The purpose of alkaline polishing technology is applied to the polishing process on rear side of PERC cell.

1. Can achieve a mirror-like surface, and the cell efficiency increases more than 0.1% compared with acid polishing.

2. No hydrogen nitrate in the process, and no nitrogen emission, be friendly to environment.

3. Alkaline polishing can achieve mirror-like surface which is good for rear side passivation even if the etching weight is lower, more suitable for thinner wafer.