Surface modifications by wet oxidation method removing getter layer in crystalline silicon cells

Abstract

Reducing the impurity atom content in crystalline silicon (c-Si) can effectively reduce the recombination current density (J₀) and improve the photoelectric conversion efficiency (PCE) of solar cells. Phosphorus diffusion gettering (PDG) has been proven to be an effective method to remove impurity atoms from c-Si. However, the research studies show that the traditional tube thermal diffusion method will cause a large number of dislocations on the silicon surface during the oxidation process, reducing the effectiveness of gettering. In this paper, the wet oxidation method is systematically used to remove phosphorus-rich layers (PRL) and modify the surface. The gettering effectiveness is measured by the minority carrier lifetime (τ_eff) and bulk carrier lifetime (τ_bulk) of silicon wafers. The results show that wet oxidation can reduce J₀ by 27.0% and increase τ_eff by 26.3%. For the bulk region, the average τ_bulk can be increased by more than 6–14%. In addition, with the final PCE comparison, the efficiency of the wet oxidation cell will be improved by 0.12%. These works indicate that the wet oxidation method can significantly improve the gettering effectiveness and the PCE of c-Si solar cell fabrication.