SiNXH films for efficient bulk passivation of nonconventional wafers for silicon heterojunction solar cells

Abstract

Hydrogenated silicon nitride films (SiNx:H) deposited by plasma-enhanced chemical vapor deposition (PECVD) have been studied to passivate defects with hydrogen in the bulk of multicrystalline silicon wafers. Extensive analysis of the PECVD process was carried out to identify the parameters that control the SiNx:H material composition and that mainly influence its mass density and hydrogen content. In addition, the incorporation of a hydrogen gas flow is presented as a strategy to increase the refractive index while enhancing the mass density. Satisfactory results in terms of the effective minority-carrier lifetime of the wafers have been achieved with highly hydrogenated SiNx:H films and with slightly hydrogenated films densified by introducing a hydrogen flow, evincing the importance of the mass density in the passivation process. These hydrogenated wafers could be employed in silicon heterojunction solar cell fabrication, improving their quality, reducing their costs, and enhancing their sustainability.