The effects of grain boundary (GB) character and impurity contamination on the recombination activity of grain boundaries (GBs) in multicrystalline silicon (mc-Si) were systematically studied through an electron-beam-induced current (EBIC) technique. First, clean GBs of various characters were checked at 300 and $100\mathrm{K}$ . The EBIC contrasts of these GBs were in the same range of 0%–2% at $300\mathrm{K}$ and 2%–4% at $100\mathrm{K}$ , suggesting that the recombination activity of clean GBs is weak and the GB character has no significant effect on it. Second, the effect of impurities was studied by comparing the EBIC contrasts of the same type of the GBs in mc-Si with different Fe contamination levels. The recombination activity of GBs became stronger as the contamination level rose. The variation in the recombination activity related to the GB character was also observed in these specimens. The random or high-$\Sigma$ GBs showed a stronger EBIC contrast than the low-$\Sigma$ GBs. Moreover, we found that the EBIC contrast was not uniform along one $\Sigma 3$ GB. In a clean mc-Si, the variation in the EBIC contrast of different parts of the $\Sigma 3$ GB was 1% at $300\mathrm{K}$ , whereas it was more than 10% in the contaminated mc-Si. This indicates that not only the GB character but also the GB plane would affect the recombination activity of GBs. These results suggest that the recombination activity of GBs is principally determined by the gettering ability of GBs. Specifically, that random GBs may have the strongest gettering ability, whereas $\Sigma 3$ {111} has the weakest.

The impact of the boundary plane and impurity contamination on the recombination activity of $\Sigma 3$ boundaries in multicrystalline silicon (mc-Si) was studied by means of electron-beam-induced current (EBIC) technique. In the as-grown contamination-free mc-Si, the EBIC contrast of different $\Sigma 3$ boundaries was in the order of $\Sigma 3\left\{111\right\}<\Sigma 3\left\{110\right\}<\Sigma 3\left\{112\right\}$ . This order may be attributed to the difference in the defect density of the $\Sigma 3$ boundaries due to the effect of the boundary plane. But the maximum EBIC contrast did not exceed 2% at $300\mathrm{K}$ , suggesting that the $\Sigma 3$ boundaries are originally electrically inactive and the boundary plane has no significant effect on their recombination activity. When contaminated with Fe at $900°\mathrm{C}$ , the EBIC contrasts of the $\Sigma 3\left\{110\right\}$ and $\Sigma 3\left\{112\right\}$ increased at $300\mathrm{K}$ , whereas that of the $\Sigma 3\left\{111\right\}$ was still weak $(<3\%)$ . This variation in the EBIC contrast may be related to the effect of boron and it is also indicated that the $\Sigma 3\left\{111\right\}$ has the weakest gettering ability. When contaminated with Fe at $1100°\mathrm{C}$ , the EBIC contrasts of all the $\Sigma 3$ boundaries continued to increase and bright-denuded zones developed around the boundaries. The $\Sigma 3$ boundaries in the $1100°\mathrm{C}$ air-cooled mc-Si showed stronger EBIC contrasts and broader denuded zones than those in the $1100°\mathrm{C}$ quenched one. This phenomenon was explained in terms of the precipitation of Fe. The precipitation of Fe at grain boundaries (GBs) was affected by both the GB type and cooling rate, that is, Fe is easier to form precipitates onto the $\Sigma 3\left\{110\right\}$ and $\Sigma 3\left\{112\right\}$ boundaries during slow cooling.

Transition-metal impurities gettered by grain boundaries (GBs) act as recombination centers of carriers and are regarded to be harmful defects in multicrystalline silicon (mc-Si) used for solar cell production. In this study, gettering of iron by $\Sigma 3$ GBs in mc-Si was investigated by using transmission electron microscopy and annular dark-field (ADF) imaging. In the clean specimen, both straight $\Sigma 3\left\{111\right\}$ GB and zig-zag $\Sigma 3\left\{110\right\}$ , {112} GBs are not electrically active, whereas the zig-zag $\Sigma 3\left\{110\right\}$ , {112} GBs become electrically active when contaminated with iron. ADF images have shown that iron is preferentially gettered at the irregular parts of zig-zag $\Sigma 3\left\{112\right\}$ GB and exists in the form of clusters. The iron gettering abilities of these $\Sigma 3$ GBs have been discussed.