning electron microscopy (SEM), spectrophotometry and secondary ion mass spectroscopy (SIMS). The results clearly show that the presence of ethanol in the solution leads to the formation of pyramids, while its absence induces the formation of nanostructures (nanowire or nanoneedle).
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/C 2 H 5 OH and then electrochemically etched in HF/C 2 H 5 OH 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.
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