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Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten. # Peel testing of ribbons on solar cells at different angles: Consistent comparison by using adhesive fracture energies

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Fulltext urn:nbn:de:0011-n-3112749 (155 KByte PDF) MD5 Fingerprint: 3251716d5dd2c1f5ff64ce6409727878 Created on: 7.11.2014 |

**Abstract**

The peel test is a very simple and fast method to determine the adhesion of interconnector ribbons to solar cell metallizations. It is part of the solar cell standard DIN EN 50461 and is, due to its ease of use, widely accepted to qualify cell metallizations and the soldering process. In the standard a minimum force of 1 N per mm of joint width is specified but other relevant quantities are missing, for example the peeling angle. We show that this lack of specification influences the peel testing results. We therefore apply the mechanical theory of Kinloch and Kawashita [1,2] where measured peel forces are translated into adhesive fracture energies GA. The fracture energy is a geometry-independent parameter that describes the energy to break the interfacial bondings at the peel front. It incorporates the dimensions of the ribbon and its stress-strain-curve. We perform 121 peel experiments at 45°, 90°, 135° and 180° of ribbons on continuous front side busbars of cells from one stringing batch. We measure very high forces at 45° (mean value 9.74 N), while the mean values are in the range of 3 N for 90° (3.14 N), 135° (2.46 N) and 180° (3.49 N). The force level at 45° is thus a factor of 4 higher compared to 90°, 135° and 180°. Transforming the force values into adhesive fracture energies, the mean values deviate only by a factor of 0.6 (45°: 510 J/m2, 90°: 395 J/m2, 135°: 441 J/m2, 595 J/m2). This indicates that the method improves the interpretation of peel testing data by using the adhesive fracture energies as mechanical material parameters to quantify the adhesion.