ANALYSES OF WARPAGE EFFECTS INDUCED BY PASSIVATION AND ELECTRODE COATINGS IN SILICON SOLAR CELLS

摘要

The price of silicon on the world market has quintupled within the past five years. As a consequence,the wafer producers developed strategies to save costs, e.g. by manufacturing thinner wafers. While in the year 2004wafer thicknesses were about 300 μm, currently thicknesses are around 200 μm. In the future, wafers with thicknessesof 150 μm and below will be processed. Especially the firing step during processing of such thin wafers maylead to a serious warpage of the cells which is due to differences in the thermo-mechanical behavior of silicon andelectrode layer materials. The present handling systems are not adapted for such bows, so that collisions occur andthe breakage rates increase. Therefore, optimized electrode geometries are to be realized in such a way that warpageof the cells is minimized. A numeric model based on experimentally evaluated data was developed to enable the calculationand prediction of the warpage of solar cells having different kinds of metallization geometries. It could beshown that warpage can be significantly reduced by modifying the geometrical electrode configuration.