Texturization of monocrystalline silicon for solar cells

A new etchant, sodium phosphate tribasic (Na3PO4&middot12H2O) solution, was firstly applied to texture monocrystalline silicon for solar cells. Uniform pyramids in the wafer of monocrystalline silicon were formed with 3% of sodium phosphate tribasic at 70°C for 25 min. By SEM it was found that the density of pyramid increases with the increase of etching time and reaches saturation. For different etching temperatures and concentrations, the saturated time varies. If the etching time is too long, the top of pyramid will collapse, leading to the rise of reflectance. Although isopropyl alcohol (IPA) plays a great role in the alkaline solution for texture monocrystalline silicon, it makes a negative effect in the sodium phosphate tribasic solution. The mechanism of texturization was discussed. It was found that anisotropic etching is the basic cause of pyramidal formation and defect, and IPA or PO43- is the cause of big pyramid formation. This etchant has the advantages of low cost, no pollution and good reproducibility, so it can be used for large scale production.