Solar Systems

摘要

By forming a crack that runs parallel to the surface of a silicon (Si) wafer, researchers at Belgium's Inter-University MicroElectronics Center (IMEC) can produce crystalline Si wafers that are thinner than 50um. The wafers will be usable in solar cells. Using mechanical processes and existing screen printers and belt furnaces, scientists can create a crack that causes the wafer surface to peel away in thin layers (Fig. 1). The resulting Si foils offer 25sq.cm areas, are 30 to 50um thick, and potentially may exhibit no kerf loss. Engineers first screen-print a metallic layer on top of a thick crystalline Si wafer, then anneal the item at high temperatures in a belt furnace. Different thermal expansion coefficients for the metal and silicon generate a stress field in the substrate as the material cools. This eventually produces a crack that runs parallel to and near the surface. Ultimately, the top layer of silicon and the attached metal layer snap off from the parent substrate. A metal-etching solution removes the metal layer from the silicon foil. It then is possible to peel other layers from the same substrate.