Improvements in the electrical properties of UMG-Si wafers and solar cells were investigated via the application of a P diffusion gettering process. To enhance the improvements, the gettering parameters were optimized on the aspects of gettering temperature, gettering duration and POCl3 flow rate, respectively. As expected, the electrical properties of both multicrystalline Si (multi-Si) and monocrystalline Si (mono-Si) wafers were significantly improved. The average minority carrier lifetime increased from 0.35 μs to nearly about 2.7μs for multi-Si wafers and from 4.21 to 5.75μs for mono-Si wafers, respectively. Accordingly, the average conversion efficiency of the UMG-Si solar cells increased from 5.69 to 7.03% for multi-Si solar cells (without surface texturization) and from 13.55 to 14.55% for mono-Si solar cells, respectively. The impurity concentrations of as-grown and P-gettered UMG-Si wafers were determined quantitatively so that the mechanism of P diffusion gettering process on UMG-Si wafers and solar cells could be further understood. The results showed that application of P diffusion gettering process has a great potential to improve the electrical properties of UMG-Si wafers and thus the conversion efficiencies of UMG-Si solar cells.

Application of Phosphorus Diffusion Gettering Process on Upgraded Metallurgical Grade Si Wafers and Solar Cells. H.B.Xu, R.J.Hong, B.Ai, L.Zhuang, H.Shen: Applied Energy, 2010, 87[11], 3425-30