It was shown that the lateral spread of silicon in a screen-printed aluminum layer increased by 1.50μm/C, when increasing the peak firing temperature within an industrially applicable range. In this way, the maximum spread limit of diffused silicon in aluminum was predictable and does not depend on the contact area size but on the firing temperature. Therefore, the geometry of the rear side pattern could influence not only series resistance losses within the solar cell but the process of contact formation itself. In addition, too-fast cooling lead to Kirkendall void formation instead of an eutectic layer.

Silicon Diffusion in Aluminum for Rear Passivated Solar Cells. E.Urrejola, K.Peter, H.Plagwitz, G.Schubert: Applied Physics Letters, 2011, 98[15], 153508