Tomographic defect reconstruction of multicrystalline silicon ingots using photoluminescence images of As-Cut wafers and solar cells

Photoluminescence images of the side faces of a multi-crystalline silicon brick yield valuable information of the electric quality of the material. However, the signal originates from only the first millimeters of the surface and thus contains no bulk information. If consecutive PL-images of wafers sliced from a whole brick are taken and combined, a tomographic reconstruction of the brick is possible. This approach opens a new insight into the silicon crystallization process and its influence on solar cell parameters. By means of image processing crystal growth, impurities, grain boundaries and defect clusters can be reconstructed three dimensionally helping to identify the origin of certain defects and to further optimize the crystallization process.