>1.8 millisecond effective lifetime in n-type silicon grown by the noncontact crucible method

We evaluate the performance and gettering response of n-type ingot silicon material grown by the noncontact crucible method for photovoltaic applications. As-grown lifetimes are >150 µs and relatively homogeneous through the ingot. We apply standard and extended gettering profiles to elucidate gettering response. Effective minority carrier lifetimes are greater than 700 µs and 1.8 ms at an injection condition of 10
¹⁵
cm
⁻³
after standard and extended gettering schemes, respectively, on samples from near the top of an ingot. Unlike the as-grown state, the wafer lifetime distribution in gettered samples is not homogeneous. In wafers from lower parts of the ingot, concentric-swirl patterns of lower lifetime are revealed after gettering. We hypothesize that gettering removes a large percentage of fast-diffusing impurities, while defect striations similar to swirl microdefects found in Czochralski silicon can in some cases continue to limit lifetimes after gettering. These results indicate that, by application of a tailored gettering process, silicon materials grown by the noncontact crucible method can achieve lifetimes that can readily support high-efficiency solar cells, while highlighting areas for further material improvement.