On the passivation performance of SiNx, SiOxNy and their stack on c-Si wafers for solar cell applications: Correlation with optical, chemical and interface properties

SiNx and SiOxNy layers deposited by the PECVD method are commonly used in silicon solar cells for their excellent thin film properties. In this study, we perform an experimental analysis of the optical, chemical and electrical properties of these films prepared under different process conditions. The C–V measurements for the interface analysis reveal that SiOxNy layers for any refractive index have lower interface state density and fixed charge density than SiNx layers. Additionally, our calculations on the FTIR spectra indicate that SiNx, when compared with SiOxNy, has a significantly higher hydrogen amount which is important in reducing the interface traps. Furthermore, we explain the passivation results obtained from PCD measurement for single SiNx, single SiOxNy and their stack layers on p-type and n-type Si wafers by C–V and FTIR measurements. Our results suggest that depositing a very thin SiOxNy having low Dit beneath SiNx having high Qf and H amount provides superior passivation on p and n-type Si wafers, which is improved further by a subsequent fast-firing process.