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.