On the Influence of the SiNx Composition on the Firing Stability of Poly-Si/SiNx Stacks

Industrial TOPCon cells commonly feature a TOPCon/SiNx stack for the passivation at the rear. In this layer stack system, the SiNx needs to function as a hydrogen source during the firing step to ensure a good passivation after firing. Herein, the composition of this SiNx layer is varied, and it is shown that a refractive index of n->-;2 is desirable to achieve proper hydrogenation of the TOPCon layer yielding a J0s as low as 6.6-fA-cm-2 after firing on textured surface. The increased silicon content in the layer does not lead to negative effects when metallizing the samples and instead leads to less metal spiking resulting in an iVOC of 730-mV including the contacts with a low specific contact resistivity of -1-mO-cm2.