Study and mitigation of moisture-induced degradation in SHJ modules by modifying cell structure

Abstract

Silicon heterojunction (SHJ) modules are known for their high efficiency and are expected to gain significant market share in the coming years. In terms of reliability, SHJ technology can be sensitive to moisture-induced degradation and sodium-induced degradation from sodium ions released from the glass. In these degradation mechanisms, the different layers of the SHJ cell structure could play an important role that needs to be understood. This work investigates the moisture-induced degradation in SHJ modules under damp heat (DH) by varying the cell structure with different types and thicknesses of transparent conductive oxide (TCO). Due to the migration of sodium ions, the thinner the TCO layer, the higher the degradation induced. The protective effect of dielectric capping layers is also investigated, allowing at the same time to reduce the indium consumption, which is a crucial issue for SHJ cells. These layers provide protection against degradation. Finally, a schematic model is proposed to summarize the degradation mechanisms, including the effect of cell structure on them.