Lifetime Enhancement in EFG Multicrystalline Silicon

Presented at the 28th IEEE Photovoltaic Specialists Conference; Anchorage, Alaska; September, 2000. ©2000 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.P and AI gettering and SiN-induced hydrogenation of EFG Si have been investigated using manufacturable process techniques. Annealing of SiN coated EFG, without AI on the back, shows very little defect passivation with maximum lifetime enhancement at 700°C. However, annealing of the SiN film, in the presence of AI, significantly increases the defect passivation and moves the optimum temperature to above 800°C. This increase in the optimum temperature is the result of tradeoff between the increase in the release of hydrogen from the SiN film and the decrease in the retention of hydrogen at defects at high temperatures. A higher annealing temperature (>800°C) is desirable because it produces a superior AIBSF without sacrificing defect passivation. Finally, it is shown that the efficacy of the gettering and hydrogenation process is a strong function of the as-grown lifetime, which dictates the final lifetime as well as cell efficiency