Reduced power degradation in bifacial PERC modules by a rear silicon oxide additive layer

Abstract

In this paper, we investigate the influence of silicon oxide (SiOx) layer on the potential induced degradation (PID) of P-type monocrystalline PERC cells and modules. A SiOx layer was added between the aluminum oxide (AlOx) and silicon nitride (SiNx) layers on the rear side of PERC cells using a newly designed plasma enhanced chemical vapor deposition (PECVD) tool, MAiA from Meyer Burger. The performance of cells and modules with this AlOx + SiOx + SiNx stack was characterized by electrical breakdown (EBD), cell degradation indicator (CDi) and climate chamber PID tests. The EBD test results indicate that the AlOx + SiOx + SiNx stack has higher breakdown voltage than the typically used AlOx + SiNx stack. After undergoing CDi tests, power degradation is more severe in PERC cells with AlOx + SiNx passivation stack than those with AlOx + SiOx + SiNx passivation stack, as evidenced by darker photoluminescence. Bifacial modules made from PERC cells with the AlOx + SiOx + SiNx rear passivation stack demonstrate a significant reduction in rear PID from 12.3% to 4.2%. The results above depict that the addition of a SiOx layer between the AlOx and SiNx layers could effectively reduce the transfer of positive charges from the SiNx layer into the AlOx layer.