The requirements of raw materials(MG-Si) used in this study and the thresholds of single impurity in P-type solar cells up to 14% efficiency are given in the paper.The new conception of plasma etching purity for silicon particulates is put forward which is directed against the purity requirements of solargrade silicon and the characteristics of MG-Si.The immersing possibility of silicon in high energy ions will be increased,and the passivation effect will be eliminated as a result of the sheath thickening.T...