On the Hydrogenation of Poly-Si Passivating Contacts by Al2O3 and SiNx Thin Films

Doped polycrystalline silicon (poly-Si), when coupled with a thin SiO₂ interlayer, is of large interest for crystalline silicon (c-Si) solar cells due to its outstanding passivating contact properties. To reach high levels of surface passivation, it is pivotal to hydrogenate the poly-Si and the underlying c-Si/SiO₂ interface. This can be done by capping the poly-Si with a hydrogen-containing dielectric layer such as Al₂O₃ or SiN_x, followed by a thermal anneal. On the basis of recent research, this work addresses several aspects of such hydrogenation by dielectric materials, including the effect of the annealing ambient, the thermal stability and reversibility of hydrogenation, the poly-Si doping level and c-Si surface texture. Additionally, the implementation of hydrogenation of poly-Si by dielectric materials in solar cells is discussed.