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Investigations on cracks in embedded solar cells after thermal and mechanical loading

: Sander, M.; Dietrich, S.; Pander, M.; Ebert, M.; Thormann, S.; Wendt, J.; Bagdahn, J.


Nowak, S. ; European Commission:
27th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2012. DVD-ROM : Proceedings of the international conference held in Frankfurt, Germany, 24 - 28 September 2012
München: WIP-Renewable Energies, 2012
ISBN: 3-936338-28-0
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <27, 2012, Frankfurt>
Conference Paper
Fraunhofer IWM ()
electroluminescence; module; cracks; reliability

Cracks in crystalline solar cells in photovoltaic modules can be caused by applied mechanical stresses. To investigate the development of cracks in encapsulated solar cells a new approach was chosen that analyzes thermal and mechanical loading systematically. For this purpose two experiments are established using mini-module specimens with three or 10 cells. It was found by using electroluminescence imaging that after thermal loading small cracks (< 10 mm) were initiated mainly at the beginning and at the end of the busbars. After mechanical loading the cells show complete failure. The crack directions depend on the loading direction. Furthermore it was shown that a loading parallel to the busbars causes cracks at lower load magnitudes than a loading perpendicular to the busbars. The findings can be transferred to full-scale modules by using finite element simulation results. The comparison with other investigations allows an interpretation of many effects that were observed in full-scale PV modules and allows design optimization for reduced cell breakage rates.