Enhancement of diffusion length of pregettered multicrystalline silicon solar cells by hydrogen ion implantation at the end of the process

Abstract

2×2 cm2 n+pp+ multicrystalline silicon solar cells have been fabricated using thin wafers less than 200 μm thick. A large electron diffusion length has been achieved in these wafers after metallic impurity gettering using a heavy phosphorus diffusion prior to cell processing. Further improvements in the electron diffusion length (Ln) and in the short circuit current (Jsc) of these cells are brought out by hydrogen ion implantation carried out through the back surface of the finished cell. A 25% increase in Ln and a 5.5% increase in Jsc are obtained.