Reliability of copper-ribbons in photovoltaic modules under thermo-mechanical loading

Every temperature change induces stress between the module components due to the thermo-mechanical mismatch, which results in a displacement of solar cells in the module and therefore loads the solar cell interconnectors in between. As a result a limiting factor of solar module lifetime is the fatigue behaviour of these electrical cell interconnectors: the copper-ribbons. The purpose of this work is a quantitative estimation of the thermo-mechanical induced strain in the ribbons during service. For this purpose specially prepared solar cells were laminated to a solar module in an industrial process line and filmed during thermal cycling tests. Finally, the loading conditions on the ribbon were assessed by a previously developed lifetime model based on mechanical fatigue testing procedures.