Effect of gravity on the microstructure of Al-Si alloy for rear-passivated solar cells

We study the influence of the gravity field orientation on the microstructure of Al–Si forming alloy. Due to the difference between the diffusivity of aluminum and silicon, Kirkendall void formations are normally found at the back of rear-passivated solar cells instead of an eutectic layer. We show that the voids may partially be avoided by sintering the samples with the solid/liquid interface oriented opposite to the direction of the gravity field. A local back-surface-field is found underneath the voids using this approach. This phenomenon strongly applies to rear-passivated solar cells, which exhibited strong fill factor losses.