Laser surface treatment of multicrystalline silicon for enhancing optical properties

To minimise reflection from the flat surface, the multicrystalline silicon wafers were textured. This means creating a roughened surface so that incident light may have a larger probability of being absorbed into the solar cell. Due to grains of random crystallographic orientation, most of the texturing methods used for monocrystalline silicon are ineffective in case of multicrystalline silicon. Therefore, in the present paper a new approach to surface texturisation was developed. Texturisation of multicrystalline silicon wafers was carried out by means of laser surface treatment. Then, a special etching procedure was applied to remove laser-damaged layer. The reflectance of produced textures was measured by PerkinElmer Lambda spectrophotometer with an integrating sphere. The topography of laser-textured surface was investigated using ZEISS SUPRA 25 and PHILIPS XL 30 scanning electron microscopes. The laser treatment and etching in alkaline solution ensured obtaining texture of regular structure that was insensitive to random crystallographic orientation of different grains. The laser processing parameters were adjusted by performing a number of experiments for different values of processing parameters. It is a new approach to texturisation problem of multicrystalline silicon.