Abstract: A process and apparatus for the manufacture of silicon blocks having a columnar structure comprising monocrystalline crystal zones having a crystallographic preferred orientation. In a casting process, each mold filled with molten silicon is transferred, before the silicon has solidified completely, to a separate crystallization station where the silicon can then crystallize completely. During this process, the exposed surface of the silicon is maintained in a molten state until the end of the solidification process has almost been reached. The process allows the various, necessary steps to be carried out simultaneously and yields high-quality solar cell base material.

Abstract: The invention relates to a process for the direct manufacture of semiconductor wafers, wherein the semiconductor wafers are obtained from molten semiconductor material by providing an area of the surface of the semiconductor melt that corresponds approximately to the size of the wafer with at least one seed crystal, by allowing this area of the surface to cool until it solidifies, the cooling being brought about at least substantially by loss of heat by radiation, and finally, by removing the crystallized-out wafer from the surface. If elemental silicon is used as the semiconductor material, wafers that are suitable for further processing to form solar cells are obtained.

Abstract: The invention makes it possible to manufacture silicon wafers having vertical p-n junctions as the basic material for solar cells. As a result of simultaneously adding certain dopants that act in the silicon crystal as donors and certain dopants that develop acceptor properties and also as a result of measures that result in a periodic change in the crystal growth from a low rate v.sub.n to a high rate v.sub.n, p- and n-conductive zones are produced in the silicon, each having a total length of from 5 to 2000 .mu.m.