In June 2010 LIMO introduced a diode laser system exciting photoluminescence (PL) signals for solar cell inspection.

The Fraunhofer ISE (Freiburg, Germany) successfully demonstrated this system applied to bricks, as-cut wafers and finished solar cells.

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The images (see figure 1 and 2 in attached document) of the inspected solar cells were recorded in less than 1 s. The µ-PCD inspection method, for example, needs more than 10 minutes for recording and analysing. This fast measuring speed enables to use the PL method as an in-line process during the full production speed with 100% quality control. Furthermore, the inspection with PL occurs contactless in contrast to inspection with electroluminescence and therefore non-destructive. Thus, the costs for mechanical set-up and the risk of damaging the solar cell are decreased. Additionally, the LIMO diode laser system operates with a single light source compared to other inspection tools using two light sources. That makes the tools more compact and reduces materials as well as assembly costs.

The well defined wavelength of the diode laser allows separating the excitation and signalling light in a better way than an inspection with LED illumination. Therefore, the detection of the PL light is less complex.

All those advantages guarantee high productivity and low cost per tested unit.

For further information please contact Dr. Frank Kubacki (f.kubacki@limo.de) or visit our website www.limo.de. Please visit us at the 25th European Photovoltaic Solar Energy: level 2, hall 2, booth A48.

Background information – LIMO product news in June:

Description of the diode laser system LIMO120-F400-SL808-103:

The 120 W fiber-coupled industrial laser system is combined with a processing head of the IOS00019x-series. This device generates an asymmetric homogeneously illuminated field under 35° angle of incident that fits to solar cell sizes up to 210 x 210 mm. The center wavelength of 790…808 nm is essential for the separation of excitation source and signal light.