Conductivity and Surface Passivation Properties of Boron‐Doped Poly‐Silicon Passivated Contacts for c‐Si Solar Cells

International audiencePassivating the contacts of crystalline silicon (c-Si) solar cells with a poly-crystalline silicon (poly Si) layer on top of a thin silicon oxide (SiO x) film are currently of growing interest to reduce recombination at the interface between the metal electrode and the c-Si substrate. This study focuses on the development of boron-doped poly-Si/SiO x structure to obtain a hole selective passivated contact with a reduced recombination current density and a high photo-voltage potential. The poly-Si layer is obtained by depositing a hydrogen-rich amorphous silicon layer by plasma enhanced chemical vapor deposition (PECVD) exposed then to an annealing step. Using the PECVD route enables to single side deposit the poly Si layer, however, a blistering of the layer appears due to its high hydrogen content, which leads to the degradation of the poly-Si layer after annealing. In this study, the deposition temperature and gas flow ratio used during PECVD step are optimized to obtain blister-free poly-Si layer. The stability of the surface passivation properties over time is shown to depend on the blister density. The surface passivation properties are further improved thanks to a post process hydrogenation step. As a result, a mean implied photo-voltage value of 714 mV is obtained