Systematic investigation of cracks in encapsulated solar cells after mechanical loading

Mechanical and thermal loads on photovoltaic modules (PV modules) lead to mechanical stresses in the module parts and especially in the encapsulated solar cells which can break under a certain load. To investigate the development of cracks in encapsulated solar cells, a novel approach was developed that systematically analyzes the influence of the load direction on the crack directions. For this purpose an experiment is established that tests specimens on smaller scales under well-known boundary conditions. The cell cracks are statistically evaluated and the fracture stress can be compared directly for different crack orientations or different cell types. The test setup is expected to be suitable to systematically investigate the behavior of new cell or module designs or to act as a quality assurance test.For the investigated cells a loading parallel to the busbars causes cracks at lower load magnitudes than a loading perpendicular to the busbars and different cell types show different fracture strength values. The findings can be transferred to full scale modules by calculating a probability of failure for each solar cell. This allows an interpretation of many effects that were observed in full scale PV modules and allows design optimization for reduced cell breakage rates.

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