Suppression of light-induced degradation of minority-carrier lifetimes in low-resistivity Cz-silicon wafers and solar cells

This paper reports the recent achievements of the international joint research to investigate light degradation of minority-carrier lifetimes in low-resistivity Si CZ wafers. Twelve kinds of CZ, MCZ and FZ Si wafers were evaluated under AM1.5 irradiation and processed to fabricate solar cells using low and high temperature processes. Lifetime degradation was greatly suppressed using MCZ Si wafers with low-oxygen content and Ga-doped CZ wafers with high-oxygen content. In particular, high-temperature oxidation was also effective to obtain almost no light-induced lifetime degradation in B-doped MCZ and Ga-doped CZ Si solar cells. The Ga-doped, low-resistivity CZ wafers have a potential to realize very-high-efficiency cells irrespective of the low segregation coefficient during crystal growth.