Improvement of saw damage removal to fabricate uniform black silicon nanostructure on large-area multi-crystalline silicon wafers

Abstract

The first step of preparing black silicon solar cells by Ag metal-assisted chemical etching method (Ag-MACE) is to remove the saw damage layer on the surface of diamond wire saw multi-crystalline silicon wafers. The usual way to do this is with a hot solution of KOH. However, the surface of silicon wafers processed in large quantities in this way will have many white spots and stains. These white spots and stains are the saw damage layer that have not been removed cleanly. They affect not only the appearance of the solar cells, but, most importantly, the subsequent uniform deposition of silver nanoparticles on the silicon wafers. An additive containing cyclodextrin and lignosulfonate has been developed in this work. This can remove effectively the saw damage layer and eliminate the white spots and stains on the surface of the silicon wafer. So as to improve the appearance of silicon wafer and make silver nanoparticles uniformly deposited on the surface of the whole silicon wafer. This additive has been proved to be very useful in improving solar cell efficiency, raising parallel resistance and reducing reverse leakage current and so on. Eventually, mass-produced solar cells made by Ag-MACE with this additive have a maximum efficiency of 19.49%, which is 0.46 percent absolutely higher than that without the additive.