Passivated emitter and rear contact (PERC) technology is becoming increasingly common in mainstream PV cell production. A major advantage of the technology is that it can be deployed and an upgrade to many existing cell production lines. However, the technology brings with it some challenges for cell manufacturers including in the inspection of the cell rear side after passivation, laser opening, and firing.
Germany’s ISRA Vision claims to have developed an inspection tool that can accurately detect faults that may occur with the laser opening and contacting process, through deploying light at multiple wavelengths to provide a detailed image of the backside of the cell. The company reports that its CHROME+ process then combines the information from the various illuminations resulting in only "sharply defined contours of a contact or defect" show up.
An advantage of the technique, ISRA claims, is that pseudo defects are not incorrectly defined, and previously undetected print defects show up. This avoids "unsatisfactory classifying," says ISRA.
Alongside the multiple light source CHROME+ technology, ISRA says that its complementary operation software allows for the tailored application of the technology. A CAD-style editor is incorporated in the CHROME+ tool which can define and then apply various parameters pertaining to contacting print shapes, which then can be rolled out across multiple lines. Specific inspection processes and defect classes can be incorporated by manufacturers into the editor program.
"This ensures… easy ramp-up of new production lines and allows for unitary quality standards of a cell type in which all of a manufacturer’s plants and subsidiaries worldwide."