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

摘要

Passivating the contacts of crystalline silicon (cSi) solar cells with a polycrystalline silicon (poly Si) layer on top of a thin silicon oxide (SiOx) film are currently of growing interest to reduce recombination at the interface between the metal electrode and the cSi substrate. This study focuses on the development of borondoped polySi/SiOx structure to obtain a hole selective passivated contact with a reduced recombination current density and a high photovoltage potential. The polySi layer is obtained by depositing a hydrogenrich 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 polySi layer after annealing. In this study, the deposition temperature and gas flow ratio used during PECVD step are optimized to obtain blisterfree polySi 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 photovoltage value of 714mV is obtained.